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Measuring

Have you ever noticed any difference between, planing form setup, depth measurements made with the 60 degree point on you dial indicator and  measurements made using the calibrated wire method and the dial indicator;  (where D=(1.5 x d)-h)? If so, which do you feel is the most correct? And did you check these measurements against your dial caliper measurements of the cane strip you just planed? OR, is this a question nobody wants to talk about??   (Don Greife)

    What magnitude of error  are  we  discussing  here?   0.002"  or 0.020"?  Between the compressibility of the bamboo, imperfect geometry (do you have perfect 60 degree angles?), and calibration (how did you zero your 60 degree point?), and accuracy of the instruments, it's nigh impossible to get dead on from just setting the forms. 

    As the other reply to your message stated:  Set them to the numbers, plane a test strip and compare actual to  the settings, then adjust if needed.  You can always slide the strip up the forms (or down) to gain or lose 1 or 2 thousandths.

    For this rod, focus on consistency in measurements and angles.  If you can get all three measurements on a strip to agree within 0.002" and have your angles very close to 60 degrees, and have all the strips average within 0.004" at each station, you will be doing well for your first rod.  I had a bigger problem maintaining 60 degree strips than I did  hitting the dimensions on my first rod.

    How far off are your dimensions and which ones are the closest. Are the angles dead on 60 degrees?

    Wire?

    Actual Strip?

    60 degree point?  (Kurt Clement)

      Kurt has asked some pertinent questions.  I, too, find that holding perfect 60's is more challenging than getting the measurements correct.  I remember Chris Bogart stressing the importance of equal angles several times in past list communications.  At that time, I didn't pay much attention.  But I've gone back and reread those notes several times since.

      Lemme make a suggestion.... Develop a routine for measuring each station on each strip.  I start at the largest station, with the butt end of the strip down.  I first measure with the enamel facing to my right, with caliper in my right hand and strip steadied by my left hand.  I then reposition the strip so that the enamel faces left, and measure again.  Finally I measure with the enamel against the right hand jaw of the caliper.

      If the first and second measurements are equal I'm thrilled.  If the first number is larger, then the plane must be leaned to the right to correct the angle.  Stay with me now... If measurements number one and three are both larger than measurement two, the pith apex is placed to the right, and the plane leaned to the right.  But, if measurement one is larger than both two and three, then the enamel side is placed to the right, and the plane still leaned to the right.  Obviously this is easier to show than to describe.  Equally as obvious, if measurement two is the largest, then the plane must be leaned to the left.

      I correct angles in 5" increments, working 2.5" each direction from each station.  Well, to be candid, if two or three station in a row are "off" in the same direction, I'll work all of them at the same time.  Oh yeah, be sure to correct angles when you have .030" to .060" left to take off at each station, or you'll wind up with one measurement too small every single time.

      Get those angles equal, and measurements become much more reliable.  (Harry Boyd)

      I'm a little puzzled. I have heard of others having problems with angles, but I never have. I'm wondering if a grooved plane helps in this regard - that is the lower sides work like guides and help keep the plane parallel to the forms as the strip approaches final size. It also could be that if you aren't flattening the enamel side the strip isn't getting seated into the groove securely and rocking a bit? Just speculating....

      Let me also say that I've always used a clamp and two handed the plane, even when I was using a 9 1/2. Keeping the plane flat to the form is easier with two hands on the plane - and much easier with a small bench plane.  (Darryl Hayashida)

        As usual, you've hit on several important points.  I think a deeply grooved plane does help somewhat by giving some semblance of outriggers.  I suspect the reason you’ve never had any problems are that you are careful when roughing out, and your use of two hands on the plane.

        I've really struggled with keeping angles correct for the last 6-8 rods.  My thinking right now is that it's important to start final planing with perfect 60's, or you'll fight the angles all the way down to the forms.  (Harry Boyd)

          I had problems maintaining the 60 angles until I started using grooved planes. Like Darryl, I also plane off the enamel when roughing which, to me, was a big help in maintaining the angles. If the enamel side isn't flat it doesn't fit into the form right and you will fight the angles forever.

          Rather than training wheels for the plane. I put two strips of masking tape on the sole of a plane to see if I wanted to invest in grooved planes. It work so well I used the masking tape trick for about a year before investing in  grooved planes.

          IMHO grooved planes and flat enamel sides give perfect 60 angles from start to finish.  (Don Schneider)

          One Thing to remember when planing.  Once you get a triangular shape then each pass of the plane must  be counted.  The same amount of bamboo on each pass. I generally take two passes per side.  Once the strips are smooth enough to take a single pass from one end to the other.  I start sighting the apex.  and make my corrections as I go.  I rarely have trouble with off line apexes, except on the very butt end, and since I cut off a lot of that, I don't really care all that much.  I have never felt the need for a grooved sole.  (Ralph Moon)

          As I am still considering myself new rod making, I have to agree that having the enamel side flat before finishing the final planing is the answer. I found this real early in  the game. I plane the strips till the enamel side is fairly narrow. Turn the enamel side up and scrape it  flat. Scraping the strip when the enamel side is narrow keeps from removing any power fibers to speak of.  With the flat side in the form, the other sides end up flat also. I have no problems with angles or glue lines.

