Odd knee gib arrangement in 6x26

T

tcooper27

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Hi all,

I just picked up a Select OB 6x26 mill and came across this gib setup in the knee when cleaning everything out. Only the top portion of this is tapered and scraped in, the rectangle aluminum just takes up space below it. There’s adjusting screws top and bottom. Is this a normal arrangement or something weird? I can tell the top part came with the machine originally, it is stamped 0103 like many of the other parts of the mill.

I ordered a replacement gib from Grizzly’s g0729 hoping it would fit but it’s a different taper. Old gib seems to be .0075 per inch and the gib from the Grizzly is .01 per inch.


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One should expect to have to scrape in a replacement gib for any machine tool.
 
It's possible the original gib broke and the previous owner stuffed a spacer in
If the gib is much shorter than the space it fits into that's very likely what happened
 
markba633csi said:
It's possible the original gib broke and the previous owner stuffed a spacer in
If the gib is much shorter than the space it fits into that's very likely what happened
Click to expand...
Yep. It wouldn’t even be a little bit surprising.

Picture it. Dude is running the machine, and notices the gib is sticking out. He tugs on it, pulling out the broken half. Weird..he thinks. Oh hey, it’s break time. He sets it on the knee ways. While he’s taking an overly long break, the boss tells some other guy to finish up that part. Cause Jesus Christ that part is HOT! We need it yesterday!! The new dude picks up the broken gib, doesn’t recognize it, and chucks it in the scrap tub.
A few days later, the dude who originally pulled out the broken gib has to use the machine again. He notices the damn thing is acting crazy. Then he remembers he’d pulled out some shim or something the other day before break. It’s gone, so he strolls over to the stock rack and eyeballs a piece of aluminum that looks like it’ll fit. Jams it in the gap, and back to making chips.

The end
 
Yeah that sounds like a likely scenario. The gib is only about half the height of the knee so I’d like to replace it to get it bearing on the full length.

The new gib from Grizzly looks right except the difference in taper amounts to it being about 0.02 too thin on the thin end. The big end is the correct size. I see that shimming gibs is common but can I just shim one side to adjust the taper? Or should I just try to make a new one?
 
tcooper27 said:
The big end is the correct size. I see that shimming gibs is common but can I just shim one side to adjust the taper? Or should I just try to make a new one?
Click to expand...
If you have the ability to make it correctly, and the interest in doing the work, you may want to remake it.

I think I would try out the Grizzly gib, and evaluate.

I mean you’re gonna have to have something in there to make a replacement anyways.
 
It probably came that way from the factory, did it work okay as it was?

When I bought my lathe it was missing one of the gibs. I bought one from Grizzly and trimmed it to fit. I did not scrape it in but fortunately the seller found the missing gib and got it to me.

If this machine were mine I’d be tempted to put it back together and evaluate if the spacer seems to be causing a problem. What you don’t know is how well the dovetail is made and if you’ll cause a bigger headache trying to fix this “problem”.

I’m guessing the Select is an economy Taiwan or Chinese mill. Sometimes funny things happen in the factory and they just do what’s needed to get the machine out the door.

What really matters is if the machine can make parts within acceptable accuracy for you. Might be a case of letting sleeping dogs lie.

John
 
Try to fit the one you have, you can probably get it to work at least temporarily.
You can put some sharpie pen ink on it and see where it's making contact- trim the length if necessary
It would be ok to use a short spacer also like an inch or two- this is prototyping after all
 
It is an Taiwan import, made in '77. Overall it is in pretty good shape and all the original hand scraping on the gibs and ways are still present so I don't think it was abused too much.

I'll put everything back together as-is and see if it works right. If it does then I'll probably leave it alone as you guys suggest. My only concern then would be it's wearing on a 4" section of the dovetail when it could be spread out over the full 8.5". There's no fine feed on the quill on this mill so I'll be using the knee relatively more. Then again I'm just a hobby guy so maybe that's no big deal.

I saw another post about flowing solder under the fixed side of the gib with one end shimmed up the proper amount to adjust the taper followed up by scraping everything flat. I might give that a go with the Grizzly gib I bought at some point.
 
I have some scraping tools but haven’t really tried it yet. Seems fairly involved, maybe a project for after I retire.

I put a thin strip of plastic behind my Grizzly gib and it seemed to work well enough.

My tools are older Taiwan built too. I believe they are more accurate than I am :grin:

John
 
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