Locking Threaded Chucks

[DavidR8]

Thought I'd revive this topic based on some chatter on @YYCHM's threading tool thread (see what I did there?)
The perennial question of how to reverse thread on a lathe with a screw-on chuck.
There's this example

Southbend 9C Lathe For Sale

Why so little? I am almost thinking of shipping it to AB and flipping it for $1650. Tom, I have to say because I’ve noticed a common trend with you. It probably won’t go over well being a new member but I can’t imagine this sits well with others. You want to take a deal being passed on to...

canadianhobbymetalworkers.com

 

[DavidR8]

Model Engineer

www.model-engineer.co.uk

 

[DavidR8]

https://img.photobucket.com/albums/v227/brnstn/Weiler/Weilerchucktightener001.jpg

 

[YYCHM]

Model Engineer

www.model-engineer.co.uk

View attachment 20127

Can't picture how that accomplishes anything?

 

[DavidR8]

Can't picture how that accomplishes anything?

I agree, there needs to be some sort of relief cuts in the stub to allow the collar to tighten on the spindle nose.

 

[DavidR8]

A big thread on Hobbymachinist.com

Locking on a threaded chuck ?

Howdy Guys....and Gals if your out there ! ... I have been contemplating the threaded chuck coming off when using reverse on the motor problem..... ..... I would imagine a simple screw into the side of the chuck adaptor would cure this problem.... but I've never read where anyone has tried...

www.hobby-machinist.com

 

[Darren]

I had a threaded spindle on my V10p. Emco uses a locking collar with 4 relief cuts. It works great, when you remember to tighten the collar.

 

[YYCHM]

I had a threaded spindle on my V10p. Emco uses a locking collar with 4 relief cuts. It works great, when you remember to tighten the collar.

Got a pic?

 

[Darren]

Got a pic?

Locking on a threaded chuck ?

Locking the chuck to the spindle has been discussed before. Here's one such thread....... In this reply Bob (@RJSakowski ) shows how his spindle has a groove to lock the chuck on: https://www.hobby-machinist.com/threads/thread-crest-override.40895/post-351007 here, I suggested a draw bar type...

www.hobby-machinist.com

 

[Thomas]

 

[Darren]

So i had a chuck spin off on me once.

I was asked to do a quick job. Shop wasn't heated, was pretty cold, but it was a quick face off to thickness job on a round spacer of some sort. I had to change chucks and neglected to fully tighten the lock ring. When i turned the lathe off at 2000ish rpm, due to the cold and thick headstock oil im guessing, the 5" chuck left the spindle, dropped onto the lathe bed...and flew right at me. It hit me in the chest, grabbed my sweatshirt, hit my hand as i blocked it, climbed up my sweater, and whacked me in the chin. I caught it before it hit the ground, and then i almost hit the ground. Lathe bed was missing a chunk,, palm of right hand missing a chunk, and the chuck was damaged beyond repair. Chest hurt like i'd been hit by a truck, palm should have had some stitches. I'll never own another threaded spindle again. Be careful if you have one.

 

[Tomc938]

That must have been a terrifying moment - once you had a chance to figure out what actually happened.

 

[Darren]

That must have been a terrifying moment - once you had a chance to figure out what actually happened.

It was. It happened very very quickly.

But more than that i felt like an idiot. I know i tightened the clamp, but obviously not enough. I don't even like telling anyone about it, but i think its an important reminder.

 

[Tomc938]

I can relate. I will never mention to anyone the times I have left the chuck key in the chuck...depending on RPM, can be a gentle reminder or a hypersonic missile.

 

[YYCHM]

My reverse lockout mechanism....LOL

I did this after watching my chuck unscrew itself one time.... luckily I caught it in time. I think I was trying to reverse out a stalled drill bit.

The chuck key thing..... well... you probably only do that twice before smartening up.

 

[Darren]

I definetly didn't hit reverse....wasn't possible on that machine, but thats still a good safety measure.

 

[Dabbler]

The brits are famous for their improvised anti-unscrew hacks for their myford screw-on chucks. Apparently they can indeed safely lock a chuck on. (no endorsement here, though)

@dfloen that was a very close call.

 

[Johnwa]

I had a threaded spindle on my V10p. Emco uses a locking collar with 4 relief cuts. It works great, when you remember to tighten the collar.

The chuck @YYCHM has is an Emco chuck. The clamping backplate was likely OEM. There are plenty of images of them on the web.

 

[YYCHM]

Has anyone seen the Emco clamping backplate applied to a 3J? A 4J you have to dial in anyway you look at it.

 

[Darren]

I had it on the factory 3 and 4 jaw chucks, and one that I made for my 5" Bison set true. The clamp did not change the runout at all.