Worn Tailstock - How to Fix?

[Phil3]

How worn can be a tailstock be before problems begin to arise, such as a drill wandering off center (despite a center drill hole)? My 1946 vintage Southbend 9A tailstock shows some slop. Enough to cause some problems I think. With the spindle extended enough for me to measure lateral spindle movement at a point that is 1.5" out from the tailstock casting, I get the following.

Horizontal movement: .003"
Verical movement: .004"

Add an arbor to the tailstock spindle, plus a keyless chuck, and a drill bit, that long assembly multiplies the few thousandths substantially.

Near the drill chuck face, the vertical movement is .010", with only modest pressure on the chuck. You can see oil being squeezed out between the tailstock spindle and casting. The same thing happens when drilling starts. Despite a pilot hole, the drill bit tries to walk around and the tailstock spindle moves a bit under this force.

I have tried to make sure the drill trying to run around with the spinning stock is not due to tailstock misalignment, but maybe it is still off.

If the tailstock is worn, I may be in a bad spot, as I see no good way to fix this, and any replacement tail stock may be as worn as this one.

- Phil

 

[Tony Wells]

That's not an abnormal amount of movement for an unlocked tailstock. Your drill wandering probably is due to other causes. Main thing I would be concerned about is movement while it is locked, as in while holding a live center during a turning operation.

You're probably right. Another tailstock would not be guaranteed to be any better, and could present other alignment problems in the vertical plane that would be harder to fix.

If you really wanted a precision tailstock, you would have to hone or grind the ID and build up or make another spindle to fit it. And you do need some clearance after all. I believe you would see only minimal gains, overall, after considerable expense and time.

 

[Davo J]

There was a guy on the PM forum who you could send you tailstock to and he would bore it out and make a new quill for it. From memory it wasn't very expensive but am not sure where the thread is, you would have to search it. He only did is for pocket money and it wasn't a business.

Dave

 

[brucer]

How worn can be a tailstock be before problems begin to arise, such as a drill wandering off center (despite a center drill hole)? My 1946 vintage Southbend 9A tailstock shows some slop. Enough to cause some problems I think. With the spindle extended enough for me to measure lateral spindle movement at a point that is 1.5" out from the tailstock casting, I get the following.

Horizontal movement: .003"
Verical movement: .004"

Add an arbor to the tailstock spindle, plus a keyless chuck, and a drill bit, that long assembly multiplies the few thousandths substantially.

Near the drill chuck face, the vertical movement is .010", with only modest pressure on the chuck. You can see oil being squeezed out between the tailstock spindle and casting. The same thing happens when drilling starts. Despite a pilot hole, the drill bit tries to walk around and the tailstock spindle moves a bit under this force.

I have tried to make sure the drill trying to run around with the spinning stock is not due to tailstock misalignment, but maybe it is still off.

If the tailstock is worn, I may be in a bad spot, as I see no good way to fix this, and any replacement tail stock may be as worn as this one.

- Phil

have you checked to see if the tail stock is centered with the lathe chuck with the tail stock is clamped? use a mag base and indicator and clamp on a straight reamer or dowel pin and swing the indicator around the reamer or dowel pin near the tip of the drill chuck.. you can also move the tail stock forward and back to check it at different location on the ways.. check it with the tail stock in the housing and also extended out of the housing...

also check the center line of the bore of your tail stock.. remove the drill chuck and swing the inside of the taper. you might have a flaky taper either on the drill chuck or the tail stock, a worn taper could also give you fits..