Lathe Parting Tool Spring Type Tool Holder For QCTP

[C-Bag]

I had never bumped into this and did a search because you said JR you'd seen it else where. Looking at it I had an inkling, but I wanted to make sure. What an interesting fix. Just out of curiosity did you try it without the spring pin, just the hole? For whatever reason I can't get that it really does add "spring".

My lathe does indeed put up a chatter when trying to part off. Soon as I can figure out where I can get a chunk of steel like that this is going on the must make pile.

Thanks for the plans, parts list and pix, good job.

[jjr2001]

Hi C-Bag, I have seen similar types on eBay usually under the brand Williams, Atlas, or Armstrong.
They are from the old days when lantern tool post ruled. Tom Lipton of Oxtools has one he made
years ago and explained it like this. The pivot point is above the tool bit so the torquing force tends
to move the tool bit, when under extreme load, away from the work instead of into the work like
a normal tool setup.

In my testing I did use it without the roll pin and it was just too free and the tool bit seemed
to jump around. The parting tool I was using chattered a lot when I used it in a standard
tool holder but when I used it in the spring holder with the roll pin the chatter was gone.
I could feed in and curl off chips quite well on the 2" blank I was testing it on. I have seen
versions of this tool without the roll pin.

I suppose tool rigidity depend on the steel used. I just had a piece of hot rolled and
found that the pin does make it work better. I could see an entire build of several of these trying out
different diameter holes starting with say 1/4" and working up to find a sweet spot for the particular
setup and lathe in use. The other thing in my version is the long "key" that can be adjusted in or out
for different extensions toward the work being turned. This gives some latitude in setup and the
ability to "tune" the tool in case harmonics start to give a problem. However the main reason for the long
"key" is so the tool can be set flush with the forward face of the QCTP.

Ah, so many tools to build and so little time!

Cheers, JR

[jimfols]

Thank you JR,
I have been wanting one of these and this is it.
Jim