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[4]

Shim stock selection for gib shim on Bridgeport Mill

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tfleming

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#1
I need to shim the cross slide gib on my Bridgeport. Any hard and fast requirements as to whether to use High Carbon, Low Carbon, or stainless shim stock? I know to put the shim on the opposite side of the gib from where it contacts the way. So, since it is not on the sliding side of the gib, which type can I use or does it really matter?
 

cathead

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#2
If it isn't on a sliding surface, I can't see where it would make any difference as long as it filled the void. It's more important that the
shim is the proper thickness and fitted properly in my opinion.
 

T Bredehoft

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#3
I was advised that in a cast iron body, 1018 was a good material to use for a gib, it's innate lubricity would help. (it would slide nicely). If you're just going to shim it (isn't it adjustable?) it shouldn't matter what material you use.
 

Richard King 2

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#4
If the machine is worn, yes you can slide in a brass or steel shim back there. Plastic or turcite would be a bad choice as the clamp screw lock would squish those sorts. Ideally you would glue on a piece of Turcite on the wear side. If your not rebuilding the machine, sure shim on the back side.

I would suggest a brass shim and if it starts to move out saw a slot in the back of the gib just in front of the gib screw slot about 1/16 deep and bend the brass shim and insert the brass shim into the slot and bend it over, use a ball peen hammer to smooth out the shim at the bend.

If you use steel and ifit slides down it could scratch the cast iron, brass will wear and not the iron

Like I said, it's not ideal but many do it and it works.
 

machinejack

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#5
When I was working as a machine builder we would epoxy plain old kitchen formica on the back static side of the gibs after machining and hand scraped the ways in. Remington arms in Lonoke, Arkansas had tons of headers and presses that would need rebuilding kept us busy.
 

Richard King 2

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#6
We still use "grade linen"phenolic that was called years ago formica in he old days. I still use it on gibs on the wear side and on head and tailstock on thead grinders. Once I remember or figure out how to down load some pictures i can show it under the thread grinder stocks.
 

tfleming

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#7
Thanks guys. Yes, the shim will be on the "static" side of the gib, so there will be no moving involved or direct contact with the way. The only time the shim will move is when the gib is adjusted. . Right now my main intent is to get this machine into reasonable working condition. I don't have the budget to do a full fledged "grind and scrape", but then I also don't have to keep critically tight tolerances either with this machine. This is primarily to get the gib back into the cross slide so it does not protrude so far out the rear of the slide and interfere with the rear wiper when correctly adjusted.
 
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