Tail Stock lock

[Susquatch]

Castellated nut with a cotter pin would solve the problem nicely as well.

Yes, for me that's probably a better solution. No idea why I never dealt with this earlier. I guess it was just easy to live with it.

 

[YYCHM]

I have this problem on my tailstock too. The nut slowly backs off with use and sooner or later the lock handle won't lock anymore. Sometimes I don't notice it until the tailstock starts moving backward on me. It's never bothered me enough to fix it permanently. I just pull the tailstock off and give the nut a turn or two. It would be nice to be done with that forever with a mod like this.

Thank you!

Thread locker

 

[Susquatch]

Thread locker

Ya, prolly would work too. Sometimes simple is best.

But I love the castle nut idea because it's guaranteed to be impervious to the locking cycles that nut sees. I should have used locktite back the first time it happened. Then again, I prolly never would have made a castle nut for it if I had done that.

 

[Dabbler]

thanks for the spring idea, @whydontu !!

My 12X37 lathe solved the nut backing off problem permanently and simply. it has slot milled into the bottom retaining plate the hex bolt sits in, so the reataining plate and nut always turn in sync. If I need another 1/6 turn, I just losen the cam, lift the plate and make a 1/6 turn.

 

[Susquatch]

So, I felt so much better today that I had the guts to go out to the shop. It turns out that the castleated nut idea won't work. I don't even have a nut. I have a bolt head....... Crap.

I may look at some kind of socket block with the same indexing principle as a castle nut - same as or similar to what @Dabbler describes above.

But right now it looks like @YYCHM 's blue loctite is the hands-down leading alternative!

 

[PeterT]

Turns out my stud is M12x1.75. I want to replace or maybe modify the crazy cast T plate. Sorry should have grabbed a picture while it was removed. The stud just dangles through a clearance slot. Hopefully you can see how the notches do not match the bed ways width wise. I might have enough meat in the plate to mill some material & attach better fitting guides. If not, I'll have to hunt down some steel plate & make a better one.

 

[RobinHood]

M12x1.75. Have lots of nylocs or all metal lock nuts. Your choice. Let me know if you want them and how I can get them to you.

 

[Susquatch]

Hopefully you can see how the notches do not match the bed ways width wise. I might have enough meat in the plate to mill some material & attach better fitting guides. If not, I'll have to hunt down some steel plate & make a better one.

I'd be leery of cutting the plate down for a better fit. But one could make and install some alignment bars along the inside of both sides of the plate to center the plate under the ways. It isn't a critical thing. You could even glue the rails on with RTV if you want. They wouldn't take any load. You just want the plate centered so the force is evenly distributed.

Of course, if you make a replacement plate you can do whatever you want. The sky is the limit!

 

[PeterT]

Kind of hard to show with the parallax perspective but I was thinking something like this. Seems to me I already dismissed the idea which is why it looks the same today LOL. For the same or lower effort I could mill something much better from new stock if I had an appropriate chunk of plate. I'm really not sure how they came up with this design. When the handle is loose & TS slides, the plate can rotate to extent the corners catch.

 

[Susquatch]

Kind of hard to show with the parallax perspective but I was thinking something like this. Seems to me I already dismissed the idea which is why it looks the same today LOL. For the same or lower effort I could mill something much better from new stock if I had an appropriate chunk of plate. I'm really not sure how they came up with this design. When the handle is loose & TS slides, the plate can rotate to extent the corners catch.

I was thinking more like this.

Think of the green sort of like Gibb slides or plates - one on each side. The primary advantage is that you wouldn't have to remove any of the original plate. I suppose you could screw them on, but I think RTV would work great and requires no drilling or tapping.

 

[Susquatch]

Btw, my block looks almost identical except the fit is pretty good and the attachment is a bolt sticking up into a threaded hole in the tailstock. In my case nylock nuts and castle nuts won't work. But locktite would.

 

[PeterT]

I guess I have 2 issues with the existing plate
- insufficient contact area with the way undersides. Mine is about like orange line, I could increase to red). If I do heavy drilling, the TS can actually slide backwards which isn't a good thing. I could also make the plate at least 2x longer in the bed axis direction which would provide proportionately more contact area & stability.
- excessive slop in the rotation direction due to the T plate notches being too narrow relative to the bed way width. This would be fixed with the right dimensions.

I just need to drop by Tom Kitta's metal supermarket one day LOL

 

[Susquatch]

I assumed as much already. But I also assumed that it would be enough if you could get it even on both sides. Given your markup photo, maybe that's too optimistic. But you are right, if you can get a big enough plate and can make a new one, then why not? I'd also look at a castellated nut while I was at it, or maybe some other kind of captured nut arrangement.

 

[Tom O]

Could you bevel the lead and trailing edge that should stop it from grabbing.

 

[PeterT]

It might help as you say. But a new, corrected one would ideally solve all the issues simultaneously. Something like this.

 

[YYCHM]

It might help as you say. But a new, corrected one would ideally solve all the issues simultaneously. Something like this.

What size stock would you need to make a new locking block? I might have something that would work for you.

 

[PeterT]

Thanks Craig. Eyeballing 4" x 6" x maybe 1/2 or 5/8 thick? I'll disassemble off the lathe again & draw it up to make sure.
I was sure I had a piece laying around specifically earmarked for this, but it must be hiding.

 

[Susquatch]

I was sure I had a piece laying around specifically earmarked for this, but it must be hiding.

That's what everything you put away for a specific job does.

But don't worry. It will come out of hiding a short while after you buy something else......

 

[Susquatch]

It might help as you say. But a new, corrected one would ideally solve all the issues simultaneously. Something like this.

After I saw how little your current block grabs the bottom of the ways, I concluded that you needed a new block too.

I do wonder why the original is so thick though. Yours looks to be over an inch thick. Mine is around 2 inches. I would have thought that 1/2" steel plate would be plenty. BUT, given the size of the tailstock itself, maybe it needs to be over an inch to achieve the rigidity and reaction strength it needs to have? Or maybe it's just to stop the original cast iron block from shearing at the right angle in the corner of the slides. Or maybe it's that big to force all the stress to be taken up in the bolt shaft that clamps the two parts to the ways?

Those are just guesses. I really don't know why. But I do know that everything bends under load. It isnt whether or not it bends, it is just how much.

If you make the replacement out of 1/2" or 5/8" plate, I'd consider providing for the future ability to add some gussets to increase the cross-section if need be. Or just add them right away - it can't hurt.

 

[PeterT]

I'll take a better picture when the tee block is out. It's a cast iron part & has kind of a relief profile molded in the lower surface for the nut to hide up into. So the net thickness is probably 1/2". Its goofy, almost like it was intended for a smaller lathe.

Providing more clamping area between the tee plate to the way undersides would increase friction holding force for the same lever cam force, which I think is fine. Just spit balling numbers, the current contact area is maybe 3" x 0.25" x 2 = 1.5 in2 vs a larger plate say 6" x 0.75 x 2 = 9 in2 (6x more area). I seem to recall the underside bed rail surfaces may not be ground & the existing plate is rough milled, so also contributes to reduced friction. Its only under heavy drilling that the TS wants to slide backwards. I guess if I was ambitious I could find something like brake liner material in strip form & bond it to the T-plate groove, but it's probably overkill.