Precision Ground flat stock question

J

J. MacDonald

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Jun 8, 2000
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I just made my first bulk purchase of stainless bar stock so I can start making folders. I bought what to me seems like a lot of steel for a hobby maker, but did so beause I intend to work with one steel for a while to develop my heat treat and consistancy of my processes. The supplier that I purchased it from only had 5/32 stock but I wanted .125, so they offered to have it precision ground for a significant upcharge. Even with the upcharge, the pricing was competitive for the material involved, so I went ahead and ordered 18' to be shipped in 6, 3' bars. The material arrived and had been strapped to a board to make sure it didn't get bent in shipping, but when I cut the banding off the board, I found several of the bars to have what to me is a significant bow to them, perhaps as much as .250 over 2 feet (width of my surface plate). It's probably slightly worse over the entire 3' length. The material is uniformly ground, although slightly undersize at .123, but I am concerned about the bow. I'm not naming the supplier as I haven't contacted them yet and they're generally good people, but I wanted to get some opinions here as to what is considered acceptable flatness for precision ground bar stock. My only other experience in ordering longer bars of precision ground stock was 01 I got from Tool & Die and it was always flat when I received it.

Is it normal to have a bow in thin precision ground bar stock? Does one try and straighten the entire bar, or work on a blade by blade basis as you cut the stock into smaller pieces? I'm looking for advice so I know whether to pursue the supplier to make it right, of if I'm just expecting to much from raw materials. What do you guys think?
 
Much of the thin PG bar stock I order will have a slight, very slight, bow. With folders, I don't think it should give you a problem. I would work with it on a piece by piece basis. In my opinion, you may be making too much of this, but I am not a folder maker, except for early type friction folders.
 
I'll bet they took the existing bars and resurfaced one side only.
That will cause a warp to develop.
 
Howie, that's not it. The stuff was rough blanchard ground when I looked at it at first. What arrived is surface ground on both sides. But you know as well as I that if it was warped when they put it on the mag chuck it can be ground to a uniform thickness, but still be warped when it comes off the chuck. Or it was ground too much on one side which as you note will cause warpage.
 
I'd call them on it, then.
Straightening a bar is a pain, and it should not have been necessary.
 
what would bother me the most is, if you paid to have it ground to .125 and got it .023 ...
it should be .125 + .002 at least for finishing.
for that amont of bow on folders that wonldn't bother me.. but if you paid
a good price to grind it,, you should get a good grind..
 
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