Bridgeport Saddle Stuck

I have a Bridgeport J-Head that has a saddle that is stuck / very difficult to move. When I crank the cross feed towards me, for the first say one or two turns, its moving freely, but you can feel it binding and at the 3rd turn, its very difficult. Move it away from you and it's the same scenario. So I imagine something is binding/gunked up under the dove tails in/around the saddle. Thoughts on procedure to free this up? Remove table and saddle to clean? I'll need some pointers on the removal of the table if that is the case.

Thanks in advance. Any information would be extremely helpful.

Make sure the table lock (left side of saddle) is completely freed up.. What is the age of the machine? It could be gunk as you say, it could be some variety of other issues or more than one issue. Is the "stuck" behavior throughout the entire travel, or can you tell? Removing the gib may give you some additional info. In any case, make sure that you have got some way-lube on the ways and the sliding surfaces aren't dry and just scraping on each other.

specfab said:

Removing the gib may give you some additional info. .

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Best to remove table first, when fully pull saddle.
May as well inspect all the way.
Issue could just as easilly be the cross-feed screw.
Remove the 4 bolts around the Y screw-housing.
This will let you know if the binding is in the saddle or the screw,
by allowing which ever to move now.

If you try the Y-gib pull, ballance the table gravity first!!
If you have the old heavy Feed-box, this won't be the middle.
m1m

All locks are untightened and appear to be free. Ways are good and oiled. It will move freely towards the machine for a turn or two-then begin to bind. Crank cross feed so saddle/table move towards you and it begins to tighten up again. So it will move freely in either dierction, then begin to bind - like it's attempting to try to move over something or something is building up in either direction. I loosened up the y-axis gib some and that seemed to help a bit but again, moving in either direction it starts to do it again. Wondering if something is on the cross feed screw? Will remove 4 bolts to see if the binding is in the saddle or screw. Thanks for the advice thus far-anything you can offer up is wonderful. Thanks again.

Did you just get the BP and notice this problem? Or, have you had it for some time and this problem just started?

I've had it for about 2 years but it's been sitting/stored waiting for use in my shop. I check things now and again - discovered this today.

Removal of the 4 socket head cap screws holding the cross feed bearing bracket in place has revealed that the saddle freely moves towards you. I can push the saddle freely towards the body of the machine pretty easily. So I'm suspecting perhaps something with the cross feed screw? To expose the cross feed screw do I simply pull the saddle towards me to expose? Reason I'm asking is this is the first time I've done anything to the saddle - replaced bearings in heads etc. before but never had to deal with the saddle / table before. Just want to make sure I'm proceeding correctly.

Thanks for all comments-they are greatly appreciated and have helped.

To answer a previous question: serial number is BR-69494. So 1964 if I've done my homework correctly.

The nut is one bronze casting, that does both screws.
Take the 'X' screw out.
take the 'X' (Table) gib out.
Remove the table. !! Not a solo job.
Too easy to loose it even if you are strong enough.
You should be able to fully examine the Y screw and the nut condition.

Disclaimer;
Been over 20 years since I did this.'
Brain-fade has taken a toll.
m1m

Line up the marks on the front of the table, remove the set-screw from the center of the table and shoot some way lube in the hole.

The screws propbably have not been oiled in ages and they are just dry.
JR

Also, pull a zerk out and see if there is grease in it, if there is than that is part of your problem, that machine was meant to have way oil in the zerks, not grease. The old grease will harden and make everything hard to move and wear the bronze nut and lead screws out faster from pulling so hard. You should plan on taking it all down and cleaning it all out if there is grease in it.

Remove the four cap screws the hold the bracket for the Y-Axis.

Pull the Table/Saddle towards the operator side, towards you.

Look for the two fasteners, screws/cap screws on the bracket side facing you.

The small fastener is the keeper, remove it.

The larger fastener is the adjuster that 'compresses' the leadscrew nut, remove it.

Pull on the leadscrew until the nut is removed from the bracket.

Leaving the gib in and using the clamp may help hold the saddle in place.

Clean the parts and see if the nut travels freely across the length of the leadscrew.

This is what I think is going on here.
The Y-axis leadscrew has wear in the center of travel. Not a surprise. But, the leadscrew nut has been 'compressed' to compensate for the slop generated by wear.

What to do: Check the leadscrew for wear using a single thread wire. Do a comparison of the middle and extremes. If wear is excessive, chase the leadscrew threads until the depth is close over the length. Or make a new one. Or purchase a new leadscrew and nut.
The nut might be squashed too much. Put a couple of screwdrivers in the slots and try to spread it apart 'a little' from the center. Check the fit, you like? Reinstall.
I have made Y-axis leadscrew on a 10" atlas using follow rest and steady rest, easy job.

Warning: Overtighten adjuster nut when refitting/installing leadscrew will crack the knuckle casting.

Good Luck,
John

You could also purchase threaded rod. Get precision grade, the other type might be rolled thread.
A six foot length should be enough for two leadscrews. Check for left or right hand thread!