Sharpening geometric chasers?

We have several sets needing sharpening. Previously they just bought
new ones when they were dull but this doesn't make sense if we can get
them sharpened relativly cheap. What we have are 8-32, 10-32, and
6-32. The only place around here(Arkansas) that did it no longer does
them so besides an idea of the cost I'm looking for some suggestions as
to where to send them and maybe how long it takes to get them done.
I've heard there is a fixture you can buy and do it your self.
Anybody know anything about this? I have a surface grinder and can
grind radiuses on the wheel.
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$ and its yours.
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middle of page on the right
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of good info on chasers and grinding fixtures]
Reply to
F. George McDuffee
You might try
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if a more local source doesn't turn up. They claim to offer fast turn-around times.
Geometric used to publish a catalog/manual that had some re-grinding info in it and you might try them to see if they can still supply it. AIR, there are at least of couple of fixtures that Geometric sold for re-grinding.
Reply to
Mike Henry
To some extent you can resharpen chasers if they are not too worn. On Geometric Chasers the leading edge is a flat surface that is usually about halfway down the thickness of the chaser. Simply line the chasers up and regrind that surface in one pass.
You will lose some of the depth since the cutting teeth are tapered back. You will also lose some of the depth because you have defined a new cutting surface that is not on center with the work, however a Geometric Die Head usually has about 0.050" of adjustment so in all likelihood you can readjust for the small loss.
Obviously the method is limited to one or two regrinds. When you regrind, you want to create a slight positive rake to the teeth. If they started with a positive rake (common on small sizes), then you want to increase it to ensure that the cutting points are cutting and not pushing.
If you've broken some of the teeth it probably doesn't matter. If you've broken a lot of teeth or if the wear is significant, then you might be able to reclaim the chasers by first grinding the teeth down and then recreating them. When you grind them down, don't grind them off completely, just grind them down the minimum that you can get away with. You can then use the stubs to realign the blanks and reform the cutting teeth - remember that each chaser is offset by 1/4 thread (on a 4-chaser head).
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