Re: stuck chuck

What you say is fine, Ondrej, but it nonetheless puts a big shock into the (cast iron) gear teeth.  If they were steel and the same size, it might be a different matter (loosen and tighten the first motion shaft nut on a BMC mini gearbox by simultaneously engaging 1st and 4th gears.  That's official and the only way it can be done).  This time, I had got the chuck properly stuck, not just a bit of dirt in the threads.  Also, I have disabled reverse, as I feel it is particularly hazardous with screw on chucks, unless you ram them on very tight, thereby leading back to problem 1!

I'm still thanking my lucky stars that this thread about stuck chucks and an impact wrench came up at the same time as a rerun of the one about headstock shims.  It was putting the two together as a means of locking the spindle safely, then applying sufficient torque that enabled me to succeed.  It even avoids any chance of an overload on the disengageable connection between the bull gear and the spindle, as the bull gear is not in the torque path.

Sincerely, and with best wishes to all you stuck chucks out there.


On Thursday, 23 January 2020, 08:47:36 GMT, Ondrej Krejci via Groups.Io <okrejci@...> wrote:

South Bend Lathe Co. recommended that a piece of wood be used against a chuck jaw or a bolt firmed fastened to a face plate and the lathe spindle turned manually in reverse while in back gear reduction, but that was before lathes came with their own motors.
On the only lathe I ran professionally with a threaded spindle, decades ago, the chucks and face plates were always loosened by running the lathe spindle in reverse at the lowest speed using a hardwood block.
Any strange notions of using impact wrenches or torches would have resulted in an altercation with the owner and my seeking new employment in another field.

Good luck,


On Wednesday, January 22, 2020, 03:21:23 PM EST, eddie.draper@... via Groups.Io <eddie.draper@...> wrote:

Managed to get the stuck chuck off today.

Gripped an offcut of 1 1/4" Whitworth hexagon in the chuck.  Engaged the belt on the slowest non backgear speed, just to use the inertia to reduce shaft rotation.  Applied a 3/4" drive electric impact wrench via a socket.

30 secs later, nothing.

Removed a thin shim from both sides of the chuck end headstock bearing and clamped it up tight.  Applied both the impact wrench plus a long open ended spanner to the hexagon, and applied a 14lb hammer to the spanner.  It took a few blows, but it came off.  If the headstock spindle had still rotated, I was intending to similarly lock the other end bearing.

Note:  I had used ISO 1000 viscosity steam oil on the threads when assembling it.

Chuck run back on gently, headstock bearing shims refitted, and lathe used normally.



On Monday, 13 January 2020, 09:04:35 GMT, eddie.draper@... via Groups.Io <eddie.draper@...> wrote:

Me too!  Also, I note that the illustrated machine has V belt drive and there appeares to be a gap between the pulley and the gear.  Our 14.5" has flat belt and no gap.  Ideas anyone?  I have a rather seriously stuck chuck at present, as it started to unscrew when I switched off, so to prevent it going flying, I switched back on again rather hurriedly and it seated in place with a significant bang.

I would caution against using the front diaphragm of the headstock casing as a reaction point, as it is a rather thin casting.  Whatever you do, keep the forces acting dead in line through it and do not drive a wedge between it and the bull gear, or you may fracture it out.  The dog for the bull gear to mandrel connection on the 14.5" is on the outer end, and the only exposed part is a rather slender handle that I would hesitate to use for this.

Hoping to upgrade to a similar size machine with Camlock!


On Sunday, 12 January 2020, 19:14:49 GMT, Steven Schlegel <sc.schlegel@...> wrote:

Is the shaft square in that area, or do you get leverage off the pin? I am trying to figure out how it works.


From: <> on behalf of Chips <sakr4360@...>
Sent: Sunday, January 12, 2020 9:21:36 AM
To: <>
Subject: Re: [SouthBendLathe] stuck chuck
Newb here, first post.
Mine was stuck when I got it due to sitting for 20+ years and yes I broke a tooth on the back gear.
Make one of these from 1/4 thick plate then put it on the bull gear opposite side of the little push pin that engages the pulley. Then you can crank on the chuck.
You can thank me later.

Join to automatically receive all group messages.