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4

Upside down and backwards threading with screw on chuck??

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Mark Stonich

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#1
shows a slick way to avoid threading toward a shoulder.

Apparently due to viewer feedback, he added this warning to his comments:

"To all my viewers. Please exercise caution and use good judgement when running a machine with a true screw on chuck. Excessive spindle load with the machine in reverse could potentially unscrew your chuck causing damage and personal injury. Refer to your operator or machine manual for safety suggestions."

My new Grizzly G0602 has a thread on chuck. There are a couple of clamps that should keep the chuck from coming off. But if it moves at all, the work would be ruined.

Any suggestions? Locktite? :)

I will make a reverse tumbler. And the threads I want to cut are 24 tpi x 1.375 OD in aluminum. Probably 7075.
 

Mach89

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#2
I learned this trick a while back. Works really well. An upside-down tool is also useful for turning bronze. It helps keep the chips from flying all over the place (and down your shirt). The chips just fall down in the chip tray for the most part. Less mess to clean up.

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Mark Stonich

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#3
Mach89,
Thanks for the endorsement of his method. Never thought to use it for turning. Due to the tall compound of the G0602 it can be hard to get the tip of some tools low enough with the Grizzly T10166 QCTP. This would solve that problem

Now if I can just figure out how to lock my chucks to the spindle.
 

savarin

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#4
what about placing a brass section in the clamp holes and tightening that down onto the spindle, being brass it shouldnt damage the spindle thread.
I have just cut 2 "O" ring internal grooves in an 80mm bore in reverse, I just screwed the chuck on very firmly and took care.
 

Mach89

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#5
Now if I can just figure out how to lock my chucks to the spindle.
This may not be the best idea, but you could cut a couple or the flats across the threads and use large set screws. Again, probably not the best idea cutting flats on the spindle threads, but it's a thought.

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Mark Stonich

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#6
savarin wrote;
"What about placing a brass section in the clamp holes and tightening that down onto the spindle, being brass it shouldnt damage the spindle thread."

Sounds good. Or better yet, leave the clamps and add 2 more holes for the brass slugs.
 

RJSakowski

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#8
You should have no trouble running the 602 in reverse. The design of the two clamps is to draw the chuck tight to the shoulder register as well as preventing rotation. In more than three years on my 602 I have never seen any loosening of the chuck. (other than the tinme
 

fitterman1

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#10
Ditto to what RJ said, assuming your lathe isn't modded with a variable speed drive means you're attempting to cut a thread at 150rpm (your lowest speed). Pretty hairy at the best of times. I suggest you use the method put forward in the video, its your safest option and considering you are cutting ally at a fine pitch, your depth of cut will also be small, potentially minimizing the chance of chuck rotation.
I have variable speed drive on my G0602 (ideally its now a G0752) and I'm able to dial my speed down to about 20rpm but I prefer around 40-60rpm because I get a better finish when screwcutting. I also have a built in brake which stops the chuck within a second and I've never noticed a movement in chuck orientation.
I made a spider once to fit the lathe, and I actually removed the chuck and work together from the spindle to check the thread on the other end of the spindle for fit a number of times. Upon reassembly no change in crosslide position was made to check for motion on first pass. I never had an issue that day.
I think your only issue should be work stickout. If short its ok, but if long you need to support the end and work around that.
As Mach89 mentions, an upside down tool is handy. I have a boring bar permanently set upside down in its toolholder for when boring deep holes, I run the spindle in normal direction and bore the opposite side of the bore. This way I can see what I'm doing without hanging over the lathe and upsetting something.
If machining brasses and bronzes I make a chip deflector out of some brass shim and fit it to the tool clamping bolt closest to the working end and form it to sit above where the action is.
This saves me spraying the surrounding area and myself with swarf.
 
Last edited:

John TV

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#11
Thanks for the great responses. Didn't expect to get so many ideas, now I need to play a bit and see what works. This site is such a great resource.

John


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pdentrem

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#12
If you are not threading to a shoulder then just set the tool upside down, cut on the back of the bore hole with the chuck rotation in forward. If threading to a shoulder then threading in reverse as shown will work just be careful as already stated.
Pierre
 

Splat

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#13
Instead of retyping it check what I wrote in this thread. Cheers.
 
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