          We all have our own ways of doing things, this is my way.  (Tony Spezio)

        A quick and dirty way of starting out right can be the use of a center gauge.  One with fine lines that are darkened is better, such as the Starrett.  What I did, before switching to the Morgan Hand Mill, was to jam the rough 60'd strip into the gage apex first with my thumb, then hold the strip vertical with the gauge at or below waist level, and look down onto it.  The confluence of the thumb on the bamboo enamel makes a fairly fine line which either does or does not line up equally across the lines of the gauge.  It is remarkable how accurately the eye can detect the slightest variance.  That procedure always helped me get off to a good start which seemed to hold throughout the remainder of the planing.  I think your advice about checking the three apexes later in the task if good, sound advice for which my procedure is not a substitute, just an early enhancement.  (Richard Tyree)

      If you have access to old issues of the planing form, you might want to look up and article written by John Bokstrom about "training wheels" for your plane to keep it level.  it's been a long time since I've seen it, and don't remember the details.  (Chris Obuchowski)

        I looked up that article just yesterday.  The only thing that bothers me is drilling holes into the body of the plane.  If you don't set up properly and your holes are out of alignment, your training wheels could hold the plane at a slight slope rather than flat on the form.

        I'd like to see an alternate method of attaching the wheels so you can ensure that everything is true.  Maybe one that would allow some adjustment.  (Tim Wilhelm)

          I made a variation to the "training wheels".  It is a small slide made from red oak.  I drilled one hole through the plane to fasten the "training slide".  I placed a flat piece of wood (red oak) on top of the slide for the heal of my hand to rest on.  I finished by sanding with sandpaper on a glass.  The plane rested on the glass and the slide just on the sandpaper.  I sanded until the bottom of the slide was true to the bottom of the plane.  As long as I don't let one side of the plane lift, it stays flat.  I don't have a drawing but if there is interest, I could measure and make one.  (Onis Cogburn)

    I don't think that there is any real secret to this , though I  think that if you take a lot of time over your first strip, and are prepared to reset your forms fractionally to take up any inconsistencies in  the setup while you do this first strip, then you will find  that the subsequent strips will go a lot quicker and more easily. That's what I do, and the accuracy of my strips and blanks is certainly better than my capacity to measure the errors.

    My old father-in-law makes a few cane rods; he is 85, and has always been one of those men who thinks he can judge thousandths of an inch more accurately by eye than you can measure them. In point of actual fact, the most precise work he has ever done has been accurate to about the nearest parsec, but he holds firm to this belief in any case!

    He has an old set of aluminum forms made from box sections, and it is set more or less by eye, by guess and by the grace of God.

    And yet, if you ever put a mike on one of his blanks, you will find that at the 5" stations they  are not all that far out.

    How does he do it ?

    He attacks the whole job with a bench plane, a couple of wood rasps, an electric planer and a flotilla of really cheap and nasty block planes; there are bamboo and aluminum  shavings all over the place. And he measures the 5" stations with an old dial caliper that I gave him, with the result that the blank may in fact look like the petrified donger of a Tyrannosaur, but by God, at every 5" point it conforms with relative consistency with whichever nominal Garrison taper he is parodying at the time.

    He glues them with white glue, splices bits in every which way with ditto white glue, ties on with sewing cotton whatever guides he can find around the shed or the garage sales, and finishes with a single coat of two part epoxy, applied by the "bottle and balloon"  with the bottle moving at  about 30 miles per hour.

    They look like a whale spewed on them after a bad night out on Bundaberg rum and  krill pizzas .

    He also has this fly tying technique which I suspect involves coating a hook with super glue and standing back three yards and pelting  the contents of the vacuum cleaner filter at it and then sticking it in a blender with a whole chicken for about 30 seconds before classifying the flies (he has only 3 classes of fly - big, small, and shitty)  and letting them dry  for a couple of seconds before shoving them into a fly box.

    How does it all work?

    I have fished with him for thirty-some years, and have never known him to break a rod other than a bought graphite, have never been able to cast a line as far or as well  as he can, and on about half of our outings he outfishes me significantly, landing his fish (2 to 4 pound range wild brown trout from both rivers and lakes) quickly and with a minimum of fuss.

    Makes me wonder,  sometimes! (Peter McKean)


Several list members have asked about the inexpensive digital calipers I ordered from Harbor Freight, so I thought I'd give a report.  Service was slow, as it almost always is with Harbor Freight.  I ordered on May 14.  The calipers shipped on May 30, and arrived last Friday.

I used the calipers all weekend, and have mostly good things to say.  They are easy to use and read, and measure consistently and accurately.  My only hesitation is that they are rather large, a little larger than my 6" dial calipers.  I've grown used to my 4" digital calipers, and prefer them in most cases, simply because they are smaller and lighter.  All in all, I'd recommend these calipers without reservation.  (Harry Boyd)

    I will second what Harry says except for size.  I am used to a 6" so I didn't notice any difference.  I have a 4" but since I started with a 6" I reach for a 6".  A couple of neat capabilities Harry didn't mention.  To change from English to metric is the push of a button.  Also, the indicator can be zeroed anyplace on the scale so that further movement yields the difference.  Zero the indicator at the measurement of one strip and read the difference for other strips.  Also, mine came with an extra battery.  Thanks Harry!  Your post was a good tip.

    Harry, I got mine a little quicker than you.  I ordered after you posted and got mine in a week earlier.  Haven't got used to it yet.  I am still grabbing my old one.  Can't comment on accuracy except it reads the same for a measurement as my old one, but it is Asian import also.  (Onis Cogburn)

      Sounds like I picked up almost the same caliper, but mine was on an auction at eBay.  I think I paid $34 with shipping.

