# Bridgeport Leadscrew Problem....?



## EmilioG (Jan 20, 2016)

Hi,

I would like to repair the BP 2j Variable speed mill where the leadscrew is very tight and hard to turn when it gets further away from the table towards myself.  The handle gets very difficult to turn.  It goes in toward the rear and gets easier to turn.

Can anyone with BP rebuild or repair experience diagnose this problem for me?
I know I will have to take it apart. What will this entail and what tools and parts will I probably need to buy?  Thanks


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## timvercoe (Jan 20, 2016)

Don't know about tools and parts.  Maybe some one can help me here......I know the X axis had a split in the nut and a pinch bolt to adjust out the backlash.  I don't recall if the Y axis does or not.  If it does and some one has adjusted it to tighten up the back lash, the lead screw could be worn in the middle such that the screw works easy in the middle but binds in the nut on the ends.  Another possibility is wear in the V ways for the saddle are loose in the middle and tight on the ends.  The correction for this would be scraping away material to flatten 'and true the V ways.  You might try to adjust the gib and see how it effects the motion.  This could give you an indication of what to look for.    I worked on a Gorton mill a few months ago that some one had added brass shims to the V ways to tighten up the play.  It too would work fine in the middle motion and almost become impossible to move at the extremes of travel.  I took out the brass shim stock and adjusted the Gib, it seemed better.  I didn't cut any thing with it after that so don't know about the "proof in the pudding" so to speak.  If the screw is loose, worn in the middle, I just happen to have one that I ran across today.  It's a new screw from an acura turn that had been replaced by a ball screw for a CNC conversion.  The acura turn is a BP copy,  the screw might be the same.     

Tim


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## Ed ke6bnl (Jan 20, 2016)

I have a lot of free play in my x axis how do you go about tightening the split nut?


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## timvercoe (Jan 20, 2016)

It's been a long time since I was in my machine  under the table,  It seems to me that you can run the table all the way one way and then tighten the screw with a long blade screw driver.  I can look at my machine tomorrow when I get to the shop and see if it will jog my memory........ You might want to PM me to remind me to do it. 

Tim


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## timvercoe (Jan 20, 2016)

Another thought, if you have to take the table off the machine, it is heavy and remember it is a precision instrument, you don't want to drop it.  Be prepared, engine hoist, crane etc.  

Tim


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## Ed ke6bnl (Jan 20, 2016)

thanks, would be nice to get some of the play out of the screw, but things are sure nice with the added DRO even with the play. on this old 1955 Bridgeport.


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## ARKnack (Jan 20, 2016)

Ed ke6bnl said:


> I have a lot of free play in my x axis how do you go about tightening the split nut?



It depends on the nut you have. I have a Comet mill which is a BP clone. It had a locking screw I had to loosen, then I could led tighten the split nut.  Othe instruction I seen was you had to remove the nut and finish a saw cut that sliced the nut in half. Then there was an adjustment screw to tighten it. I am sure there are some YouTube videos showing how to do that.

If your mill is old, I would suggest you remove the table and clean/inspect it. On mine I found plugged oil ports and lines, so only prat of the ways were getting oil. It isn't really that hard to remove the table


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## EmilioG (Jan 20, 2016)

Yes. An overhaul is in order.
The bijur one shot is stuck as well.
Might be all plugged up.
Engine hoist?

Thanks to all.


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## EmilioG (Jan 21, 2016)

Where is the best place for BP parts? H&W Machinery? or here>>
http://www.icai-online.com/leadscrew-assembly/


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## Snell Metalfab - Joe (Jan 21, 2016)

I've been working on my newly acquired 1971 Bridgeport Variable Speed head and have found H & W Machinery to be most helpful.  They have nearly everything (they have had everything I needed, but that's been limited) right in stock and their prices seem fair enough.


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## Kernbigo (Jan 21, 2016)

i just fixed a bijur pump by draining it and dumping kroil's in it, took a couple hours but it worked through ,you can by it direct from the co.


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## ARKnack (Jan 21, 2016)

The easy way I found to remove the table was to use a heavy work bench. My mill table is a 10x50 and I was able to remove it by myself.
What I did was cranked the table all the way to the right. Removed the cranks & lead screw. Place the bench (steel top works great) next to the mill underneath the mill table. Lower the Z axis until the table was just touching or about to touch the bench top. Finish pulling the table onto the bench. The bench I used had casters on it so that made it super easy.
Putting the table back on was just the opposite. I did need help aligning the table and pushing it on at the same time. What is nice is the table is already on the bench so you can flip it over to work on. I did not remove the knee.
I had to replace a couple oil feed line and unplug several port.


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## dlane (Jan 21, 2016)

OP, you may want remove the Y Front chip cover and look in there, could be a bunch of junk making Y movement difficult. 
Just a thought


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## AlxJ64 (Jan 21, 2016)

I just replaced the lead screw nut in my '43 M head Bridgeport. Its not at all difficult. You actually don't need to full remove the table. Atleast I didn't have to but I did for the sake of cleaning it all. You can remove the right side of the x axis handles, and you may need a puller, to pull the handles. Then do the same for the left side and then thread the leadscrew out, and then carefully slide the table back to the right and that should give you reach to the cross slide area of the leadscrew... Photos...




Ad for the adjustment of the split nut. There should be that screw there... If the nut is split, and you have a gap cut as well, as you tighten the screw in the side of the nut retainer it will apply pressure on the threads between the two nuts and this closes your BL. Its really simple and works. The new nuts from H&W are split already, at least mine were.

You can also remove the bolts in the front of the Y axis and thread it out and then remove the entire cross feed nut assembly and replace both while you are in there.


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## dlane (Jan 28, 2016)

Seems you have grease zerts on the table , my machine has some also, I can't find an oil can that has zert fitting on them.


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## ARKnack (Jan 28, 2016)

There are oil guns out there but are pricey. Common practice is to convert a grease gun to an oil gun. Google it. Only problem is you have to hold the gun upside-down  for it to work. There was a magazine article (HSM??) the show a foot pump version . Looked cool.


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## RandyM (Jan 28, 2016)

Here is what I bought. Lube Pump It is perfect for the hobbyist.


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