Bridgeport broken T slots

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kansas rust buzzard
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Bridgeport broken T slots

Post by kansas rust buzzard » Wed Nov 01, 2017 9:27 pm

Hi, I just purchased a Bridgeport with a 9x42 table, a J1 model. It has one major problem, someone broke several places in the table, I don't know if they did it with lifting a clamp up or what, but both ends have chunks broke out and one near the middle right. They are old breaks and I don't have the pieces, I am thinking of milling out a step as deep as the top of the T slot and making some step headed bolts to tap into the table and cut off after I secure a chunk of cast iron, then stone smooth? Might be able to make a dove tail and drift in on some of them? I might be able to nickel weld it but I don't want to warp anything, its a nice little mill, it should clean up pretty and although I could work around these flaws its going to bother me. Thanks for any advice.

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SteveM
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Re: Bridgeport broken T slots

Post by SteveM » Wed Nov 01, 2017 10:31 pm

My guess is that you are correct that welding would risk a warp.

The breaks were likely due to clamping things without having the clamps close to the piece being clamped, so that there is nothing above the table to resist the nuts pulling thru.

If you can work around the breaks, that is, clamp stuff to the table using the intact areas, then leaving it alone may be the best option.

Can you post a picture so we can see how bad it is?

Steve

kansas rust buzzard
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Re: Bridgeport broken T slots

Post by kansas rust buzzard » Wed Nov 01, 2017 11:27 pm

I may have to try to post pictures tomorrow night as I am knew here and not figured it out. I try to attach and it shows a green bar loading them and then when its fully loaded something goes wrong. Thank for the reply, I will figure out how to post them somehow.

John Evans
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Re: Bridgeport broken T slots

Post by John Evans » Wed Nov 01, 2017 11:29 pm

Often caused by using T nuts with threads clear through instead of last thread incomplete . Specially when using bolts rather than studs. Best advise be sure the edges around the broken areas are not proud of the table surface and leave it otherwise alone !!! A lot of effort for a cosmetic result.
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SteveM
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Re: Bridgeport broken T slots

Post by SteveM » Thu Nov 02, 2017 7:26 am

kansas rust buzzard wrote:I may have to try to post pictures tomorrow night as I am knew here and not figured it out. I try to attach and it shows a green bar loading them and then when its fully loaded something goes wrong. Thank for the reply, I will figure out how to post them somehow.
Your pictures are too large. Open them up in paint and resize them down maybe 50%. Make copies of them first if you want to keep the originals at full resolution.
John Evans wrote:Often caused by using T nuts with threads clear through instead of last thread incomplete .
Yes. If you can thread the stud or bolt completely thru your t-nuts, put the t-nuts in a bench vise, grab a cold chisel and a hammer and put a ding in the end of the hole that faces down when installed. That will bugger up the threads enough that a bolt/stud will either not go thru, or you will feel enough resistance to know to stop.

Steve

earlgo
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Re: Bridgeport broken T slots

Post by earlgo » Thu Nov 02, 2017 9:54 am

If your breakouts are not too long you could make special long T-nuts that are longer than the breakout. This might get you through a tough setup situation. I've got a breakout on the end of the HMill table and so far it hasn't been an issue.
table breakout.JPG
Table Breakout
One of the shop managers I worked with used his Bridgeport table to straighten a bent lead screw. It gave me the willies to see how much torque was put on the clamp bolts. I was expecting a table failure at any moment, but it all came out all right and the screw was straightened as good as new(almost).
--earlgo
Deja Poo - The feeling you have seen all this crap before.

kansas rust buzzard
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Re: Bridgeport broken T slots

Post by kansas rust buzzard » Thu Nov 02, 2017 9:19 pm

Thanks everyone, here is my new try at posting a photo. This is probably the most troublesome place, its right of center on the near slot, not really where I would want a vice but I might get used to it? I am probably too worried about it but I am kind of OCD about having old tools look nice. The mill had not been used in decades and is dirty and some surface rust but appears tight from what I can tell. I have had other mills but never a Bridgeport so I guess for the first one I should just be happy? Thanks again.
Attachments
Table half size.jpg

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neanderman
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Re: Bridgeport broken T slots

Post by neanderman » Thu Nov 02, 2017 11:27 pm

Just a thought, but could you fill them with something like epoxy? You wouldn't want to clamp there, but it could give you a flat suface.
Ed

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SteveHGraham
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Re: Bridgeport broken T slots

Post by SteveHGraham » Fri Nov 03, 2017 11:22 am

John Evans wrote:Often caused by using T nuts with threads clear through instead of last thread incomplete . Specially when using bolts rather than studs.
Now there is a hazard I didn't know about.
Every hard-fried egg began life sunny-side up.

tornitore45
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Re: Bridgeport broken T slots

Post by tornitore45 » Sat Nov 04, 2017 8:28 am

If you have any T nuts with a complete thread make sure to buggar the end so the the stud will not go through. I have done it with a square chisel or it can be done with drift by crushing the last thread.
Mauro Gaetano
in Austin TX

Ironman1
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Re: Bridgeport broken T slots

Post by Ironman1 » Sat Nov 04, 2017 10:46 am

If it was mine, I would use NiRod and build it up with nickel. Or use NiRod to weld in a chunk of steel. I do a fair amount of cast welding and sometimes on transmission mount pads for tractor fork FEL frames the missing chunk is so big I replace it with steel. When doing frozen engines, and the area is big, I zipcut out a piece of cast from another engine block. Because of the engine heat I want to stay with the same metal.

In your case, I would warm the table with a flame or electric heater, and use the cold stitch method, in which you stop and peen the weld every inch or so, and never get it too hot to hold your hand on it.
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Richard_W
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Re: Bridgeport broken T slots

Post by Richard_W » Tue Nov 07, 2017 10:00 pm

SteveHGraham wrote:
John Evans wrote:Often caused by using T nuts with threads clear through instead of last thread incomplete . Specially when using bolts rather than studs.
Now there is a hazard I didn't know about.
We talked about this some years ago. I have seen big machines with 7/8" studs have the tables broke in several places because of the stud going all the way through the T nut. That is why the stud sets are not tapped through on the T nuts. To avoid this problem. Only thing is a lot of people insist running a tap through all the T nuts so the studs go through.

Richard W

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