Author Topic: Raising and lowering the milling table with electric drill  (Read 3510 times)

Offline kvom

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Raising and lowering the milling table with electric drill
« on: August 21, 2009, 03:13:47 PM »
I made two recent changes to the Bridgeport mill tooling that have made frequent raising and lowering of the table a necessity.  The first is a keyless chuck that is quite a bit longer than the small chuck I used for center drills and the like.  The second is the rotary table-lathe chuck combo that is 10" or more high.

I had seen a commercial version of this tool for sale on the internet, but it seemed to be makeable inb the shop now that I had a rotab.



The "secret" to cutting the lugs is to realize that one side of each lines up with a side of the other with the line passing via the center.  So I took a 3" long piece of 12L14 2" rod, drilled a 1/2" center hole on the late 1.25" deep, and then used a 5/8 end mill to enlarge the hole to match the shank on the knee.  With the work held vertically  in the rotab and a 3/16" endmill in the spindle, I set the y-axis off center by half the diameter of the endmill.  Then it was a matter of making nine passes along the x-axis, each pass being 40 degrees of rotation, to form the 9 lugs.  The slots on the mill are .150" deep, and I made 4 trips around taking .04" DOC each time.

Afterwards I put the piece in the lathe and turned the opposite end to a .5" diameter for a length of .75", allowing it to be chucked in a 1/2" electric drill.  The lugs are a tight fit, but the tool works as it should.  I think offsetting the y-axis a few thousands extra would make the lugs a bit narrower and a looser fit.

Anyway, I'm happy with the result.  It took me about 2 hours to make.  I might have been able to mill the slots faster, but I wasn't sure how deep a cut I could take with that small endmill.