[How-To] Running a threaded spindle in reverse?

[robsig]

I just acquired my first lathe (SouthBend heavy 10L) that has a threaded spindle to attach the chuck and other equipment. I have heard never to try using this lathe in reverse as this will unthread the chuck. Is there a safe way to use this machine in reverse?

 

[SLK001]

I have run and threaded things in reverse with the same lathe. Just limit your cuts to light cuts and you should be fine. About the only time you'll need to run in reverse is for left handed threads that you single point.

 

[robsig]

Great- thanks.

 

[WobblyHand]

You can also thread right hand threads away from the chuck. However, you need to either use a left hand tool, or turn your (normal) right hand tool upside down to do it. Internal threading, at least for me, is easier using a left hand tool and using reverse. Just take it easy with light cuts and you should be ok. Light cuts are less than 0.010", more like 0.005" and under.

 

[robsig]

Thank you!

 

[mickri]

I made what I call a chuck keeper for my lathe. Why that name? Because it will keep the chuck from unscrewing when running in reverse. It is a long bar that fits through the headstock. The chuck end just fits the inside of the chuck. The other end is threaded for a nut to hold it in place against the out board end of the spindle. As long as the threads are a different pitch from the threads on the spindle the nut can not unscrew because the different threads work against each other.

 

[WobblyHand]

I made what I call a chuck keeper for my lathe. Why that name? Because it will keep the chuck from unscrewing when running in reverse. It is a long bar that fits through the headstock. The chuck end just fits the inside of the chuck. The other end is threaded for a nut to hold it in place against the out board end of the spindle. As long as the threads are a different pitch from the threads on the spindle the nut can unscrew because the different threads work against each other.

View attachment 498186

That's a decent solution for folks that don't have a back plate retainer feature on their spindle. Very nice.

 

[682bear]

I made what I call a chuck keeper for my lathe. Why that name? Because it will keep the chuck from unscrewing when running in reverse. It is a long bar that fits through the headstock. The chuck end just fits the inside of the chuck. The other end is threaded for a nut to hold it in place against the out board end of the spindle. As long as the threads are a different pitch from the threads on the spindle the nut can unscrew because the different threads work against each other.

View attachment 498186

I've been meaning to make one of these... I'll get a 'round tuit' one of these days...



-Bear

 

[CJ5Dave]

I have the same question about a boring head for a milling machine. It has carbide brazed boring bars. Looks like to me to use the bars horizontal out the end hole it will have to run backwards. Will this screw the boring head off the arbor?

 

[robsig]

I made what I call a chuck keeper for my lathe. Why that name? Because it will keep the chuck from unscrewing when running in reverse. It is a long bar that fits through the headstock. The chuck end just fits the inside of the chuck. The other end is threaded for a nut to hold it in place against the out board end of the spindle. As long as the threads are a different pitch from the threads on the spindle the nut can unscrew because the different threads work against each other.

View attachment 498186

Doesn't this limit the length of stock you can put in your chuck, or am I misunderstanding (most likely!) what you've made here?