Broken threads on the QCTP of my compound slide

[better-lathe-than-never]

I have a 9x20in Jet BD-920N mini lathe. I installed an AXA Tool holder with the M8 tool post that I drilled and tapped myself. Apparently I did a sloppy job in that and now I can't tighten the tool post in place making it impossible to run the lathe. I'll post photos of my compound slide, but it's a standard on onthe 9x20 Jet lathe.

Is there a way to make this more ridgid or do I have to purchase a new compound slide body?

 

[homebrewed]

I ran into something like that with my mini lathe. It turns out that the screw hole used to attach the tool holder is drilled/tapped all the way through. If you use a screw that's too long it will go all the way through the compound and fetch up against the cross slide, locking the compound in place. Maybe that's what you are encountering?

 

[better-lathe-than-never]

I ran into something like that with my mini lathe. It turns out that the screw hole used to attach the tool holder is drilled/tapped all the way through. If you use a screw that's too long it will go all the way through the compound and fetch up against the cross slide, locking the compound in place. Maybe that's what you are encountering?

You know... it's possible - it doesn't seem to find bottom and snug up as it should. I'll see if I can bottom it out and try to get it snug against the cross slide.

 

[Cadillac]

If the thread is stripped it looks like the thread on your post is necked down. Make a new post with a larger thread. Retap compound and make sure your not to long.
I have the same lathe and the compound has been replaced with a solid tool post riser. Makes machine ALOT more rigid.

 

[homebrewed]

You know... it's possible - it doesn't seem to find bottom and snug up as it should. I'll see if I can bottom it out and try to get it snug against the cross slide.

Be careful, you don't want to damage the top of your cross slide. A quick way to determine if that's what is going on: install the screw without the QCTP and measure how much sticks out when it (lightly) hits bottom.

 

[better-lathe-than-never]

After closely examining the part, I am now certain that the thread in the top slide tool rest is stripped/broken. Others here were recommending I make a new stud, etc - I don't have a functioning lathe so how can I do that... I'm thinking about just drilling/tapping a hole from the back through the top of the slide and through the tool post itself to immobilize it.

 

[Cadillac]

Will a off the shelf bolt get you locked. Then make new stud then retap. My thought and I could be wrong is you would be taking away strength in the wrong area. And not fully solving the problem, the shaft will not be secure enough. Tool post will move!
Rethreading is gonna fix it the right way to get you a solid of a connection as it’ll allow.

 

[better-lathe-than-never]

Will a off the shelf bolt get you locked. Then make new stud then retap. My thought and I could be wrong is you would be taking away strength in the wrong area. And not fully solving the problem, the shaft will not be secure enough. Tool post will move!
Rethreading is gonna fix it the right way to get you a solid of a connection as it’ll allow.

I don't follow what you're saying: I cannot use my current lathe - the tool will not hold fast, so I cant make anything with it.

UPDATE: Oh I guess you're saying: find a 9/16'' bolt to temporarily immobilize the tool-post and make a bigger stud... that won't work because it's the thread in the cast iron body that's bad, not the stud.

Would welding that cast iron to that steel stud be an option (at least temporary)? Just to immobilize that tool post under that top slide? I don't know how cast iron would react when welding -

I really screwed myself, because I am unable to find a replacement compound slide body - I thought LMS had the replacement part, but they told me it won't fit... sent email to Grizzly - waiting. If I can't find a replacement (Plan B) then I have to be very careful with that brick that I've got.

 

[stupoty]

After closely examining the part, I am now certain that the thread in the top slide tool rest is stripped/broken. Others here were recommending I make a new stud, etc - I don't have a functioning lathe so how can I do that... I'm thinking about just drilling/tapping a hole from the back through the top of the slide and through the tool post itself to immobilize it.

Re tap the hole to bigger thread, use a bolt or threaded rod and make a temporary tool clamp from flat piece of steel and some packing blocks (can't remember the name of this style of tool mount , was very common on old UK lathes) or refit the four way tool holder.

Stu

edit - example of a clamp style tool holder on a small lathe,

Grayson Lathes

Small English lathes by a London Compnay, Gray & Son. Re-badged Randa lathes

www.lathes.co.uk

 

[ttabbal]

If you have a mill, it would help make sure you drill/tap straight. Or a drill press? I would remove the top of the compound to do the job so you don't get chips in the sliding surfaces. My compound (PM1127) came with an M10 hold down. I wouldn't want to go smaller than that. I made a new stud as well, that has a wider section in the middle. So it can tighten against the compound top to ensure everything is good before installing the QCTP. For now, just use a bolt or bit of all-thread to hold the QCTP so you can make a new stud or whatever as needed.