Lathe Tool Offsets - Tool Relationships?

[suntravel]

Lathe measurement tool with a probe is now working for all kinds of configurations, regardless where the probe position is.

You can mount it so the X travel will reach ID and OD tools, just make sure that the position is repeatable and mount the probe 90 deg to the spindle with a square tip so it will work in all 4 directions.

Uwe

[Chaz]

Yep. I was actually at the lathe earlier to see where I could fit a tool probe, even if it was off centre. The Emco has limited space however.

I looked at some of the renishaw 2nd hand arms with probe tips. They are all too large but could be modified, I'm sure.

There's actually a UK guy (I think) that has made some custom mounts for the Emco 120 (similar size) but he isnt responding about selling them etc.

[suntravel]

Yep. I was actually at the lathe earlier to see where I could fit a tool probe, even if it was off centre. The Emco has limited space however.

I looked at some of the renishaw 2nd hand arms with probe tips. They are all too large but could be modified, I'm sure.

There's actually a UK guy (I think) that has made some custom mounts for the Emco 120 (similar size) but he isnt responding about selling them etc.

Do not rely on others fixing your stuff, it is no rocket science to find the best spot for your probe

Uwe

[Chaz]

Yep. I was actually at the lathe earlier to see where I could fit a tool probe, even if it was off centre. The Emco has limited space however.

I looked at some of the renishaw 2nd hand arms with probe tips. They are all too large but could be modified, I'm sure.

There's actually a UK guy (I think) that has made some custom mounts for the Emco 120 (similar size) but he isnt responding about selling them etc.

Do not rely on others fixing your stuff, it is no rocket science to find the best spot for your probe

Uwe

I agree, just liked his solution and that it was similar to what I wanted to do. That said, cant afford the Renishaw kit he is using but can take some ideas on the setup.



He uses Centroid too, even better.

[Chaz]

Some of his other vids are actually better and show how the device attaches etc.





Any idea on why he would have what looks like a probe, being probed? Is that to find the centre of the bore perhaps?

[Muzzer]

Unless your fixed probe is deadly repeatable, you will need to do a skim/measure/calibrate cycle each time you add new tools, surely, in which case the position itself isn't critical as long as it doesn't move until you've finished touching your tools off. AFAIK, those Renishaw arms aim to avoid that by being extremely repeatable, which is why they cost so much.

Don't know why he has 2 probes there. Presumably when finally set up and working consistently, he won't need both.

[suntravel]

Even with a perfect probe, you will be off If you change from Alu to stainless, unless the lathe is extremely rigid

Uwe

[BGracia]

What Renishaw kit is that guy using for his Emco? I see it's the TS20. There seems to be a several interfaces for it.

[Muzzer]

Even with a perfect probe, you will be off If you change from Alu to stainless, unless the lathe is extremely rigid
Uwe

Interestingly, this recognises that tool deflection when taking a skim cut results in an error between offsets measured this way vs touch probes (with no tool load). This puts into perspective the real life accuracy of machine tools, particularly at the lighter end of the scale, something we know and love!

There's a very similar effect to be seen when it comes to backlash since it is also usually measured with unloaded touch probes, whereas with a cutting load applied, the springiness of the various machine elements (ballscrews, brackets, frame, toolholder, chuck etc) result in an additional and often significant offset. The backlash characteristic is actually a combination of an offset and a spring constant. Youtube warriors like to overlook this effect when boasting of their machine's supposed accuracy.

An easy way to get a feel for this spring constant is to lock the slideways and try to turn the ballscrews manually. Rather than the ballscrews being locked solid, they will appear to have torsional springiness opposing turning. If you can judge roughly what torque would need to be applied to make a skim cut, you can get a feel for how much lost movement (ie offset error) would result. By way of example, on a my Bridgeport mill, the Y axis has slightly more spring than the X axis due to the design of the yoke that carries the ballscrew nuts.

[Chaz]

Ive ordered a 2nd hand Renishaw setup for my lathe. Its too big but will try make it fit. I also dont have the interface hardware, so will see if it works as is. I have actually got a Renishaw M15 interface on a lathe but its outside and despite being covered, may have been damaged and I dont know if it came to me working but might remove it and see if it works.