      I have to admit that it's a heck of a lot easier (and quicker) for me to measure with the caliper than with a micrometer.  Of course, I don't use them everyday, so that could be part of  it.  (Todd Talsma)

    So far I like them. I've found that I'm a bit more picky about precision than I was with the dial calipers. I guess the digital readout and weight of the instrument has a psychological effect. Or maybe it's just me.

    In any case, thanks to Harry for suggesting  this.  (Tom Bowden)


After the fishing season I have started planing. Somehow I have resulted in measuring both the height and width (w = 1.15 x h) of the strips. I even think that it is easier to measure the width when the strip is in the V-Groove. I have not found any comments on possible source of errors by measuring the width instead of the height. Any comments?  (Tapani Salmi)

    I have used a set of calipers to measure the width of strips as they were held on the anvil of a Morgan Mill.  I have since changed to a caliper and V-block.  When measuring the width of the strips the caliper jaws are closing on two acute angles.  It seems to be easy to measure the strips as smaller than the actual dimension.  Another potential problem with measuring the width is that it can be difficult to ascertain that the caliper is perpendicular to the base of the triangle (the enamel side of the strip).  When measuring strip height the enamel is resting against one jaw so it is relatively easy to be certain the angle of the caliper or micrometer is appropriate.  (Bill Lamberson)

    Theoretically it shouldn't make any difference however I believe there is more chance for error measuring the width of a strip to determine it's depth. You are looking for the dimension from the enamel side to the apex,  so why not measure it in the first place?  (Don Schneider)


You can't trust the point of your dial indicator to be a "perfect" point.  I've checked mine and its short .008". 

The 1.5 figure used with a round pin is a function of the geometry of an equilateral triangle.  With the pin sitting in the 60 degree groove the distance from the bottom of the groove to the top of the pin is always 1.5 x the pin diameter.  This is true if the pin is tangent to the sides of the vee groove.  A pin has an effective range of .75 diameter to  1.5 diameter,  so you need different sizes.  (Ted Knott)

    I love math as much as the next guy, but.... I just set my forms a couple of thousandths big, plane, mic,  then make the appropriate adjustments.  Even when all my stuff was bang on, I still needed to make adjustments.  (Tom Ausfeld)

      But how do you measure accurately? No matter how gentle I am, I can't measure a strip and get consistent results. The apex is just too delicate not to compress a few thousandths. I've used calipers with a light touch, a micrometer and a V-block. Same inconsistent results. I never precisely know what the blank is going to measure until  after sanding  off the glue.  It's usually close,  but  rarely dead-on. After 10 or so rods, I still haven't developed that touch that allows me to precisely measure strips.  So I rely on precise setting of the forms. Problem is, I still haven't gotten the hang of knowing when to stop planing. Using a plane or a scraper, I get chatter from the iron scraping on the metal forms, resulting in oversize strips and uneven edges. Using a razor blade for the last few thousandths, I usually end up with undersize strips  (somebody explain to me how THAT happens!).

      I hesitate to post this because I'm nowhere near the point of being within +- .001 on my finished blanks that so many strive for. Am I the only one who has to resort to the sanding block to get close?  (Bill Hoy)

        This is how I do it. This comes from John Bokstrom. My dial indicator base has a slot mill into it that sits over the strip. I use the flat surface of the tip of the dial indicator and place it on a glass plate or the surface of a the table saw to set the dial indicator to zero. While the strip sits in the form you place the slot of the dial indicator over the strip and it will measure the amount of the strip that protrudes over the surface of the form. When the dial indicator indicates zero you are right on the money. You never have to use the caliper on the strip which means you do not have to lift the strip.  This method also allows you to measure every inch of the strip and not just at the stations.  (Adam Vigil)

        I am certainly no expert and my technique may be a little unorthodox but here is what I do.  As I mentioned before I have wood forms and use test strips to set them.  I purchased some digital calipers which I think help me get better reading because it is easier to read.  I plane my strips till my strips are with in .01 of final target, then I go to a hand held scraper usually a sharp plane blade and work from station to station scraping it to final dimension.  Once all of the strips  are done I tape them together and as I would a final blank.  I measure each station across all three flats, write them down and average them.  I them compare them to my target and have either a plus or minus for  each station, then go and make corrections as needed.  I  do not think my system is the fast method, but it seem to work pretty good for me.  I finished a butt section yesterday day and it measured with in .002 of my target at each station.  (Tim Stoltz)

        Using a razor blade, which is flexible, there is a tendency for a curve to develop which will cut below the planing form. Use a Sears scraping tool which has a rigid blade. You may get better results.  (Lee Koeser)

        Not long ago I was in the same boat.  One thing that has helped me measure accurately is a set of calipers which slide very smoothly and easily.  I hesitate to mention that they are cheap digital calipers, from China, via Lea Valley.  But they are very accurate.

        Using the ratchet mechanism, again set very lightly, on my micrometer also works well.

        Use a light touch, and practice repeatedly.  You might practice for a few minutes trying to get repeatable measurements on something solid like a drill bit.

        I know that's got to be a frustrating problem for you.  Keep looking for a solution and you will find it.  (Harry Boyd)

          My $100 Mitutoyo digital caliper does have a very stiff action. Maybe I should have invested less.

          The ratchet mechanism on my micrometer is still way too stiff not to compress fibers. I can get a much better reading with a very light touch, but it isn't repeatable  A tech at Starrett offered to adjust the ratchet by cutting the internal spring, but I never sent it off as I had just ordered a V-block which I had high hopes for. With either a caliper or a micrometer, you still have the problem of making sure that the anvils are absolutely square to the strip. Any skewing will result in a bad reading. Hard to keep it straight when you are balancing a long strip, especially at the tip. I need another hand and much better eyes.

