Bent Quill Bolt on a 3520?

[Rusty Fleeman]

When I run out the quill on my Powermatic lathe, it is as smooth as the day I bought it from about the 3" mark until it unthreads. From 3" down to 0, it gets gradually stiffer to the point it almost takes two hands to turn. I pulled it all apart today, checked for damaged threads, debris, & lubricted the assembly. Out of the tailstock, the two pieces thread fully with ease. When reassembled, It's not as stiff, but still a far cry from what it should be. Any chance I have bent the quill from drilling to large of a hole and too far extended? Any help or thoughts are appreciated in advance!

 

[Bill Boehme]

There are one or two screws on the back side of the tailstock that ride in the keyway on the quill. Sometimes the end of the screw presses directly against the keyway slot of the quill and other times there is a key between the screw and the keyway.. It might be that this is adjusted too tightly. While you have the quill out, you may as well look for burs or rough spots in the keyway. It's not very likely that the quill is bent. I would think that it has something to do with a bur or bad machining somewhere. Also look in the tailstock bore for a suspect. If you have a good steel straightedge you could check for a possible bend. If you have a slab of granite from a granite counter top that makes an excellent granite surface plate for a lot less than buying one from L.S.Starrett.

 

[john lucas]

Bill is dead on. It would be really simply to check for bent quill. Just use a good straight edge and check it on at least 4 sides. That should eliminate that pretty quickly and like Bill said it would take a lot of force to bend it. Check the pins or screws (depending on whether you have a 3520 A or B) to make sure they aren't too tight or could be possibly too loose and the screws could be trying to come out of the slot. You could also remove the handwheel and screw and put the quill in backwards to see if binds.

 

[hockenbery]

Drilling does damage the keyslot on some lathes. If it threads easily out of the lathe the problem is most likely the the ram or some part of its channel binding

I bought a second hand General that was binding when the ram was brought in all the way.
I ended up grinding a little bit of the casting away and now it runs smoothly. Used a dremel with a cut off wheel.

 

[Clifton C]

Since it threads outside the tailstock, I would suspect the quill. If you don't have any prussian blue (permatex is one) Sharpies or dry erase markers can be used instead. Clean off all lubricant and "paint" the quill with a sharpie, either the whole thing, or just suspect areas. Reassemble, run the quill in, then out and look for rubbed off ink. Obviously some ink just rubs off, but shiny bumps are more prominent and may be the culprit. I do maintenance on some school lathes and it's usually the edges of the keyway that gets munged up, a few judicious passes with a fine file usually returned things to order.

 

[Mike Johnson]

If you are unable to determine the root cause, a bigger hammer is usually the solution.
A good cleaning of the components and close examination should located the root cause.

 

[Steve Worcester]

Put a metal rule against the outside length of it and check that it is still straight.

 

[Mike Peace]

Since it threads outside the tailstock, I would suspect the quill. If you don't have any prussian blue (permatex is one) Sharpies or dry erase markers can be used instead. Clean off all lubricant and "paint" the quill with a sharpie, either the whole thing, or just suspect areas. Reassemble, run the quill in, then out and look for rubbed off ink. Obviously some ink just rubs off, but shiny bumps are more prominent and may be the culprit. I do maintenance on some school lathes and it's usually the edges of the keyway that gets munged up, a few judicious passes with a fine file usually returned things to order.

Right on. This is exactly what I found on helping a friend with his 3520b. The machining of the quill in the Tailstock is very close. If the quill locking screw gets loose and rubs on the edges of the slot, it can raise an edge. The damage is not always visible to a casual look.

 

[Rusty Fleeman]

Bill is dead on. It would be really simply to check for bent quill. Just use a good straight edge and check it on at least 4 sides. That should eliminate that pretty quickly and like Bill said it would take a lot of force to bend it. Check the pins or screws (depending on whether you have a 3520 A or B) to make sure they aren't too tight or could be possibly too loose and the screws could be trying to come out of the slot. You could also remove the handwheel and screw and put the quill in backwards to see if binds.

It's a 3520b.

 

[Raul McCai]

Any chance I have bent the quill from drilling to large of a hole and too far extended

Oh gosh I have a 3250b and I can't imagine the kind of shock it'd take to bend that quill. I should think you'd know it if you incurred such a moment.. Use a straightedge and a light. I bet it's not bent.

 

[Bill Boehme]

Have you identified the cause of the problem yet? I looked at the online manual and saw the there is a setscrew and jam nut on the backside of the tailstock and the locking screw is on the top of the tailstock. It's not at all uncommon to find a bur on the edges of the key slot. I've had to file a bur off the quills in my lathes several times

 

[Rusty Fleeman]

Have you identified the cause of the problem yet? I looked at the online manual and saw the there is a setscrew and jam nut on the backside of the tailstock and the locking screw is on the top of the tailstock. It's not at all uncommon to find a bur on the edges of the key slot. I've had to file a bur off the quills in my lathes several times

I have not had the opportunity to disassemble the tailstock again today. Hopefully after Christmas I can get back into it. I appreciate everyone's input and will report back with what I find.

 

[john lucas]

I've repaired a few lathes for people over the years and almost always it's either damage done to the slot in the quill or the screw has been misadjusted and rubs the slot.

 

[Rusty Fleeman]

OK, I got back in to the tailstock today. I removed the set screw from the backside and the brass lock from above. I filed a burr from the groove in the quill and I gave the whole quill a light sanding with 800 grit to rule out any CA, or other undetected gunk on the quill. It now travels easily from the 2" mark to fully extended. From 2" in to auto eject is much easier but still not as smooth. Pulling the bolt again and taking a light to the inside of the tailstock to hunt for burrs next.

 

[Bill Boehme]

Also look for rust. The bottom of the keyway may be rough from years of use and a light filing to clean it up using the side of a file might help.

 

[Rusty Fleeman]

After closet examination, I found w subtle "bulge" above the keyway around the 2 3/4" mark rather than a burr sticking. Filed it down, lubricated everything and reassembled. Runs the full length more smoothly than the day I bought it! Thank you all for your advice and guidance. I'm an amateur woodworker and now a shade tree machinist! Back to making good wood shavings!!