Lathes and reverse

[God mode restorations]

Evening guys .
A random question this one.
Most old and new lathes have a reverse.
As stupid as this might sound but in reverse what prevents the chuck from unscrewing it's self.

 

[zx9]

With our lathes nothing, that is why they have locking chucks on bigger lathes.

 

[Seadog]

Nothing Spencer. However, if you're not stupid and try to take large cuts in reverse or decelerate the spindle too quickly, you shouldn't have any problems. This does assume that the threads are in good condition though.
I've just posted about this on the Boxford group where someone has modified the rear of the backplate to mount a locking collar.

 

[God mode restorations]

With our lathes nothing, that is why they have locking chucks on bigger lathes.

I no they have the cam lock on bigger machinery. But it just randomly popped in my head

 

[God mode restorations]

Nothing Spencer. However, if you're not stupid and try to take large cuts in reverse or decelerate the spindle too quickly, you shouldn't have any problems. This does assume that the threads are in good condition though.
I've just posted about this on the Boxford group where someone has modified the rear of the backplate to mount a locking collar.View attachment 134565 View attachment 134566 View attachment 134567 View attachment 134568 View attachment 134569

That's a good idea

 

[optima21]

even the tiny hobbymats have the chucks screwed to the spindle nose.

when I got my 4 jaw chuck many years ago I had to skim the recess for the backplate, so that I could use the 4 jaw and 3 jaw chucks on the same faceplate

and machining a new backplate for the chucks

 

[hareng]

Very very rare my old scrapped ML7 unscrewed it was a bitch to get off a few times a day.
As log as the cutting force is less than the tightening force your fine.

L0, L00 and D the standard the last 60 years far superior.

 

[Bill Edwards]

My view is only use the reverse to wind the carriage back for threading with the nuts engaged, no cutting forces, ever. Not worth it to me.

 

[Richard.]

Another stupid question. Why would you take a cut with the chuck rotation in reverse?
I can see the need for traveling in the other direction towards the tail stock but then you just use a tumble reverse gear in which case the chuck still spins the forwards way. Is that right?

 

[Seadog]

Why would you take a cut with the chuck rotation in reverse?

Cutting a right-handed thread in a blind hole?

 

[Richard.]

Cutting a right-handed thread in a blind hole?

I see. Do you mean a left hand thread. Right hand I cut with the lathe in forward direction

 

[optima21]

I was thinking about running in reverse a few weeks ago for boring a hole as I would be able to see the tip of the tool easier

 

[Richard.]

I see. Do you mean a left hand thread. Right hand I cut with the lathe in forward direction

Ignore that. Daft moment of stupidity.
I know what you mean now. Engaging the cut away from you

 

[Seadog]

If you need to cut a thread in a blind hole you need to cut in reverse. Consider threading on the lathe using a tap. The tap is run into the workpiece, it is cutting on the forward stroke, if I can use that analogy. Now, if you're thread cutting on the back stroke the lathe needs to be running in reverse, with the tool inverted.

 

[Richard.]

I see so you wouldn’t use a tumble reverse gear to drive the lead screw forward you would start in the hole and cut out.
The whole lathe running in reverse

 

[Bill Edwards]

Another stupid question. Why would you take a cut with the chuck rotation in reverse?
I can see the need for traveling in the other direction towards the tail stock but then you just use a tumble reverse gear in which case the chuck still spins the forwards way. Is that right?

You can cut a regular external RH thread starting at the shoulder working out, eliminating any worries about stopping at the right time. Tool inverted of course, and able to run the machine faster.

Some people bore with LH boring bars in reverse so they can see the cutting action better.

If something such as a parting tool is unable to drop low enough to be on centre height it can be flipped and run in reverse.

Perhaps nothing that’s usually essential, but nice to have - I like the idea of reversed thread cutting quite a bit.

 

[Pete.]

Cutting a right-handed thread in a blind hole?

Yep. Also cutting metric threads on an inch screw, and vice versa. I also use it for putting chamfers sometimes if I'm chamfering the ID and/or OD of something to avoid turning the chamfering tool around in the holder or swapping tools. Also sometimes to face something wide and thin I use reverse and face on the other side if I'm trying to combat ringing in the part. Also sometimes to true a thin disc held lightly in the jaws if I'm feeling particularly bodgy.

Oh yeah - and for winding coils of copper wire to make a 'battery train' for my school teacher daughter to use in her lesson on magnetism.

https://www.dropbox.com/s/j6w94041m6utv1w/battery train.mp4?dl=0

Lots of reasons.

 

[Richard.]

Yep. Also cutting metric threads on an inch screw, and vice versa. I also use it for putting chamfers sometimes if I'm chamfering the ID and/or OD of something to avoid turning the chamfering tool around in the holder or swapping tools. Also sometimes to face something wide and thin I use reverse and face on the other side if I'm trying to combat ringing in the part. Also sometimes to true a thin disc held lightly in the jaws if I'm feeling particularly bodgy.

Oh yeah - and for winding coils of copper wire to make a 'battery train' for my school teacher daughter to use in her lesson on magnetism.

https://www.dropbox.com/s/j6w94041m6utv1w/battery train.mp4?dl=0

Lots of reasons.

Cheers Pete.
Some nice info and examples.
I’ll be honest it’s never crossed my mind to turn the chuck in reverse. I’ve worked away from the chuck toward the tail stock many times but that’s it.

 

[Maker]

I sometimes put my lathe in reverse but I can't remember why now. It's a camlock spindle though so it doesn't matter.

 

[Seadog]

Decelerating the spindle quickly from reverse will tighten the thread...

It will. My

Decelerating the spindle quickly from reverse will tighten the thread...

It will if you're in reverse. However, in forward you could unscrew it.