Work Holding

[daveb56]

I have a project of drilling three 2.00" holes in 4 X 5 rectangular tubing . The tubes are 99 inches long the holes are 47.5 inches apart. Tolerance are .010 on location. I have 60 inches of travel so two set ups are a must. I could have up to 2 thousand to do. I am looking for ideas on a quick & solid work holding fixture . This is a horizontal mill with two large angle plates. I am leaning toward two air vises. I don't know if they will hold with no part movement. Any input to this would be appreciated.

Thanks daveb56

[RICHARD ZASTROW]

Dave, Air vises should hold the pieces without movement.

Personally I'd make a drill fixture and drill the holes with a magnetic based portable drill and a "slugger" or "roto-bore" tool. Might be a little more complicated if the holes go thru both sides of the tubes. Might require the fixture to pilot a longer tool. Can be done, I believe.

Dick Z

[DareBee]

Similar to RICHARD, I would use a Roto-Brute cutter.
I would set up a jig on a mill table (preferably a long one).

The jig would have a 1.995 pin on it at exactly 47.5 from the spindle.
End stop for the first hole. 1st hole on the pin for the 2nd hole. 2nd hole on the pin for the 3rd hole.
NO clamping or table movement would be involved.