          The V-block just didn't work for me, though I'll admit I probably didn't give it as much of a workout as I should have. Fiddly to set up, and you had to take it off every time you wanted to measure something else.

          As you can see, I've invested a lot of money in trying to solve this problem. I hope it will resolve itself as I invest more time. (Bill Hoy)

            I have two calipers. I leave the v block on one. the only problem I have with the block, is taking measurements smaller than 35 thousandths anybody know why that is?  (Mike Canazon)

              The best set up I've found on the V-block (which I love) is to put it on a digital caliper with a memory function.  The caliper I use is the Mitutoyo Digicalc Absolut (not sure of model #).  It is not the top of the line but still costs about $100 bucks on sale in the tool flyers which you will receive every two weeks if you buy anything.  I think there are fine digital calipers for less, perhaps someone will speak out.

              a.  Mount the V-block taking time to ensure that the top of the caliper which goes into the V-block is 'square' to the 60 degree  triangle (not necessarily the bottom of the slot!).  It took awhile to set it up right and I never take it off.

              b. Now put a known test strip in the block and zero the caliper. (example: Using a .200" strip, put it in then zero. Should now read  0.0000" with  the strip in)

              c. Take the test strip out and run the caliper down to the negative number of the test strip.  (example: pull the strip, run the caliper down till it reads -0.2000")

              d. WITHOUT MOVING IT, Zero it again.  (ex.:.: zero it to read 0.000"). 

              e.  Measure the test strip again and the calipers should read the measurement of the test strip. (ex.: should now read 0.2000" with the test strip in.)

              OR, use a ground drill rod or ground dowel pin and use trigonometry to calculate what the reading should be (like you would in setting forms with a dowel/drill rod).  Use the method above only substitute the rod for the test strip.

              Of course my rods look like hell.  (Rick Crenshaw)

              Same here. Actually, I have three sets of dial calipers. The solar powered, digital Mitutoyo is dedicated to the V-block. The others are dial readouts. A caliper is normally only good for getting one in the ballpark, as there is much room for error. The less expensive Chinese calipers are just fine, and won't break the bank buying them. I can't imagine taking the V-block off and on all the time.

              I recently  received   Tom   Morgan's   nifty   3-in-1 V-block. I set it up on the calipers, used a drill rod to calibrate it, and was done. I checked the drill rod diameter using a .0001-reading micrometer, then extrapolated the necessary information. When it was all said and done, the V-block and micrometer agreed within .0002. Close enough for  this rodmaker.

              Mike, I suspect that perhaps the cutout for the caliper jaw extends too far past the V-groove, thus preventing you from measuring beyond that. I've never had a problem measuring small strips, whether on the Waara or the Morgan V-block.  (Martin-Darrell)

                I made my own V-block from 2 short pieces of drill rod and some trig. My purpose was to find out how much I crush the apex without it. I concluded that its about .001; that is, my strips measured .001 under  the true size  without  the V-block.

                As   has   been   mentioned  on  this  list  before,  a V-block is  only  accurate   if   your  angles  are dead-on 60 degrees.  Depending on the design of the V-block, a 57 degree or 63 degree angle will introduce a lot more error than crushing the apex by a typical 0.001. IMHO, I get better measurements without a V-block and adding .001 than relying on all my angles to always be 60 degrees. My angles get better with each rod, but there are always places where they are not perfect.  (Frank Stetzer, Hexrod, Taper Archive, Rodmakers Archive)

                  Very good point, Frank.

                  Were you getting the crush you estimated with a micrometer or caliper? One other point,  which might be obvious, is that the V-block will help predict the final width of the hexagon whether it be strip  height or angle error.  (Jim Utzerath)

            You will get much more accurate readings from even the cheapest dial caliper if you don't even bother measuring the strips from the enamel side to the pith apex. This is the softest section of the strip and a measurement there is pretty much meaningless. Measure with the two sides as the base of the triangle and a side/enamel corner as the apex. It will also help you to get your finished section dimensions where you want them if you make your sections long enough to trim them where the numbers match the taper you are looking for. I typically make mine at least 2" longer at each end, if not more at the but end. This is enough, with the glue I use and the tolerances I try to maintain, to let me get as close as I want to the desired taper, unless I think it could do with a bit more "wood", in which case I just trim em where I feel like it and to blazes with the original. Most old tapers need a bit more gumption for the modern world anyway. As always, JMHO.  (John Channer)

          I have 2 micrometers, one digital, one analogue. The digital instrument portends to offer measurements in .00001", and the variation on repeat cane measurements is usually of the order of 5/10000". The analogue item depends on me for the final reading, and  thus does not encourage me to think in terms of tenths, let alone hundredths.

          What usually happens is that I do all the pedestrian measurements with digital calipers, and I only read 3 decimal places; when I am feeling obsessive, I check with the micrometers. Perhaps not surprisingly,  the measurements are not often out to any significant degree, and then not due to any equipment error.

          It is my considered opinion that if a rodmaker is working with bamboo, these hypersuperyoubeaut micrometers are about as much use as a hip pocket in a singlet.

          Different thing for those amongst us who do a lot of precision work using metal as an adjunct to their actual bamboo  work. But I, for one, cannot even conceptualize a hundred thousandth of an inch, let alone do something with one.

          I  think that calipers are about ten  times as accurate as I am.  (Peter McKean)

            It's true.  Almost ANY caliper (dial or digital) will give readings that are better than the tolerances we can maintain through our planing and/or sanding efforts.  The variations in caliper readings (from the least-to-the-most expensive instrument) are so subtle that they cannot be rendered serviceable by even the best rod maker.

