Possibly a very silly question

[cooper1203]

Hi all, Maybe this is a silly question but im not 100% sure of the answer as i am new to all this.

Yesterday i got to the point of tackling the headstock of my atlas 10f lathe. There is a collar that holds in the spindle and preloads the bearings. There is supposed to be a set screw with a little bit of brass underneath to protect the threads. Both the set screw and brass were missing and mr bodge and bugger it used the hole to knock the collar loose with a drift and elongated it to the point that i had to do the same to get it off.

Question is can i drill and tap another hole in the collar or does a set screw hole have to be in a certain place to work. (i did warn you all it was possibly a silly question) or have i got to try and source a new collar?

second question is what size do i need or again does it not matter with in reason?

Many thanks

 

[extropic]

Yes, you can relocate the set screw.
Size? Are you saying that the original hole is so buggered that you can't guess what size the thread was?
Guess what size it was. I would choose a fine thread over course.
Actually, I like using a nylon sphere (or slug) instead of a brass tip. The nylon will distort and conform to the spindle thread as well as the tapped hole thread (so it's not likely to fall out accidently even if the set screw is removed). Put a nice smooth tip on the set screw so it doesn't tear up the nylon.

 

[markba633csi]

I think the original setscrew was 10-32

 

[cooper1203]

thanks for the responses

@ extropic the hole is very badly elongated. I will see if i can find the nylon inserts that you described as i would have to buy the brass anyway and your suggestion sounds like a better bet.

@ markba633csi Thanks ill go for one of them then

 

[GeneT45]

Another soft tip is a piece of lead shot / lead wire. Also conforms to the threads and I think gives a more secure grip.

GsT

 

[RJSakowski]

I second the lead. Another good choice would be solder. Almost a dead cert that you have some and you can easily melt and shape a small amount to make a slug to fit your newly tapped hole.

 

[ChazzC]

You can also buy set screws with soft tips (brass or nylon); the advantage of these over the cheaper alternative of using a separate piece is that the soft tip backs out with the set screw and won’t potentially jam between the collar & spindle.

 

[ptross]

a soft tip would be great on a smooth shaft, but would get chewed spinning on threads.

 

[ChazzC]

a soft tip would be great on a smooth shaft, but would get chewed spinning on threads.

OT-ish:

Not super helpful in this case, but in fixing/modifying other tools I have added a groove in a threaded shaft for a set screw to land to prevent this issue.

Back on point, yes, the soft tip will get chewed up on the threaded spindle, but it’s sacrificial and is a low cost (even at $5 a pop) alternative.

 

[cooper1203]

maybe im being thick here and certainly not trying to teach anyone with far more experience than i have to suck eggs but if i backed the set screw out or even removed it and then tightened the collar to set the preload then put setscrew back in will it still get chewed by the threads?