Lathe tool height

K

kmanuele

H-M Supporter - Diamond Member
H-M Lifetime Diamond Member
Joined
Jan 25, 2022
Messages
110
Agree this is probably splitting hairs but an idle mind rattling around:

Say I have a RH HSS turning tool with a side rake (say, 12 degrees), minimal back rake.

A nose radius of 1/32" so the tip of the tool is slightly lower than the leading edge.

Then where the tool engages the work relative to work centerline will depend on the DOC. Where should I set my tool height - to the leading edge?

More generally, is it better to err lower or higher when setting tool height?

Thanks
 
I have often wondered about this too. Looking forward to the responses from the people who know what they are doing.
 
I made the Jo Pi height gauge years ago. Set the point to be exactly at height by scrapping a blade across it. I almost never see a nub on a facing cut. Where this comes into play is after you do a touch up on a HSS bit. It will still cut OK for most applications. Then when you do your facing cut, the nub shows up. Just bring it up a half thousand or so at a time till it disappears and you will be on the money.

Where the height gauge is good is that you can change tool bits in the middle of operations and get them set right. You don't need to do a facing cut or match the tip to the tail stock or head stock point.

Reading your post, when I touch up a radius, it is the highest point. If it is lower then you are cutting with negative rake. Pretty much, all of our cutting is done with positive rake. Takes less power. Look at the pictures of HSS tools. They show the front, side and top angles. The point (radius) should be up, not down or flat.
 
again, give me a lot bigger break; half or a quarter thou is less than measurable on tool height; this is a seat of the pants thing!
 
I have found that when parting on a smallish lathe that setting the tool height .003 below the centre line reduces chatter a lot.
 
You must log in or register to reply here.
Back
Top