            It's the care you take as a maker, and not caliper variations in the order of .0002" that distinguish the best rod.  Think about it - even if your caliper regularly misreads by as much as .005" (extremely unlikely), this would translate into an "error" in your finished rod of only .001".

            On the other hand, if you can consistently build rods whose 5" station measurements and flat-to-flat dimensions are within 002" of your taper design, you are great maker!   And it's not because you have a great caliper.  (Bill Harms)


I had a hard time figuring out in my mind why setting your dial caliper to .1155 and setting your dial indicator to zero worked. For those of you as dumb as me,  I hope this file helps.  (Don Schneider)


I got my depth gauge, a Mitutoyo digamatic so I don't have to think about what the dial says but just read the numbers from the display.  I'm not well versed in using these things so I need a little guidance in their proper usage.

Certainly at face value the easiest way to set the gauge to zero is to set it on a flat portion of the form and press the button.  But as I recall setting the 60 degree point on a surface like that can cause damage to it and in time cause inaccurate readings.

Wayne's book talks of a index fixture or block that can be used.  I can't find one in any of the catalogs that I have and after talking to a couple people they have no idea what I'm talking about.  (That probably makes two of us.)

So my question to the list is how is a depth gauge set to zero properly and what sort of procedure do you use to get accurate measurements.  (Tim Wilhelm)

    Now that's a great question.

    I think that the easiest way to do it is to get a piece of drill rod of exact, known diameter and use it as a standard.  A piece in the 1/16 to 1/8" range would be  a good  choice (I keep two sizes).  Through the generosity of the math gods, the height of the rod is exactly 1.5 times the diameter.  So, if you put the 1/16"  (.0625") rod in your form, it will lie even with the surface of the form when the form is set for a section of .09375 inches.  Now you can adjust your depth gauge to indicate -.09375 if it does negative reading or +.006625 if not.

    Once you manage to mess up a large number of strips, you can save those and use them to help set the forms by finding the measurement of the strip you want tot set and set the form so it just fits.  that can save a lot of time.  (Jerry Madigan)


At the risk of coming off as a complete dolt (and I must apologize to Winston Binney and Ralph MacKenzie who walked me through this) can someone give me the blow by blow on how to calibrate my dial indicator. How do I know whether or not it is off?  Do I just start it off "theoretical zero" plane a strip and then measure it with the caliper to find out?  I feel like if I could just get over this hump I might actually be able to do this!  Howell says in his book that "this should be obvious" which really makes me feel stupid! Anyway thanks again in advance for rescuing me from my self imposed despair!  (Mike Janik)

    Let me take a stab at it,

    Be sure you do not bent, dent,  blunt the tip of your 60 degree tip. Gently place your dial indicator on your metal form with the 60 tip touching the

    flat area. Your base should be adjusted on your dial indicator to allow it to be able to this. When you have your dial indicator in its base with the tip on the flat part of the form you will set the face of the indicator to zero with the needle. Tighten the face and now you are at 0. If you are using rods to measure just take off the tip and repeat the procedure above. You can then place the 60 tip in the groove of the form and measure the depth. You typically will be reading it backwards. On a lot of indicators it is the inside red numbers.   (Adam Vigil)

    I sent this awhile back and am reposting it as some were kind enough to say it helped. Rereading it I see it's necessary to mention the "calibrator" is a small block of metal with a 1/8" hole drilled to a depth such that the 60 degree point can't possibly hit the bottom (will rest on its shoulders).  (Art Port)

      Art, if I may be so bold as to add to your instructions.  Lacking a gauge block with a "reamed hole" one can use a caliper to accomplish the same.  Simply set it at 1/8" (or what ever diameter you choose to work with), set your indicator on it and proceed.  (Gary Heidt)

    The easiest way I found is to set you calipers to .1155.  Set the 60 degree point in the .1155 caliper gap with the indicator block flat on the caliper blades. Rotate the face of the dial indicator to zero, tighten the face set set knob.

    I have had no problems with getting the right depth in the forms using this method.  I do not take credit for this, a machinist friend put me on to it.  (Tony Spezio)


So what separates a 30$ dial caliper from a 200$ caliper, besides the price. Are 200$ ones that much more accurate?

The reason I ask, is I am using a dial caliper to measure the gap of my Penrose forms as I am filing the 60* groove, and I notice that if I wiggle the caliper a bit I get an increased reading.  What I have been doing is taking the highest value I can get with whatever wiggling I do. Anyone else have these experiences?  (Mark Bolan)

    I hope you get some intelligent responses to this question.  I've wondered about the same thing.  One way I test calipers is to repeatedly open and close them, seeing if they return to "0" each time they are closed.  I have no idea of the validity of that test, but those that do return to "0" each time seem pretty consistent to me.

