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Bridgeport X axis seizing

djb

Swarf
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Mar 3, 2016
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#1
Hi

I have a 1991 Bridgeport with a 48" table and a Bridgeport power feed. I was recently milling down a large aluminum plate which required moving the table in X very close to the stops. Now the table has become extremely stiff and I can barely move it in X, even near the centre of the table where it always moved easily. I have to use two hands to turn the crank and power feed really struggles to move the table. I have checked the bearings by the handles at each end and they are good. I loosened the gib screw two turns and tapped on other end and the gib moved so it is not seized. The table did not get easier to move when the gib was loose. Is it possible for something in the Bridgeport power feed to be binding, even when it is not engaged? Or has anyone ever heard of the brass feed screw nut becoming seized? Usually they wear and become sloppy rather than stiff. Before this happened, there was quite a lot of backlash in the screw (over .100). Wondering if anyone has ever seen this before or might have some ideas where to start? I don't really want to pull the table off if that is not the problem.

Dave
 

tertiaryjim

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#2
Don't force it!
Try pulling the screw out. Take it apart. You might have to loosen the brass nut. If there is a problem with the screw and nut you will find out.
If air has been to blow chips off, then the whole table should be pulled apart and cleaned.
Does the oil which escapes from the dovetails look dark? That's telling you to take it all down and clean.

I remember an old abused machine of which I tightened the brass nut on the X feed as it had something like 0.200" slop.
Couldn't get it all out so ordered a new nut but after sitting a few days it became tight.
When it was changed out the nut was badly worn and was tight in the fit due to chips n dirt.
 

djb

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#3
Thanks tertiaryjim. The oil doesn't look too bad but definitely not clean. It has a one-shot lube and it seems to work well. The machine was partially refurbished before I bought it two years ago but I'm not sure how much disassembly and cleaning was done on the table itself. I will pull the power feed off and see if the screw turns freely. If not, then there lies the problem and I will have to pull the table off. Might be a good idea to clean the ways in any case.
 

JimDawson

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#4
Sounds like there may have been some crud in the lead screw and it got stuck in the nut when you moved the table near the end of travel. Cleaning everything up will probably fix it.
 

chips&more

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Mar 19, 2014
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#5
If you have an OEM power feed (6f of 8F) it will not clear when table gets to that power feed end. The power feed will instead crash into the knee. If this happens the feed screw will probably get bent at that bearing mount or something in that area will be bent or broken. I don’t know about the older OEM gear box feed…Dave
 

djb

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#6
And the prize goes to the two Jim's ... well, there is no actual prize, just this thank you post :D. I wrestled the feed screw out and crud in the brass nuts was indeed the problem. I decided to replace the brass nuts while I had everything apart so I ordered a set from ICAI. For some reason the adjusting screw for the nuts was bent and couldn't be turned so I will replace that as well. Probably explains why there was so much backlash in the screw. There was at least 3/16 inch movement between the two halves of the nut. I always get great advice on this site.

Dave
 
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