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Straightening

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Anyone know an inexpensive way to straighten cold rolled forms? I finished my forms to within .005 on the grooves with the intention of finishing with a triangle stone. I recently got them out to finish and found they bowed slightly from end to end.  Maybe 3/8" high in the middle when laid flat.  You can see the bow when sighting down the forms. They are still flat side to side. I don't know why I didn't notice this when working on them earlier. It's been suggested I clamp them to a flat surface, finish the grooves, and use them anyway. Being somewhat obsessive about accuracy I know it's going to bug the heck out of me knowing they're not flat. I'm also concerned with planing accuracy.

Barring any way to straighten them, I could use suggestions on alternative types of steel. The one and only supplier in the area can't get stress relieved square stock.  (Wayne Kifer)

My understanding is that Garrisons forms were bowed after someone used them as a pry bar. He stuck a block under one end and used them the rest of his life. Just a thoughtful note.  (Timothy Troester)

This may sound crude, well it is crude but effective, place thin blocks under the form equal distance from the high point and with the high side up stand on the crest of the form. Check to see if you made any progress, if not repeat the process again with slightly thicker blocks under the form and try again  The idea is to creep up on it, not fix it in one shot. I used this process once when I put a sweep in the Mast of a Hobie Cat I flipped in the surf, worked great.  (Don Schneider)

I had the same problem and tried this method when I finished my forms several years ago. It doesn't work well for CRS, at least it didn't work for me.  Then again, I only weigh 185 lbs.  Maybe if you're the size of Bob Nunley it might work.  I got as extreme as supporting my 6' forms at the ends on top of 4x4 blocks and jumping onto them.  The forms just threw me off and bounced right back.  Then I did the arithmetic and figured out that the most error this could possibly introduce was a fraction of a thousandth when planing on the concave side.  I decided to live with it, but the bow in my forms is only on the order of 1/8-3/16".  If you find a solution to the problem, I'd sure like to hear it.  (Robert Kope)

One final thought, you may want to check to see if the warp is in both rails or just one.  (Don Schneider)

I'll probably get shot for saying this, but I don't think a slight bow of 3/8" over six feet should affect accuracy at all.  IMHO, as long as the angles and depth of your grooves are accurate, the strips will sit perfectly well in them.  (Mike Roberts)

Instead of standing on them, maybe you could put them on blocks, on a bench, and draw them down with bar clamps?  (Brian Creek)

Don't worry about forms that are warped along their length, most of us who made forms from the first edition of Garrisons book quickly found that there was an error in the dimensions for the tip side of the forms. The solution was to mill or grind .020 off of one side of the CR steel forms leading to a 1/4 to 3/8" bow in the forms. I kind of wonder if that is how Garrisons forms were warped also. Anyway, lots of well planed rods have been made from warped forms. If you are having problems with the integrity of the glued up sections you should look  elsewhere.  (AJ Thramer)

I just had my forms built per the Garrison specs, also from the first edition.  Where is the dimensional error?  I don't have the book here at work, and I'm in the process of tuning my forms at home.  (Mark Wendt)

They could almost be in an S shape as long as the groove is correct unless you plan on laying the glued blank in the form to let it cure straight which it wouldn't IF the form was almost an S shape.  Meaning I can't see it matters.  (Tony Young)

Your problem and all suggestions of the list sound familiar. I'd just like to add one thing: heat that da**d steel up to 1000°C and let it cool off slowly.  (you should have done it before working your a** off on this uncooperative bar of iron.  (Michael Mueller)

I would not invest 1 hour of work on a set of bars that were not stress-relieved.  I've seen some parts here in our plant that were machined and complete.  Then they dropped the part and it distorted in a way that simply boggles the mind.  Not just simple brinelling of the part at the point of impact, but the whole part went haywire....

When tracing back the heat lot of the steel, it was found that they left out the stress-relieving.  Mechanical shock, temperature variations, who knows what else, can set off an internal "explosion" within the steel's crystalline structure.  It's horrific, and I could imagine how I'd feel after investing 50+ hours (like I have in my forms), only to have them rendered unusable due to internal stresses....

I would say that would be the most critical property of the steel that you purchase.  More important than minimum yield strength, elongation, Charpy's impact resistance, corrosion resistance, etc.  Find another supplier if he can't get you stress relieved bar.  I would agree with all the  posts that  say they'll  be fine to use as-is, but my concern would be that the surfaces may not stay flat to each other, the groove may not stay perpendicular to the surface   (twisting),   etc.   down   the   road.  Guess  I'm  a glass-half-empty sorta guy when it comes to materials.....(Troy Miller)