Bridgeport or Knee Mill, VMC, Surface Grinder Owners.

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Richard King 2

Master Machine Tool Rebuilder & Instructor
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Bridgeport or Knee Mill, VMC, Surface Grinder Owners.

Here is a tip for you. In all my 50+ years of Rebuilding Machines 99% of used Knee mill machines the table is bowed up in the middle. Or the Mill tables is bent convex averaged .006" If you had a straight-edge and set it on a stoned table it will pivot in the middle. I used to think that was because the table is longer then the saddle and over time it bends.

I was partially right, but I met a Engineering Professor named Archie Cheba (spelling may be wrong) who told me the main reason is when the operator tightened the vise on the table over time the T-slot iron gets stretched or peened. So this tip is to buy or make longer 3" T-Nuts then the average T-Nut that is about 1" long. Also move the vise from side to side and not always in the middle.

You can also do this on machining centers and grinders, don't always set small parts in the middle of your table. It wears more evenly.
 
I had an old #2 B&S universal mill from about 1906 that had a .019 convexity on the table top, finally had a rebuilder on Berkley regrind it and install tef/bronze in the saddle, used it for many years until a somewhat more modern one came along, a 1940s model.
 
Richard King 2 said:
Bridgeport or Knee Mill, VMC, Surface Grinder Owners.

Here is a tip for you. In all my 50+ years of Rebuilding Machines 99% of used Knee mill machines the table is bowed up in the middle. Or the Mill tables is bent convex averaged .006" If you had a straight-edge and set it on a stoned table it will pivot in the middle. I used to think that was because the table is longer then the saddle and over time it bends.

I was partially right, but I met a Engineering Professor named Archie Cheba (spelling may be wrong) who told me the main reason is when the operator tightened the vise on the table over time the T-slot iron gets stretched or peened. So this tip is to buy or make longer 3" T-Nuts then the average T-Nut that is about 1" long. Also move the vise from side to side and not always in the middle.

You can also do this on machining centers and grinders, don't always set small parts in the middle of your table. It wears more evenly.
Click to expand...

Richard King 2 said:
That's why you should move the vise away from the middle of the table from time to time. :cool:
Click to expand...
This is really good advise. Something I never really gave any thought to.
 
Interesting problem but I don't think longer tee nuts will make a difference. The pressure from the screw will not be effectively transferred to the ends of a longer nut. Probably not even 100% pressure dispersion getting out to the ends of the 1"nuts, either.
 
yea, none of my mill tables are perfect...

That's why I REALLY LIKE soft jaws in the mill vice. make one skin cut every time the vise is installed. Now you got a vise with perfect tram and level. Quick'n'easy
 
Eddyde said:
Interesting problem but I don't think longer tee nuts will make a difference. The pressure from the screw will not be effectively transferred to the ends of a longer nut. Probably not even 100% pressure dispersion getting out to the ends of the 1"nuts, either.
Click to expand...
The Professor told me longer would do it. He said his friend did a "paper" on it. He knew and didn't "think" about it. I have been telling people that info for years and no one has told me it didn't work.
 
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