[Philyn]

Anyone have any luck boring out .0001 in a bore. I have a bore that is +/-.0001. If it ends up just short I am unable to machine out the last tenth or two. I am using an extremely sharp tool but it seems I can not keep it in the cut unless I take at least .0003. I try to keep it undersized on purpose so I have at least that much left but that is not always the case. It is a 1" bore on .060" wall 316 S.S. tubing which does not help. I am temped just to have them jig ground.

[rlockwood]

.0001 is too light of a pass, its just not going to happen consistently with a boring head.

Is it a through bore?

Leave a few tenths and have it honed.

Get some lapping compound and lap it.

Why does it need to be within .0001?

[Philyn]

I asked the same question but it must be held. It is for a high end instrument. Right now I am going to see about the cost of having them ground to size.

[SCzEngrgGroup]

You two options are honing, or reaming. Either will work, in the hands of a skilled operator. Cutting tools simply can't remove such a small amount, other than by abrasion.

Regards,
Ray L.

[rlockwood]

You two options are honing, or reaming. Either will work, in the hands of a skilled operator. Cutting tools simply can't remove such a small amount, other than by abrasion.

Regards,
Ray L.

a reamer won't hold a tenth tolerance regardless of whose hands it'd in

[fizzissist]

All you're going to do with 316 is work harden it by repeatedly running the reamer thru it... and it won't do the reamer any good either.
A sharp carbide boring bar is one solution, a real touchy one. The other is honing with a fine paste. That's what I'd do.

[holbieone]

Anyone have any luck boring out .0001 in a bore. I have a bore that is +/-.0001. If it ends up just short I am unable to machine out the last tenth or two. I am using an extremely sharp tool but it seems I can not keep it in the cut unless I take at least .0003. I try to keep it undersized on purpose so I have at least that much left but that is not always the case. It is a 1" bore on .060" wall 316 S.S. tubing which does not help. I am temped just to have them jig ground.

nickel stainless steel has a skin that's thicker then .0001 ,the more gummy the material the thicker the skin
i would have it ground , at a wall that thin releasing it from the jaws can put the part out of tolerance

[rowbare]

Have they specified at what temperature these parts will be inspected? When you are dealing with +- .0001 that is a very important thing to know since 10 degrees f can put you in or out of spec. You also have to let the temperature of the part stabilize before measuring it. The cutting action will heat up the part enough to throw your measurement off.

bob

[rlockwood]

Not trying to be mean here, but my assumption is that this job arrived as his door because he was the only one foolish enough to say 'yeah I can do that!" without having any idea how much of a moron the designer was, or how impractical of a task he was being asked to perform.

As a frame of reference, I rarely attempt to hit any tolerances tighter than +/-.0003 directly. Its much simpler to ream a few tenths under and hone to size afterwards. The few exceptions to this rule utilize a very specialized style of "reamer" (its actually a boring bar) that use carbide guide pads to ensure a stable cut. They cost nearly $1000 each, and are very specific in regards to not only hole size, but material and depth of cut. They'll hold +/-.0002 off of the machining center.

I'm curious though, how hard did the grinder laugh?

[fizzissist]

Used to be a guy down the street that did nothing but honing, had 6 Sunnen hones, and he was always busy. Holding +/- .0001 was pretty common for him.