G0752Z spun the quill :(

[WobblyHand]

So just drilling out a piece of 12L14 with a 3/8" drill. Was going to make a boring bar bushing. Thought I'd put a 3/8" hole through, then put the tube in the boring bar holder to accurately line it up with the spindle. Then drill to "size" and ream. That was the plan anyways.

Seemed a little harder than usual to advance the quill. Was clearing chips every so often. Near the end of the hole, (at 2" extension) all of a sudden, the drill chuck, quill and handle started rotating as one assembly! Took a moment to process this and decide this wasn't good. More like a moment of astonishment, then realized I had to do something. Stopped the lathe. Loosened the drill chuck and backed off the tailstock. Handle is stiff to move - doesn't want to move. Removed the tailstock and put it on the bench. Using an old drill chuck, extracted the drill from the workpiece. It wasn't hard to remove.

From the parts breakdown, I think if I take off the handle, I might be able to drive out the leadscrew and quill from the handle side out the quill side. Not looking forward to viewing the carnage. Maybe the set screw pin sheared under load. Anyone have tips for disassembly? Gee, was having fun in the shop, until that bit of excitement!

 

[mmcmdl]

Quill come off the leadscrew and sheared the pin ?

 

[Navy Chief]

It sounds like it either sheared off the setscrew or the setscrew was too short and it jumped /wedged against it. Either way it is probably tight due to what is left of the setscrew not being in the groove and it wedging against the quill.

Sent from my Pixel 5 using Tapatalk

 

[WobblyHand]

Quill come off the leadscrew ?

No. Or at least I don't think so. Stuck at 2" extension, rotated about 180 degrees from where it should be.

Edit: Numbers are on bottom of quill now.

 

[WobblyHand]

The set screw will turn outwards, I will remove it. I had hoped backing it off some might help, but so far it hasn't.

 

[mmcmdl]

I assume this was on the backplate project .

 

[WobblyHand]

I assume this was on the backplate project .

Of course. It was me making a 1/2" bushing so I could hold my 1/2" carbide boring bar, in an AXA-4 holder, (3/4" hole) so I could work on the back plate. Oh well, I'll fix the tailstock somehow. Minor bump in the road, in the scheme of things. Stinks though. Guess I will have to drive it out. My drill chuck is still attached to the taper, so I don't want to drive the assembly out onto the floor!

 

[mmcmdl]

If I find one , I'll throw it in the box . Incoming pic on your other thread . It's always something !

 

[RJSakowski]

The G0602/G0752 uses a rather feeble means of preventing quill rotation. A single set screw atop the tailstock rides in the keyway so that, in essence, a single thread is making contact and at a single point at that.

I buggered up my keyway when I was using excessive torque. The symptom was that the quill was hard to move. I managed to free the quill and extract it from the tailstock. It had a raised burr where the quill had tried to rotate. Stoning the burr eliminated the hard travel symptom.

To fix the root cause of the problem, I made a special dog point set screw. The dog point of the set screw was an unthreaded portion of an 8mm set screw followed by a short thread and capped with a slot for turning. The set screw had to be inserted from inside the quill socket which was a bit tricky but I managed to position the set screw so that I could pick up the slot with a screw driver and thread it up into the tailstock. The dog point now presents a much larger surface to the keyway, preve4nting the future raising of a burr.

An alternative is to re-thread the tailstock to 10mm and use a conventional dog point set screw. In any case, a jam nut should be used to prevent the set screw from riding in or out during use.

 

[Navy Chief]

The G0602/G0752 uses a rather feeble means of preventing quill rotation. A single set screw atop the tailstock rides in the keyway so that, in essence, a single thread is making contact and at a single point at that.

I buggered up my keyway when I was using excessive torque. The symptom was that the quill was hard to move. I managed to free the quill and extract it from the tailstock. It had a raised burr where the quill had tried to rotate. Stoning the burr eliminated the hard travel symptom.

To fix the root cause of the problem, I made a special dog point set screw. The dog point of the set screw was an unthreaded portion of an 8mm set screw followed by a short thread and capped with a slot for turning. The set screw had to be inserted from inside the quill socket which was a bit tricky but I managed to position the set screw so that I could pick up the slot with a screw driver and thread it up into the tailstock. The dog point now presents a much larger surface to the keyway, preve4nting the future raising of a burr.

An alternative is to re-thread the tailstock to 10mm and use a conventional dog point set screw. In any case, a jam nut should be used to prevent the set screw from riding in or out during use.

Sounds your custom set screw is a good solution to the problem.