Reverse threading with a screw on chuck.

[mickri]

On all of my chucks the threaded portion is slightly smaller in diameter then the jaw portion. There is a small lip. The drawbar threads into what I called a keeper that fits inside the bore of the chuck and seats against the lip on the inside of the chuck. The two different TPI's effectively locking the chuck to the spindle. I have two different drawbars for the spindle on my lathe. One is to hold 3C collets and the other is for an adapter that holds end mills. My lathe came with the milling attachment. I will have to make a keeper that fits on one of the drawbars.

In the thread I mentioned above I asked if the drawbar needed to have a left hand thread and the response was no. That the different TPI's were sufficient to lock the chuck to the spindle.

 

[ThinWoodsman]

se a drawbar through the spindle with different TPI than the spindle to hold a keeper (wrong terminology??) on the inside of the chuck.

That could work. even if the keeper is just a device like a spider with the bolts tightening against the ID of the chuck where it registers against the spindle. All it has to do is provide enough friction to keep the chuck from loosening due to its mass (the force from the cut itself probably being very light).

 

[markba633csi]

Using backgears, you would likely have a goodly amount of time to notice the chuck wobbling and getting ready to fall off.
It's mostly in the non-backgear modes that I would be concerned. Mostly.
-M

 

[Dabbler]

At 65 RPM it takes 3 seconds to unscrew the chuck. fast enough for a problem.

 

[DavidR8]

I'm late to the party here....what's the advantage to reverse threading? Is it because the runs away from the chuck?

 

[kvt]

I have seen a couple of ways to lock the chuck on. One was a split ring that clamped on the spindle behind the chuck on one that had room.
Another was like told above, where they drilled and taped the back plate and put the set screws in to hole it on. I have not had a chance to make the mods to do this yet.

 

[mickri]

Threading away from the chuck gives you more time to disengage the half nuts. Joe Pie has a video on it.

Most discussions that I have seen concern parting. Not threading. Parting with the blade upside down has less drama and I believe less force on the work. Parting with the blade upside down on the front side requires that the lathe be run in reverse. With the blade upside down the forces involved push the blade up and away from the work. With the blade right side up the forces push the blade down and into the work.

 

[tq60]

If you "slam seat" for lack of better term, the chuck usually will stay put with light cuts.

Slam seat is turning the chuck slowly until it stops, loosen it about 1/3 A turn then turn it as fast as you can and it slams to a stop on the register.

Takes a good effort to bust it loose but it is seated well.

Sent from my SAMSUNG-SM-G930A using Tapatalk

 

[Dabbler]

@DavidR8 - The reasons for reverse threading are described in Joe Pieczynski's video as pointed out by @mickri

You can find it here:

On a D1-X camlock lathe it's a no-brainer. On a screw-mount spindle, without a secondary restraint system, it's dangerous.

 

[DavidR8]

@DavidR8 - The reasons for reverse threading are described in Joe Pieczynski's video as pointed out by @mickri

You can find it here:

On a D1-X camlock lathe it's a no-brainer. On a screw-mount spindle, without a secondary restraint system, it's dangerous.

So far I've had no problem threading toward the chuck but I can see why this method would be advantageous.