    In thinking about measuring the distance between bars, I suspect that the wiggling allows the calipers to find a point where they are truly perpendicular to the forms.  Might not hurt to set a square next to the calipers, and just "eyeball it" to make sure you're not measuring at an angle.  (Harry Boyd)

      I think that is necessary. Also, I do the same with .25" and .5" to see if I get the same reading each time. I do this each time I pick them up, and with my depth gauge. I have worked at calibrating instruments before. One must validate the readings constantly. repeatability is very critical and is one difference between between the lesser and the more expensive instrument, generally speaking.  (Timothy Troester)

        What do you use for the .25 and .5 inch measurements?  Drill rod?  (Harry Boyd)

          I use drills or I have some standards I bought at a flea market. actually for our purposes the device can be a random dimension once the outside measurement and a mid measurement have been verified. if there is an error you want the error to be the same throughout the range of the instrument you are measuring with. I also have some tool steel stock that I measured when the device was new and I wrote the dimension on the piece of stock and checked against these each time. I think repeatability is the most important feature of a measuring device.  you can deal manually with a constant linear error but if you don't have repeatability or linearity you don't have anything.  (Timothy Troester)

      To check for slack in a caliper, measure something at the tips and at the back. If they are not the same perhaps the little screws on the top of the caliper can be tightened to remove the slack.  (Dave Norling)

    No the more expensive aren't more accurate, at least for the problems you described.  I have a Mitutoyo digital and had the same problem you described during my first two attempts at make a form.  The difficulty seems to increase the narrower the gap.  Plus the place where the gap is the narrowest is also the deepest cut in the groove.

    Another factor is that the inside faces of the two pieces to the form may not be perpendicular to the top or bottom of  the form.  Remember you are hand filing the surfaces and are basically "eyeballing" your work to determine the final results before cutting the groove.  In the end this shouldn't matter since it is the groove that needs to be square to the planing surfaces of the form but it seems like it would give you inconsistent readings as you set the gap.

    For my third try at a usable form, I set the gap between pieces using my depth indicator.  Because I made and used a file plane rather than just the file glued to a block of wood I was able to adjust the depth of the file rather then adjust the gap between the bars.  I really don't know who to credit for coming up with that idea but it really makes a difference in my mind.  (Tim Wilhelm)

    There is a big difference between $200 calipers and $30 calipers. The higher priced calipers are very much more precise and there is no play in the action. However, there sometimes are small set screws that can be used to adjust the calipers using an allen wrench and there are the screws on the top of the calipers to take the wobble out of the arms. One way to check the accuracy is to take a feeler gauge and measure it. Check that the arms are contacting the gauge at the tip and bottom.  (David Sullivan)


Maybe someone could explain to me, what is the difference between a dial depth gauge and the dial depth indicator?  I am trying to procure the last of the tools I need for finishing my planing form and I would like to know if I am getting the right thing?  Also, does anyone know a good source for a standard for calibrating the gauge?  (Aaron Tester-Hall)

    They are one and the same. You will need a 60 point and a holder for the DI. To calibrate, go here.  (Don Schneider)

    Probably don't need to bring this up, but when you look at catalogs and stuff you will see a dial indicator and a dial test indicator.  You probably have noticed the difference, but if not, the dial indicator measures vertically while the test indicator measures side to side, sort of.  The dial indicator has a vertical plunger that we use to set the depth of our forms with a 60 degree point installed.  The test indicator has a kind of lever that hinges at the bottom to measure when something is not true, say the run out on a lathe or table saw blade or something.  (Jason Swan)

      A depth gauge with a 60 degree point installed is used to measure the depth of the groove in your planing form.

      A dial indicator can be used for setting the planing form using drill rod blanks. (The depth of the "V" groove is equal to 1.5 times the drill rod diameter minus the dial reading.)

      The drill rod method is the most accurate for setting the forms as the rods will span a distance of 2" or so, while a 60 degree pointer is subject to any "chatter" or other irregularity caused during the milling or filing of the grooves. If you want to check the accuracy of your grooves, for example, use the 60 degree depth gauge and slide it along the groove in the form and watch the needle to see if it bounces.  (Ron Grantham)

    They are the same thing. They are both depth gauges. You will need a 60 degree point to use for setting the forms. As far as a standard, the best and easiest way to set the gauge is using a caliper. Open the caliper jaws to .1155. Set the 60 degree point in the .1155 gap with the gauge block flush on the caliper jaws. Set the dial to zero.

    That is all there is to it.  (Tony Spezio)


I've been a big fan of the inexpensive 4" digital calipers sold by Harbor Freight for several years now.  They don't last forever, but at $15-20 a set I have just replaced them.  Yesterday I tried to order four new calipers and was told that Harbor Freight no longer carries ANY digital calipers in any size.  Makes me wonder what's going on, but that is beside the point.

Might any of you know another source for inexpensive digital calipers?  I like to keep a few sets on hand for newbies, rodmaking students, etc?  (Harry Boyd)

    Little Machine Shop has their 6" electronic calipers on sale for $19.95.  (Mark Wendt)

    I hope we are talking about the same thing, 6" composite digital caliper item # 93293-1JNB Harbor Freight because they have at least 99 in stock as of 5 minutes ago and they're on sale for $9.99.  (Doug Alexander)

    I bought a set of six inch digital calipers from my local Car Quest auto parts for $19.99.  (Aaron Gaffney)

    I bought a digital caliper and digital depth gauge from Harbor freight just a little over a week ago.  I had my choice of four different models of calipers and they were all on sale.  (Ralph Moon)

    www.highlandhardware.com   (Doug Hall)


Question for those of you who use V-blocks.  I made 2, one in Delrin and one in aluminum (because I thought the Delrin one wasn't working correctly.)  If I measure a strip, it is about .008" bigger in the V-block than if I just use the calipers.  I measured a completed tip section in the V-block and compared it to a reading from my micrometer - dead on.  I looked at the strip with a 7x magnifier and can't see any crushing of the apexes.  Am I missing something?  I don't want my next rod to be 15 or 20 thousandths undersize.  (Neil Savage)

    I have the same problem with my V-block, but the error measuring is constant. The nice aspect using the V-blocks is that the measuring is easy and quick. So, the solution is to subtract the constant error to your measures. All the measure instruments are affected by an error. The important point is to know this error and to be sure that the error is constant and not random.  (Marco Giardina)

    I stopped using V-blocks some time ago for the reasons you stated. To me it was just another opportunity to have a measuring error. Besides, how do you know you are measuring the strip at the exact location the taper calls for? Wouldn't it be better to check the strip for size it's entire length?

