Boring a super smooth surface

Ned Simmons wrote in news: snipped-for-privacy@news.suscom-maine.net:

True, but not the same grade/material.

On a related subject I was making a cross slide stop for my Southbend lathe

A buddy, and my maching guru came by later that day for a rum and coke session. I dragged him down to the shop to show off my latest triumph. As soon as I said "no shake" he got that "total BS" look in his eye and grabbed the protuding shaft. Try as he might he could not detect *any* play! This guy had forgotten more about machining than I will *ever* learn. Essentially, I guess, I sort of 'burnished' that hole.

Regards. Ken.

See McMaster page 3394, exactly the same grade and material - Grade 25,

Ned Simmons

Thanks for the tip

I can visualize you forcing the bearings into the hole and the outer race of the bearings picking up the same RPM from the hole as the two meet. So the relative positions of the bearing race and the hole remain constant throughout the push and withdrawal. Now, if my understanding of what you are doing is correct, then is there any particular advantage drawn from having the chuck rotating? The operation appears not unlike swaging a barrel.

The impression that I got was that the OD of the bearing was smaller than the ID of the bore, so it rolled around the bore as the workpiece rotated. (The "some pressure" would be pressure of the roller against the side wall of the bore, not axial pressure. Thus, it became a form of roller burnishing tool. Not as stiff as one with three rollers pressing into the bore at 120 degree spacing, but for a soft workpiece material, it should suffice.

Enjoy, DoN.

That makes sense. Good call. I was thinking more of a swaging operation but I can see I was wrong.

Ned Simmons wrote in news: snipped-for-privacy@news.suscom-maine.net:

I stand corrected. I did a quick search and found the ones on page 3404. You would think that there would be more of a price difference between the two. I guess since 52100 is used for bearings, the quantities they are made in offsets the price for the extra precision.

I haven't visited the newsgroup in quite a while, and you have probably already finished your project but here is how I would do it.

I would use the same basic procedures that are used in making a custom rifle barrel. First drill the hole undersize, ream and polish for a good finish leaving the hole slightly undersize. Then silver solder a button (ball bearing) to the end of a rod that is smaller than the hole size. Using a good high pressure lubricant such a moly powder, or even anti-seize compound that contains a fair amount of copper I would push/pull the button through the barrel. Doing this with the hole about 0.005" undersize to start with should leave a good finish.

Clean the inside to remove the moly or copper with a good penetrating oil (such as Kroil) and very mild soft abrasive such as "J-B Bore Compound". This is what is used by some shooters to clean the moly and brass from their rifle barrels, without causing any extra wear. The J-B is a soft vegetable based abrasive and will not remove any steel.

And it seemed to me that the bearing was oversized by some amount for the hole, and it was a sort of dynamic ball burnishing effect.

I would be interested to know the details of the operation because it sounds like it works pretty well.

Jim

Thanks, project still in progress....it seems that alot of these methods require making things a "normal" size...I gueass that's the key. If you wander out of "normal" you enter tha land of cutom tooling (cutum reamers....yikes).

Thanks for the info...

John

Thanks Ned for the tip!