Performance CCL tailstock lock

[ThornOfCamorr]

Good morning,
I finally managed to get a closer look at an Axminster Performance CCL I bought used a couple of weeks back. While trying it out, i noticed that the tailstock quill was rotating.

The quill has a groove which should stop it from turning. But the barrel itself does not have anything which locks into that groove (apologies, not sure how to describe it better). The tailstock lock is simply a screw. So nothing is engaging with this groove. Tightening the tailstock lock just means the screw presses against the quill, stopping it from rotating but it also won't slide in the barrel any more.

Doing some research, I found replacement tailstock locks on the axminster website, where the screw has a nose on the end which I assume would then slide into that groove. (Link: https://www.axminstertools.com/axminster-tailstock-locking-handle-600419). I'm wondering if my tailstock lock should have such a nose as well...

Would anyone who owns that lathe or has experience with it be able to shed some light on this?

Thank you

 

[Jamesc]

I don't have this lathe, but it is common practice on many lathes for the lock to have a 'Nose' which engages with the slot in the barrel.
Check that the barrel is aligned with the screw and make sure it is not wound out too far. On my lathes a half turn is all that is need to lock/unlock the barrel. If the 'nose' is missing then the replacement part is cheap enough and should solve the problem.

 

[ChaiLatte]

The tailstock lock is simply a screw. So nothing is engaging with this groove.

Where is the lock in relation to the horizontal centreline of the barrel?

If you remove the lock and shine a torch into the hole, do you see the groove in the barrel?

The locking screw would probably require what is called a 'dog point' so it provides rotational alignment when loosened slightly (1/4 turn) but presses sideways against the barrel when tightened.

If you look at the one to which you link, you see the dog point at the end of it.

Remove the screw and the barrel and see if the point on the screw you have fits the groove in the barrel. It may have mushroomed through abuse. That is easilty fixed.

 

[ThornOfCamorr]

Thx for the input!

If you remove the lock and shine a torch into the hole, do you see the groove in the barrel?

Yes, those align.

I'm confident now that the locking screw is missing the 'dog point'. The screw is a M10, 18mm long. Sounds like the Axminster replacement part will fit, so will order that one.

Thank you again

 

[ChaiLatte]

I'm confident now that the locking screw is missing the 'dog point'.

Have a look at the end of the one you have. Does it look as if the dog point may once have been there?

It is possible that it has been sheared off. You could envisage using a large auger or forstner bit in the tailstock and either a tough piece of wood or a snag. That dog point is the only thing resisting the rotational force of the drill bit so could be the weak link.

It could also happen if someone winds in the tailstock too rapidly or enthusiastically. The barrel would bottom out on the screw and then if force (momentum) remains on or from the handwheel, the dog point would feel it and may throw in the towel.

See what conclusion you come to and if it looks at all dodgy, consider supplementary ways to make your tailstock resist torque loads when the operation being performed demands this ability.

 

[ThornOfCamorr]

Have a look at the end of the one you have. Does it look as if the dog point may once have been there?

Hard to tell, honestly - it doesn't look like the surface I'd expect from a new screw, but that can mean many things... could just be worn from requiring to do a job it was not designed for.



Here some more pics from the rest of the tailstock parts:

 

[Amplidyne]

Looks like the keyway has had some hard use, which makes me wonder if the end of the bolt that acts as a key hasn't snapped off as already said.
Is there another threaded hole underneath the tailstock that the key pin is meant to go in?
I'd have sort of expected the lock to be separate.

 

[ThornOfCamorr]

Yeah, I expected the lock to be separate as well. I expected a hole for a grub screw or a pin or something. Only thing I could find underneath the tailstock was a rather stiff spider

I think the hard use on the keyway is due to the broken/wrong lock key pressing against the edge of the keyway.

 

[ChaiLatte]

If you had a metalworking friend, it would be possible to drill and tap the tailstock casting in one or more places at the same level as the locking lever. You could then loctite in a couple of dog point grub screws, to act as the rotation-prevention keys (screw them in snug and then back off 1/3 of a turn before the glue sets).

