A tool post test

Seeing Dave's efforts at making some more QCTP holders (https://www.woodworkforums.com/f65/ma...6/)has worn me out just looking at it, but has made me wonder whether any particular style is better than another.
Is anyone interested in testing the repeatablity of their holders for a comparison? So far I've thought of 3 tests that might be meaningful -

• Locking a holder onto the post and checking the vertical position
• Locking a holder onto the post and checking the horizontal position
• Locking a holder onto the post and checking the vertical deflection while applying a small torque - say 20Nm

The results would mainly benefit people thinking about converting to a QCTP set up and give them a starting point - are clones more rigid than genuine; are home made holders as good as factory; is there a brand of clone better than another; is a used holder much worse than new?
I was thinking of doing this say 30 times and comparing the results - average and standard deviation. My holder is a secondhand Aloris so I could do that but if other members have other types or styles (including the various clones) then we could get a meaningful set of comparative data.
The first two tests are simple but the third needs some thought as if we are not careful things could be influenced by the rigidity of the compound & cross slide. I'm thinking that the torque would be applied by welding a bolt or nut on the side of a piece of bar and securing that in the holder, with the measuring device (dial indicator) at a set distance from the torquing point.
I'd post a test plan so we are all doing the same thing but first we need to agree what that is. Anyone got any ideas on whether or not these tests will tell us anything? Is there a particular method we should adopt? Are there other tests that should be done at the same time? Most importantly, does anyone want to do any of this?

Michael

I think Ray and Josh would be able to do the Dickson style better than I ever could with all that measuring gear they have. If they don't have time I will do it.

Dave

Quote:

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Originally Posted by Dave J

I think Ray and Josh would be able to do the Dickson style better than I ever could with all that measuring gear they have. If they don't have time I will do it.

Dave

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Hi Dave,

No problem, I will have a look later to see what measurements would work.

Regards
Ray

I just had a look at my QCTP and subjected it to a very rudimentary repeatability test. I ran the indicator stylus across the top of the cutting tool. About 0.0005" variation over a number of mountings. I have noticed that subjecting an indicator spindle to side load invariably leads to discrepancies. Some Swiss chinglese :) -

To avoid different measures of the workpiece,
when changing the tool, the cutting edge always
to be returned to the same position, relative to
the workpiece. We guarantee an accuracy of
0.01mm after a change with the Böni quickchange
tool holder.

Close enough to my crude findings.

Applying a load on the rear extended portion of the cutting too resulted in no needle deflection.

My findings are unscientific and I dare say pretty irrelevant to you blokes with Hare and Forbes tool posts. I would be interested to hear how the Boeni shapes up when compared to a Tripan or a Multifix. Or a Dickson or Italian Rapid.

Bob.

Thats a Dickson style Bob.

Dave

Quote:

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Originally Posted by Dave J

Thats a Dickson style Bob.

Dave

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Sure is Dave :U

https://www.woodworkforums.com/f65/di...2/#post1408138

Never did find out if any other holders fit the thing.

Michael I think it's a great concept and I'd definitely be interested in the findings. However I'd suggest all will repeat etc extremely well and the variations between them minimal. It basically came down to who got to patent one design before another company.

Nevertheless there will be differences, but because they're so small the only way I could see meaningful data coming from the exercise would be if one person on one lathe was repeating the tests using the same test equipment and protocols.

Pete

Quote:

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Originally Posted by Anorak Bob

Sure is Dave :U

https://www.woodworkforums.com/f65/di...2/#post1408138

Never did find out if any other holders fit the thing.

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I must have been absent that week, LOL

From memory mine where 70mm center of V to center of V, made things easier.
My original holders where slotted then V'ed, this would be to do with manufacturing because the tops of the V's on the tool post are machined off so they would never come in contact with the base of the V on the tool holder anyway. I just wish my model came 3 sided instead of 2, the next size up does.

Dave

Dave

A rough test on the H&F Dickson clone.

Repeatability ( measured vertically relative to the cross slide ) seems to be better than 0.03mm 90 % of the time +-0.01mm
Stability ( measured vertically relative to the cross slide ) pressing down by hand on the cutting side ( with a 20mm boring bar, just happened to be what was already there) no deflection on a 0.01 dial gauge.

No sure if that helps anyone or not.. I don't have access to Aloris, Boeni, Tripan, Multifix, or Italian Rapid :)

The rigidity of the toolpost is of course a critical factor on any lathe, but I suspect that for low horsepower manual lathes like we are talking about, there is probably no much difference between the different QCTP designs.

For a 25Kw high speed CNC monster, it might be a different matter altogether.


Regards
Ray

Thanks Ray, I agree for the home shop that is plenty good enough. You could set a tool slightly low or high in one and put it out more than that.

Dave