How to use clamping kit on Atlas mill table

JPMacG

JPMacG

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I am using a clamping kit to hold work down to the table of my Atlas mill. By clamping kit I mean the usual kit that includes studs, flange nuts, Tee nuts and serrated blocks. I worry that if I tighten the nuts too much I might risk breaking out the table T slot.

What is the proper way to use one of these kits? Should I be compressing the T slot and not pulling up on the T slot? How would I do that?
 
On the better-quality kits, the threads of the T-nuts are swaged at the bottom. This prevents the studs from passing through the T-nut and breaking out the T-slot as you tighten the clamps down.
 
That’s an interesting question. Never in all my years have I had that concern. I suppose it could happen, but I have never seen nor heard of that kinda damage to the mill table. However, on a similar note. When I got my second hand Bridgeport mill. I notice that the previous own(s) over tightened or used the wrong size “T” nuts and this caused a very nasty burr in the slot. This burr was so bad that I could not use guide pins or blocks in the 5/8” slot. I had to make a filling jig to carefully remove the burr. It’s all good now….Dave

Correction: I was only thinking milling table. I have seen many times, the “T” slot in a lathe compound or “T” slots in micro machines damaged/ ripped apart.
 
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Typical use of the clamps will always have an upward force applied to the Tee nut and thus the casting immediately surrounding the Tee nut. It is conceivable that over-tightening the clamp could induce a fracture in the table. Without a specification for the table casting, it would be difficult to put a number on the proper torque. An improperly cut slot or the wrong size Tee nut could result in higher stresses on the casting.

After multiple decades, I have never had an incident with the clamps and I tend to be fairly aggressive when clamping. I would suggest starting out clamping with the minimum force required to secure the work. After a while you will get a feel for what is needed. Clamping should be done at three points, not in a line, if possible. This will reduce the amount of clamping force needed to properly secure the work.
 
VSAncona said:
On the better-quality kits, the threads of the T-nuts are swaged at the bottom. This prevents the studs from passing through the T-nut and breaking out the T-slot as you tighten the clamps down.
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You can do that by taking a punch to the bottom of the tnut, put it in a vise upside down, then use the punch on the edge of the thread bottom and put a couple of dimples in the threads, it will make the thread stop
 
Where possible I try to secure the work to the table by putting everything in compression rather than putting the T-nut slots in tension in the conventional way. This is done by bolting through the work where possible.
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This is not always possible of course, but I keep the T-nuts as close to the work as possible to try to minimize the tension on the T-slot.
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Thanks everyone. When I purchased my MFC several years ago I got a basket of extra MFC parts along with the good mill. Among the parts was a table with a broken out slot. I don't know how it happened, but I want to be sure that I don't do the same to my good table. It sounds like there should not a problem as long as I don't use my 24 inch breaker bar on it.
 
Also, it's a good practice to keep the stud as as close to the work to maximize the clamping force. The force applied by the stud is divided between the work and the step block, the ratio being the ratio of their respective distances from the stud.
 
Don't use a bolt in a T-Nut without confirming that the bolt isn't too long. And to repeat what was written back up the thread, don't let the stud run through the nut.
 
if you want to make sure your part doesn't move put a piece of paper under the part you are clamping the abrasiveness of the paper will help stop the part from turning or moving. then just tighten normally with a standard length wrench . bill
 
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