That would demote the locking lever to a one trick pony - locking.

The wear on the keyway could be explained by someone loosening the locking lever too much, so it is only the dog's nose that is poking into it. That would wallow it out at the outer perimeter as the photo shows.

 

[SVB]

If you had a metalworking friend, it would be possible to drill and tap the tailstock casting in one or more places at the same level as the locking lever. You could then loctite in a couple of dog point grub screws, to act as the rotation-prevention keys (screw them in snug and then back off 1/3 of a turn before the glue sets).

Careful- the dog screw is at the front on purpose else the quill will not advance very far!

 

[Amplidyne]

The tailstock on my metal working lathe (A Chinese one) is like I described. It uses a dog point end grub screw and locknut as a key. It's just about OK after a remade grub screw, and careful and judicious filing. The lock works on the side as I already said. It's removed most of the slop, and given a fairly smooth advance of the quill. Strikes me as well, that as Chailette has suggested, someone who knew what they were doing could drill and tap the tailstock for a separate grubscrew.

 

[Fergie 307]

Poor design really to have the one part perform both functions. But it is what it is. My only observation would be that you might consider making the replacement out of something like brass, so it doesn't eventually damage the slot. You could do this easily enough by drilling the end of your existing one and inserting a suitable diameter brass rod to actually engage with the slot.

 

[ChaiLatte]

Just as a little food for thought, please consider the way tailstock barrel rotation is prevented on a Myford ML7.

https://www.myford.co.uk/product/er23-barrel-key-70-1507/

It does require the keyway to be full length as the key has to be inserted from the inside out. The little nub projecting in the pictures has to be filed off.

 

[ThornOfCamorr]

Well, I guess this is where one finds the differences between a cheap and an expensive lathe....

I've ordered a replacement keylock with dog nose. I'll inspect fit once I got it.

Plenty of good ideas in this thread, thank you so much. Unfortunately I've no metal working friends, but I should manage to drill into the old keylock to insert a brass rod. I'll assess the situation once I've the new keylock and make a more informed decision then. Happy to keep you posted

 

[Amplidyne]

Well, I guess this is where one finds the differences between a cheap and an expensive lathe....

It's the same with the metalwork lathes. They're OK basically for what they are, but the finish and QC is pretty hit or miss, and mostly miss.
I've got a Chinese "8 X 16" which are all pretty well the same whoever puts their badge on them. They OK, but mine is quite heavily modded now, and has pretty well been apart, and reassembled carefully with the mods.
The dog point grub screw was just a plain grub screw, and the threads had been chewed up by the tailstock quill being used. I turned a correct sized end on a decent quality grubscrew, and it took out a large part of the slackness in the job. I've considered making a mod something like the ML7 one mentioned, but it'll have to wait.

I've been making long overdue improvements to my workshop / garage. It's coming on, although at the moment it looks like a lunatic has been piling stuff up in the middle. (I have.) Still that's another story.

 

[Fergie 307]

The Myford style won't work in this case because it has to perform both functions. So to lock the spindle it has to turn to push the end against the bottom of the slot. That precludes you from using a square or oblong key. You could have a free floating key that the screw bears against to lock it, but looking at the casting there isn't enough meat in it to allow for that. I think you are stuck with the existing design.
As Amplidyne says the pin on the end needs to be a nice snug fit in the slot so it doesn't allow the shaft to rock about it's axis, and long enough so that when it is pressed fully into the bottom of the slot the threaded section doesn't protrude into the bore and get damaged itself, or cause damage to the edges of the slot.
On most high quality lathes you have a key like the Myford one to control just rotation, and a separate device to lock. This is often a heavy bar with a half round slot ground in it through which the spindle passes. This is pulled up by a screw to lock the spindle very firmly in place. A much better design, but requires more parts and a more substantial casting to house it, so much more expensive.
What you have is fine for a hobby machine, so long as you treat it with care.

 

[ChaiLatte]

The Myford style won't work in this case...

Add in additon to existing lock, where blue dot is shown. Reduce diameter of existing lock so it cannot touch sides of keyway.