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Profile honing butted ID? Is it a thing and if so what's the process?

Springy

Plastic
Joined
Oct 22, 2021
Anyone got any experience with honing of ID profiles? What I'm specifically looking for is a way to hone a mostly cylindrical profile that gradually tapers (about 1.5 degree taper) about 2/3 the way into the bore. It'd have about 10" depth of bore with a cylindrical profile, about 1.250 diameter, before tapering in to about 1.200 (dims are just for example - exact dimensions aren't actually determined yet). The larger cylindrical bore is where the tolerance and surface finish needs to be held tight for a sliding surface, the tapered part is for structural reasons so both tolerance and surface finish requirement are looser on that, but it does need to be reasonably smooth to eliminate stress risers.

Is there such a thing as a form hone that would be able to do that? I've only ever seen them as cylindrical but it's not something I have much experience with. I imagine I'd need a form tool (like a partially tapered reamer or similar) to rough out the initial geometry and make sure that only a small amount of material is left for honing? I think even with a damped boring bar the total length of the part (about 20") is much too great of a L/D ratio to be able to bore that geometry.
 
You could try a rigid hone for the straight part of the bore then a spring-loaded hone for the back, feeding it so that it followed the contour. Apart from that I can't think of a very good way to do it other than ID grinding.

And I very much doubt that there is any boring bar that could manage that L : D ratio reliably. And even if there were, it would likely be astronomically expensive.
 
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Is this bore blind or do you have the same taper coming from the other side and meeting in the middle? If tolerance is not critical on the taper you could knock it down with a series of flex hones. What is the material?
 
We have done something similar but it was low quantity and much smaller in size. Like 5/16" ID tapered to 1/8" over 1.5". We made a mandrel with the same taper out of hardened steel and used a diamond paste to polish. Wasn't quick by any means but it got the job done.
 
Is this bore blind or do you have the same taper coming from the other side and meeting in the middle? If tolerance is not critical on the taper you could knock it down with a series of flex hones. What is the material?
Material is 7000 series alu. It’s not blind, it’s a tube, but one end is thicker than the other, the taper/butting is a noncritical aspect that joins one tight tolerance larger diameter and one medium tolerance smaller diameter together. I had considered drawn and butted tubing and then just honing the cylindrical part, but that doesn’t lend itself to higher volumes/automation very easily.
 
You could try a rigid hone for the straight part of the bore then a spring-loaded hone for the back, feeding it so that it followed the contour. Apart from that I can't think of a very good way to do it other than ID grinding.

And I very much doubt that there is any boring bar that could manage that L : D ratio reliably. And even if there were, it would likely be astronomically expensive.
Yeah I was thinking along those lines, but was wondering if anybody made tapered-to-cylindrical honing stones. I don’t even think ID grinding could do it very effectively, you’d have crazy L:D still.
 
This sounds like something to be done by tapering the end
of a long "superior type" two stone mandrel

Tennessee abrasives 800/346-6399
 
Material is 7000 series alu. It’s not blind, it’s a tube, but one end is thicker than the other, the taper/butting is a noncritical aspect that joins one tight tolerance larger diameter and one medium tolerance smaller diameter together. I had considered drawn and butted tubing and then just honing the cylindrical part, but that doesn’t lend itself to higher volumes/automation very easily.
If you are looking for high volume, I would be looking into dampening boring bars and run a stubbed up 3/4" carbide bar to finish the critical diam close to the face. Did you mention the OD of the part? Do you have a steady rest on your lathe? Some rubber on the OD while turning the ID may absorb some vibration as well.
 
If you are looking for high volume, I would be looking into dampening boring bars and run a stubbed up 3/4" carbide bar to finish the critical diam close to the face. Did you mention the OD of the part? Do you have a steady rest on your lathe? Some rubber on the OD while turning the ID may absorb some vibration as well.
A 3/4” carbide boring bar won’t cut 10” deep without crazy chatter, even a damped 3/4” won’t (we already have one). OD is about 1.400.
 








 
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