[wrechin2]

I am boring out cylinders on a outboard block. Have no problem centering and all that. My question is what RPM's can I run my boring head at??? I am running at 270 rpm with a .003 feed rate. finish is good plus I have to hone to finish. Problem is it is SLOW GO! What rpm should I run this head at? I have enclosed a pic of the boring bar I have, not actual but the same. R-8 spindle on a bridgeport machine with the off set tool. Thanks to all who reply!!!

[roysol]

Given the P.O.S. criterion style boring head with a large offset boring bar (held on by one screw:nono, and an r8 interface and likely not the tightest spindle bearings (quill, if you prefer), I think you've done well.

You said "cylinders", plural. If you actually have some production quantity to do, I would be looking at a different machine and tooling. The imbalance of that boring head alone will severly limit your rpm. Feed rate is a function of rigidity and tool nose radius. You can feed faster with a larger radius, but the increased contact area may cause chatter.

Cheers!

Roy Solomon

[wrechin2]

no chatter what so ever. Roundness is under .0005. I was impressed, just very slow process. End result is good. I sped up to 650 rpms at .0015 feed rate and it was ok. Alot faster and still good finish. Thanks for the info!!!