    What works best for me is to make sure all 3 sides of a strip are even with the top of the form groove for the entire length of the strip. Result- The section comes out to be the exact taper called for and each strip 60.  (Don Schneider)

      Thanks to the former V-block users who responded.  I'm glad it's not just me.  The theory is fine, so I wonder why it doesn't seem to work in practice.  (Neil Savage)

        I like the V-blocks, particularly before the final planing to see how close I'm getting. They also show you the triangularity: if the sides aren't even you'll see a gap between the strips and one of the sides.

        Mine pretty much agree with a second caliper as well as the what the depth finder is telling me.  (Henry Mitchell)

        I could also be that your angles are not dead nuts on 60.  If they are a little less than exactly 60, your strip will ride slightly higher in the V block.  Was the measurement the same for all three sides of the strip at that location?   (Mark Wendt)

          Let me state the following, since several of you have suggested the same things as possible sources of trouble: 

          1) I relieved the bottom of the V with a saw when I made the blocks. 

          2) I get the same measurement using 2 different drill bits, which I measured with my micrometer to get the diameter.  I also get the same measurement using either V-block. 

          3)  I adjusted the angles on the strip by scraping with my 60 degree angle gage. 

          4)  I get a correct measurement on a hex section, but not on a strip. 

          5)  The measurement on the scrap strip I'm using to test ARE the same on all three sides.

          It seems to me that if the V were off I couldn't get a good reading on the hex section since it would be canted in the V.

          I'm puzzled.  If it weren't for the principle of the thing, I'd give up and go modify my roughing  beveller.  (Neil Savage)

            With the strip in the V-block, are you seeing no light at all on the sides, or the top when you close the caliper?  Does seem kind of odd that if you have dead nuts on 60 angles, and the sides are of identical length, that the measurement from flat to apex would be .008" high.   (Mark Wendt)

              Well, I'm not perfect, but there's no light I can see.  Certainly not .008". I don't even know if I'm missing something or not.  Quite a few others have had trouble with the V-blocks, including commercial ones.  (Neil Savage)

                I've never really played around with the V blocks. I've seen them at the Gatherings, but never really used them before.  You said those were V blocks that you had made?  You mentioned that when you put a hex section in the block that it read correctly.  Maybe we're looking in the wrong direction.  I wonder if there might be a small burr near the bottom of the V block that only makes contact with a triangular strip, and pushes it up by that .008"?  If the hex section sits down in the V, and you get the correct reading, it's got to be something that would be affected down below the sides of the V where the hex section makes contact.  How deep and wide did you make the relief at the bottom?  (Mark Wendt)

                  The relief on the aluminum block is cut with a hacksaw, about 1/64" wide and deep.  No burrs on either block.  The Delrin block was relieved with a model railroad track saw, not quite as wide, but about the same depth.  Also, if the strip were hitting bottom, it seems like I should see light on at least one side where it doesn't seat in the V, or the strip should rock in it.  My 60 degree gage fits the V as near as I will ever get it too.  (Neil Savage)

                    After reading your description, I strongly suspect there is something amuck in the way you "zero-ize" your caliper with the V-block.  Maybe one of you with some instructions from John Long can tell Neil what the caliper should read with a certain size piece of drill stock???  (Harry Boyd)

                  The  measurement of a drill rod will be 1.5 times the diameter, but be careful.  Unless the V-block straddles the caliper on both sides of the jaws (and is perfectly aligned side to side) the drill rod will tip and give you a false reading.  (Ron Larsen)

                    It's 1.5 X diameter.  I turned a piece of brass to .125", so the setting is .1875.  Also, I get a correct reading if I measure a completed rod (no question of crushed apex there.)  I'm wondering if the apex ISN'T really as sharp as I think it is.  By the way, John Long  couldn't make it work either.  (Neil Savage)

    I also like the V-block method. It sounds like you have some  sort of problem going on. I would first make sure that the apex of  the groove is perfect. Measure a strip as it comes off your forms,  then remeasure after taking a couple plane passes on the strip apex.  If the numbers are different, there's your problem. Use a jewelers  saw to cut a small slot in the apex of the V block to eliminate the  interference.

    If that is not it, use the drill rod method to check the angle of the  V. Use two rods, one that sits deep in the groove, and another that  sits high. If you calculate a different depth with each rod, the  angle of the V is wrong.  (Tom Smithwick)

    I'm not completely comfortable with the V-block method. I've been using it for 4 or 5 years. The main problem I encountered was with the apex of the groove. I think if you don't cut it away somewhat you are not only susceptible to the V block being inaccurate and under sizing your strips. Also inaccuracies in you bamboo apex get piled up in the groove also knocking off your numbers on the small size.  The other headache is the digital caliper I use and its ridiculous level of accuracy. I think life would be a lot less stressful if I was using a manual version.  After you groove your apex then you can struggle with correcting your angles because the v block really demonstrates your plane control more than any other way I've tried. You'll know when your out of angle.  (Dave Rinker)

