Curiosity question - compound rest angle

[mxtras]

- A curiosity question here -

What angle do you typically run your compound rest on your manual lathes? I know it changes frequently but what's 'home' for you? Is there anyone that uses anything other than 45 for their base setting?



Scott

[Karl_T]

Mine is normally set at 30 - ready for threading. I also run the compound all the way back against the stop, more rigid. I seldom use the compound anyway.

Karl

[HuFlungDung]

Mine is normally set at 90 - ready for threading.

A word of explanation: our lathes have a DRO on the X axis (that's the cross slide). So to preserve accurate position of all the tools, it is generally forbidden in our shop, that the compound be turned to any other angle, and if it is, it has to be immediately trammed back to 'square', as soon as possible. Our larger lathes all use the same style of multi-fix toolposts and all the tools are shared from one large pool. This permits usage of a standard set of offsets for all the tools on any lathe.

I used to use the compound set at 29° to the X, but found that carbide threading tools really did not last that well unless both edges are kept cutting. That is, the dragging of the right side of the tool down the flank of the thread did not enhance insert life. It actually worked better to just plunge at 90.

That being said, for a coarse thread, we might throw a TNMG (60 degree triangular insert) tool on the machine and rip a few passes before switching to a proper thread tool. Or, we will jog the compound back and forth a few thousandths on alternate passes as the tool works its way down to full depth. We keep both edges cutting most of the time. Threads are not 'tenderly cut' in our shop, until the last finish cuts, because that is all that counts

On our small 15" Clausing, we do swivel the compound, but more because of an interference problem between the compound (if set at 90°) and the tailstock.

[BobWarfield]

It either sits at 45 or 90, depending on whatever I last did.

Not clear once I get it CNC'd what will make the most sense. Hu's explanation sounds right to me though.

Best,

BW