Bamboo Tips - Tips Area
Form Setup - Taper Accuracy

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Let me throw this out to see how others are achieving their goals. Lets say I have a taper, and the tip, for example is .063. We have to take into consideration varnish thickness, glue, and final sanding. In order for me to hit my finished target of .063, what must I set my form at. I also scrape my enamel before I  plane the final taper. Anything else that needs to be accounted for in setting the form?  (Mark Bolan)

Getting precise takes a little experimentation and probably won't be achieved on one's first attempt.  I make my calculations for varnish first.  If the rod from which the taper was taken had "normal" varnish thickness, we'll assume .004".  That makes our target for bamboo only .059", right? On tips, you'll have less glue thickness as someone shared last night.  Perhaps your glue lines will add .002"  Subtract .002 from .059 and we're down to .057"  Divide that in half (.0285") and make another decision.  You can set your forms at .028" or .029".  I always set my forms at the larger dimension rather than trying to fool with 1/2 a thousandth.  Taking off half a thousandth while sanding away excess glue is so common as to be almost normal.

To complicate this further you only need to add in measurements from an unvarnished blank.  (Harry Boyd)

Doesn't the measurement for the rod also include the glue thickness in the taper measurement.  (Patrick Coffey)

Yes it does.  That's why I deduct a little bit for glue thickness in setting my planing forms.  If you concede that glue must add something to the dimensions and then make your bamboo exactly 1/2 of the finished rod dimensions, your numbers will not add up.  Your finished rod will be larger than the rod used as a basis for your taper.

We have discussed several times whether or not glue adds a measurable amount to the finished rod section.  I cannot see how it is possible for the glue to add nothing.  (Harry Boyd)

I agree if there is glue there there must be thickness, but the question is how much and does it matter.  Daryl says that the joints have to be less than .001, because he can detect a gap of .001.  Assume then for argument‘s sake.  .00l  Does that amount over the whole taper affect the final action of the rod?  If so, is it really perceptible?  If not, then why not forget it? It is just adding one more layer to a process that is subject to so many variations, that it it is hard to keep all of them straight.  Just my inquiring mind?????  (Ralph Moon)

Wouldn't whether you plane at 60 degrees or the folks at 61 or 61.5 degrees or so also make a difference in the final form setting as to computations? On the 61 or more angle the allowance for glue would probably be minimal as the glue should fill the small gap left?

Also, on the same subject, if the apex of the triangle is planed off, doesn't that affect the entire figure also? It would seem to directly affect "starved" joints or lessen their potential I would think. See what you guys started?  (Dewey Hildebrand)

I do plane off just a bit of the inside apex. It does let the splines fit together a lot better.  (Darryl Hayashida)

If You don't, You'll get glue lines for sure!  (Danny Twang)

Well it all depends. If you have the taper taken from the planning form, or mill pattern then you want to hit that number in final planning. If the taper is taken off a rod then you must allow for the varnish and glue. Now here is the problem when some makers think they can make accurate reproductions. Cane will adapt and fluctuate to its environment and change its dimensions as it does so. Glues lines do exist and most of us have no idea what the width of a glue line is in a rod that is measured. Also glues will shrink over time decreasing the width of the glue. So when a maker simply allows for varnish he is missing the exact measurements. So if you are getting your numbers from Wayne Cattanach’s book you want to hit those numbers exactly. If you are measuring from a rod a little guess work is involved.   (Adam Vigil)

One issue is whether to scrape the enamel off the strips before or after planing. If you sand or scrape the enamel off first, your final taper will be more accurate. However, you need to be more careful with your sanding if you do it that way.  You may have to oversand to get the glue off.  If you leave the enamel on, it is harder to get the taper exact, but you have more flexibility in getting the glue off without going into the power fibers.

If this is your first rod, I would suggest leaving the enamel on, and adding 2 thousandths per strip. one thousandth accounts for the enamel that will be removed, and the second thousandth allows for the slight radius that exists on an unscraped strip. You will have a bit of leeway in terms of getting  to the taper. You can remove cane, but you can't put it back on ...

Now, if anyone out there thinks this is bad advice, please correct me publicly.  (Jeff Schaeffer)