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Help! Gib replacement

Rickybob

New member
To make a long story short. I inherited a very nice Bridgeport mill. It’s been in storage 20 years. Purchased new in 1980. Very very good condition.
Problem is the the bed was removed and the gib is missing from the table. Where should I start?
 

n2zon

New member
To make a long story short. I inherited a very nice Bridgeport mill. It’s been in storage 20 years. Purchased new in 1980. Very very good condition.
Problem is the the bed was removed and the gib is missing from the table. Where should I start?

Maybe here?

Homepage - H & W Machine Repair

When I thought I wanted a new gib, they advised me that they must be scraped in. (Then, they told me I should shim behind it instead of replacing it, which saved me some money and a bunch of time.)
 

crickets

Member
H&W sells oversized gibs intended for worn machines, they do require fitting (machining and/or scraping). If the machine has virtually no wear, then perhaps a gib that's made to original spec would work - I don't know the history of how Bridgeport was making/fitting the gibs, it's possible that they were hand fitted to each individual machine, then it basically has to be replicated in your case. Now you could also find a used (somewhat worn) gib and shim it to get the machine in service, but it may cause precision problems and uneven wear, so definitely not a long-term solution.

Bottom line the only way to do it right is to get the saddle and the table to a rebuilder.
 
I haven't taken the gibs out of a ton of machines, but I've never found one that wasn't individually fit by scraping to that specific machine. Even Asian knock off of a Colchester lathe where the compound lock bears directly into the way side of the gib (yes, really, damages it too) has gibs scraped to that specific machine from the factory. I would not expect a new gib to function well in even an unused new machine without at least some scraping/fitting.

It's a skill that can be learned easily enough for this application, but if you don't want to take up scraping as an addiction I'd simply find out what the local machine repair guy would charge to fit a new gib.

For worn gibs shimming behind is an option, as is cutting just a bit off the small end so it can engage deeper. I wouldn't do the latter to an extreme though as you're losing bearing area from the screw end every time you do. In both of those cases though, the worn gib is already an imperfect but close enough match to the specific machine (at least in the center of travel), it just needs to be thicker. This is different from a gib not yet matched to the machine where the surfaces won't quite be at the right angle.
 

crickets

Member
I haven't taken the gibs out of a ton of machines, but I've never found one that wasn't individually fit by scraping to that specific machine. Even Asian knock off of a Colchester lathe where the compound lock bears directly into the way side of the gib (yes, really, damages it too) has gibs scraped to that specific machine from the factory.

Chinese vendors have been implicated in "cosmetic" scraping too.
 








 
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