Lathe rear parting tool

[mikey]

I'd rather not do flanges, but the plinth height is 4". That's a long hole. Was thinking of using a long M8 SHCS.

You could always countersink the hole for the head, right? Drill from the bottom then drill from the other side and countersink it so a shorter screw will work.

No height gauge. Did buy one, but returned it, since it did not match the photos. Pics showed a carbide scriber, I got a steel one. Sort of a bait and switch. Got a refund, but haven't found a replacement. Some day...

Could measure the height from the bottom up, with some 123 blocks, ground stock and shims on the cross-slide. Not sure how accurate that would be with tolerance stack up, but it should allow a measurement.

However you measure the height, get it dead on. I would just go buy a digital height gauge and be done with it. You will need it again someday.

I'll redraw the tool holder, assuming a 2.5" x 2" x 4" piece of 6061. (Have a chunk on my desk.) My drawing is parameterized so if I need to change a dimension, I just type it into the spreadsheet and whamo, the drawing is updated.

I use paper and pencil - rub, rub, draw - whamo, updated!

This tool is really simple. All good tools are really simple. The tool does not take much stress so it doesn't have to be huge; it just has to be solid. The ledge and a single locking bolt is sufficient to resist all cutting forces. The two slots work; they prevent cracking and allow the top ledge to lock down solidly, accurately and only requires snugging lightly with a hex wrench to lock the blade in place. The top ledge only moves a few thousandths of an inch so cracking is very unlikely. If it hasn't cracked in over 25 years then I would say it has proven itself.

Try not to overthink it. I've already taken out anything in the design that doesn't absolutely have to be there.

 

[WobblyHand]

You could always countersink the hole for the head, right? Drill from the bottom then drill from the other side and countersink it so a shorter screw will work.


However you measure the height, get it dead on. I would just go buy a digital height gauge and be done with it. You will need it again someday.


I use paper and pencil - rub, rub, draw - whamo, updated!

This tool is really simple. All good tools are really simple. The tool does not take much stress so it doesn't have to be huge; it just has to be solid. The ledge and a single locking bolt is sufficient to resist all cutting forces. The two slots work; they prevent cracking and allow the top ledge to lock down solidly, accurately and only requires snugging lightly with a hex wrench to lock the blade in place. The top ledge only moves a few thousandths of an inch so cracking is very unlikely. If it hasn't cracked in over 25 years then I would say it has proven itself.

Try not to overthink it. I've already taken out anything in the design that doesn't absolutely have to be there.

I have moved my new design into my thread in Projects. Not nice to continue to clutter up someone else's thread. Sorry @Pescadora don't want to take away from you accomplishments, or fill your thread with my dumb questions. Time for me to discuss (my issues) in my own project. https://www.hobby-machinist.com/thr...-parting-tool-for-a-g0752z-g0602-lathe.98539/

 

[Manual Mac]

I just jury-rigged a set-up from loose parts I had laying around.
i Can Not believe how much better parting from the rear works for me!
I’m not *******rting you. What a break thru, and I can run it much faster with a deeper cut, & no digging in, or stopping the spindle.
This table failed for the intended purpose I built it for.
But I use it all the time in my mill vise bolting engine parts or fixtures to it either flat or vertical for machining.
i only wish I had built it 2 inches longer for parting from rear, but it works great the way it is.
in fact it works so well I probably will leave as is, (if it works, don’t fix it, eh?)
Even Harvey told me how pleased he is.

As an update I went ahead & made some tooling for the rear parting tool, & added 2” to the table with the tooling.
i am using an old Williams 2020 5/8” cutoff holder turned upside down.
once again I can’t believe how good this set-up works
no more digging in, stopping the spindle, & I can use much higher RPM.
and the pucker factor is (almost) gone.
And (once again) this is a SB9, a larger lathe would have similar results I suspect, but proceed with caution.
Cheers

 

[mikey]

Very cool, Mac!

Try rear mounting your knurling tool back there. The increase in rigidity has a significant impact with that tool as well.

As your confidence in your parting tool grows, parting becomes a routine non-event. Grooving, thread reliefs become simple tasks and your efficiency improves ... all because you moved your tool back there. Who woulda thunk it?

 

[Manual Mac]

It even turns fine.
Sorry, I’ll stop, I’m veering way off topic.