    I have a "V" block that I bought from list member John Long several years ago and it has worked perfectly since I took it out of the box and set it up with the 0.125 rod that was included.  I use it with a standard dial caliper and the instructions say to install the "V" block on the fixed jaw of the caliper and insert the .0125 rod and close the caliper jaws firmly against the rod then loosen the dial locking screw and set the dial to read 87.5 remove the rod and use.  It works!  For digital calipers the directions are different.  After you install the  "V" block and insert the rod close the jaws and set the caliper to zero.  Remove the "V" block and set the caliper to read -1.875 (note that this is a minus reading!) Again reset the caliper to zero and reinstall the "V" block and start measuring.  I don't understand that at all, but that is what it says to do so I suggest that you try it if you have not already done so.  I can't speak to the digital calipers, but my dial calipers work just fine with the "V" block. (Hal Manas)

    As a guy who is somewhat new to the "art", but a tool and instrument maker, the problem with the V-block is very simple.

    When planing or machining, you will always create a burr at the edge of the object.  If you place the strip into a V-block with that small burr, it will cause a buildup in the apex, and possibly causing an incorrect reading.  The way to avoid that buildup is either to relieve the strip at the apex or the V-block.  I would hold out for creating a small slot/relief in the apex of the block. If your strips are planed accurately and your angle is correct, you should end up with a correct reading on your caliper.

    Thanks to all of you for some great info and pleasant reading.  (Steve Culen)

      Well, as I stated somewhere in the discussion, I did relieve the bottom of the V when I made it.  I used a small saw and on one block the relief is about 1/32", the other about 1/64".  The theory is nice, I just can't make it work in practice.  I'm going to plane out 6 strips and tape them together then measure and see how far off I am, or if the V-block is really working as expected and my current tests are off somehow.  (Neil Savage)


Some time ago Floyd Burkett sent me the figure for setting the gap on dial calipers to then zero my dial indicator. I've lost the saved email, probably when reverting my hard drive to repair some problem. Floyd seems to be absent, hopefully gone fishing, <G> so if someone could send that figure I'd appreciate it.  (Wayne Kifer)

    .1155.  (Tony Spezio)


This past spring I had a very good friend and aspiring rod maker (he is now one of the clan) spend a few days here at my home.  He was doing so well, I just turned him loose and the poor guy busted his bucket to produce about 5 blanks.  They looked great until we put the micrometer to them.    All were seriously oversized.  I was at a loss as to the reason, but I consoled my desolated friend by stating that these were not failures that they were learning experiences and that I was sure that the mistakes would never be repeated.   We were able to salvage some of the blanks although they did not come out to the original specs we had planned.

I has just assumed that the problem was simply that my friend had made mistakes setting the forms.  It was only yesterday that the full explanation for the disaster became apparent.  I had last summer just purchased a new digital depth gauge, and it was that device that my friend had used to set the planing forms.  Now I have never relied on the depth gauge to set the forms, but I do use it to approximate the setting.  I always use a freshly prepared strip of bamboo to make the final setting.  In other words, I use the depth gauge to get close and the bamboo marking strips to achieve the final size.  I guess I had not made this clear to my friend and he used the depth gauge only.  While this could have given him a pretty good shot at the actual size, the 60 degree tip on my depth gauge had been worn so excessively that it was no longer a tapered point but rather a rounded cone.  No way it could be even close on the finer settings and only marginally close on the larger settings.  I never thought to check for wear on the point, and I wonder if I am alone.  The point apparently wears super rapidly on the CRS planing form.  From now on I intend to search for real cheap points and inspect and replace them often.  (Ralph Moon)


I have a Mitutoyo depth gage for which I just purchased one of the Catalano magnetic bases. It is quite a bit deeper than the previous base and now I can't adjust it to zero as it stops when the dial hits the top of the base. When I turn the dial to change the setting the thousandths hand moves, but it doesn't appear to move the hundredths hand. I could grind a recess into the top of the base so that the dial would clear, is there another way of adjusting the setting?  (Henry Mitchell)

    Sounds like you need an extension.

    Go to McMaster Carr and search for extension rod or Catalog Number 20625A132.  (Larry Blan)


I have been hunting for the last 2 weeks for a 60 degree tip for my dial indicator.

Last weekend I drilled the push and pull bolts on my hardwood forms, they are looking good so far, nice and flush.  To finish them I need a tip for my dial indicator.

I live on the West Coast of Scotland, and have had no luck in hunting one down.

Do any fellow UK rodmakers know of where I can get my hands on one?

Or if anyone would like to sell me one email me off the list.

I am looking forward to getting the forms finished, and getting onto the next stage of this rodmaking journey.

I bought a cheap piece of 2.5" x 6'  cane from local DIY store last week just to experience splitting down a piece of cane. It went well, split straight down the middle. Tomorrow I am going to split it into required strips, so better watch the fingers, going by the horror stories you guys write.

The cane wall is a  quarter inch thick, so it is ideal to practice on. Before I purchase the real McCoy...."Tonkin".  (Alistair Dunlop)

    Starrett makes them.  I contacted the for a part # when I was looking for mine.  (Lee Orr)

    Barry Grantham from Lincoln will be able to help you.  (Paul Blakley)

    You can find what you try to, at Mitutoyo UK.

    Conical point 60   4-48                     art. 101190

    Conical point 60   M 2,5x0,45            art. 101120 

    (Gabriele Gori)

    If you have a look at eBay (UK) you will see Barry Grantham has a set of  forms for sale at the present time.

    His forms are quite popular here in the UK and the set I have is so robust you could use them to lift a TANK! (Paul Blakley)


 

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