mill table trouble

I have an early '60s Bridgeport mill that was rebuilt by a Bridgeport service center in the late '90s. As part of that rebuild it received new X and Y nuts. I have a Servo 150 powerfeed at the R end of the table.

I've been doing a lot of drilling tube for stainless cable railing balisters, which involves moving the mill table coast to coast in the X axis a lot. This morning, with 16 holes to drill in each of 20 parts, the table bound up on me. I removed the table's X feed screw and cleaned it with a brush and solvent and blew it out, and used an ID tube brush and solvent to scrub the X nut ID. While I had the screw out I moved the table by hand, it moves smooth as silk. I blew off the screw with compressed air, and blew out the X nut. Then I oiled the screw with way oil and put all back together. Now it behaves slightly differently - cranking the table to the right is very smooth and easy like it used to be, but going to the left is smooth and hard, meaning difficult. I don't feel any grinding in my hands when I move the table to the left, it's just difficult to turn the handle.

I did lubricate the nuts using the way oil gun. Twice. I tried just using it for awhile to see if it was something that would work itself out, but it doesn't seem to be.

Wondering if somehow my Servo powerfeed is screwed up, I removed the gear that links the powerfeed motor to the table mechanically. Made no difference.

This is a serious problem for me. I need to figure out what's wrong and how to fix it.

Thanks!

Grant Erwin Kirkland, Washington

Reply to
Grant Erwin
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Would this machine have an adjustable gib which might have gotten loose somehow?

dennis in nca

Reply to
rigger

Failed bearing perhaps? The loading is of course different in each direction and the bearing might bind under load and be smooth when not under load. It could also be allowing enough axial play that one of the dials is rubbing when moving the table left. I'd expect the bearing pair on the left end to be the suspect. Looking at the print in the Bridgeport manual there ain't much else there.

Pete C.

Reply to
Pete C.

Not if it's "smooth as silk" moving it by hand with the leadscrew disconnected.

Pete C.

Reply to
Pete C.

I'm interested in the responses to this. I've experienced the same thing intermittently on my Servo 150 equipped mill, but the left-right difference is much less pronounced. On mine, the additional drag is small enough that you probably wouldn't notice if it were the same in both directions.

Ned Simmons

Reply to
Ned Simmons

Proper dial to end casting clearance is listed as .005" - .010" and should presumably not change with direction if the bearings are properly preloaded.

Pete C.

Reply to
Pete C.

in both cases the gib lock is probably not tight as it should be and in moving the one direction, usually the table moving to the left, it will tend to wedge in a little tighter and cause the table to drag a little.

John

Reply to
John

Well, my table gib *was* a little loose. I snugged it up a little, and took the left dial off and carefully put it back on, and now it seems to move a lot easier. Anyway, I'm back in business, so thanks, John!

GWE

Reply to
Grant Erwin

Your gib has to be moving, just a bit.

Reply to
Tom Gardner

This doesn't seem to be the cause in my case. Backing off the gib and resecuring it doesn't help. I think the next step is to try with the power feed removed.

Ned Simmons

Reply to
Ned Simmons

Your gib is either loose or broken. Pull it out and check it.

Gunner

"Aren't cats Libertarian? They just want to be left alone. I think our dog is a Democrat, as he is always looking for a handout" Unknown Usnet Poster

Heh, heh, I'm pretty sure my dog is a liberal - he has no balls. Keyton

Reply to
Gunner

If the gib is loose or broken...they WILL wedge in one direction. On any machine that uses a tapered gib.

Gunner

"Aren't cats Libertarian? They just want to be left alone. I think our dog is a Democrat, as he is always looking for a handout" Unknown Usnet Poster

Heh, heh, I'm pretty sure my dog is a liberal - he has no balls. Keyton

Reply to
Gunner

The problem turned out to be a result of the way the Servo feed is adapted to my mill, a 9x49 Supermax. There's no shoulder on the lead screw extension that Servo supplies, so when the retaining nut for the right handwheel is tightened the whole leadscrew is tensioned, rather than floating on the right end like it's supposed to. I think the best solution is to replace the nut with a threaded clamp collar screwed to the hub of the handwheel, so the collar can be tightened on the thread without tensioning the lead screw.

The adapter for Bridgeport machines does not appear to have this problem.

Ned Simmons

Reply to
Ned Simmons

I am posting this just "for the record". My X axis lead screw was reversed end for end! When I put it back, everything went back together correctly and now all is good.

The moral of the story is: when you remove a Bridgeport table, pay strict attention to which way the lead screw goes in. One table end piece has two bearings; the other has one. The one with two bearings goes on the LEFT END. The screw has a long journal and a short one - obviously, the end with the long journal goes on the left where the two bearings are.

Grant Erwin

Reply to
Grant Erwin

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