.001-.002 material removel

[pp-TG]

Sounds easy right?

I have some parts here that the operator let go undersize. I need to remove one to two thou out of them the problem is they are O1 Tool steel and they are now 61 Rockwell... Any ideas on how to only take out very little material in very hard material?

Thanks, Travis

[BYTHEBOOKBOB]

I assume that you are talking about holes or internal cavities. If you have holes that are under-size, honing should do the trick. A Sunnen hone is a wonderful machine for such a task. If the holes are blind, you could charge up a brass lap and use that to enlarge the hole with diamond compound, otherwise surface or jig grinding should take care of it. Should you not have any commercial laps, you can turn a piece of brass and roll it in diamond powder with a bit of oil on the surface of it to cause the powder to adhere. Lightly tap the surface of the lap to embed the diamond powder in the lap and presto, you have a very nice lap. Use plenty of oil while lapping and keep moving in and out.

Good luck,

Bythebookbob

[murrayclair]

If this is a die or punch and the dowel holes are too tight you can use a piece of round steel and hacksaw a slot in one end. Then grab a piece of emery cloth and wind it around the steel using the slot as the start of the coil. Then put the steel in the drill press and move it up and down in the hole while the drill is spinning this will take out a thousanth or so. If it requires higher precision you can wire cut or sink EDM.
If the holes are large you can bore with ceramic or PCD or CBN inserts.

[pp-TG]

Thanks for the info guys...

It is in fact a die the holes are .190 and need to be .192 +.002/-.000 not sure what happened but supposidly they were good when they went out for heat treat and they must of shrank this much(acording to the operator)......

so removing with a stick and emery cloth may work but it sounds time consuming on 100 holes any ideas on a much quicker eaiser way or is that the way to go?

Thanks again for you time and help.....

Travis

[RICHARD ZASTROW]

You got it. The hole got smaller because heat treating can cause material growth. The material around the hole grew into the hole. Common problem with gears also.

Dick Z

[Andre' B]

We stopped using O1 it moves all over when hardening, S7 is a lot nicer to work with.

Just get an 1/8 TiALN coated end mill and helex down thru, should be about a minute per part.

350 SFM, and 0.0005" feed per flute, dry air blast

[pp-TG]

Hey thanks for your help guys... We did manage to get them fixed and yes Andre'B we did use a coated end mill to do it....

Thanks again,

Travis

[juergenwt]

Andre - I agree about not using O-1 for precision dies, but S-7 is not for dies except for forming dies or dies having to withstand a high impact. S-7 is a shock steel and should be hardened and drawn to about 53-56RC. It does not have good wear resistance. A-2 (59-61RC) is a better choice and for high capacity dies not having a fragile cross section use D-2 (60-62RC).
Usually holes in O-1 will open up in Heat treating but like Andre said, O-1 while cheap can be somewhat unpredictable.

[Andre' B]

Yep I should have said A2 for dies, just that lately I have been doing a bunch of stuff with S7 so that is what come out of my fingers.