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Old January 27, 2014, 10:09 PM   #10
Dixie Gunsmithing
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Join Date: April 27, 2013
Location: Ohio
Posts: 1,923
The bolt lugs on some bolts were actually milled on a horizontal mill, using a cutter with the partly round profile of the bolt, then it stopped off to leave the lugs. The bolt face was turned to the outside diameter of the lugs, and the profile cutter milled the top and bottom, leaving the two lugs.

The receiver is generally broached in a hydraulic broach, where it pulls a long toothed carbide cutter of the profile through the receiver, out the front, and cuts the two recesses that match the lugs. Each tooth cuts about .005+" each, which steadily get larger, and a long row on each side of the broach cuts both recesses in one pass. This is the same way keyseats are cut in gears and sprockets.

Another way is to use a shaper, with a rotary indexer holding the frame. The broach is much faster by far.

The inside face of the frames lugs can be milled several ways, including a boring bar in a mill.

I forgot to add this on tapered cam surfaces. Cincinnatti, and a few makers of large vertical mills, had a setup that had a rotary table sitting on the longitudinal table. It's rotary motion was connected to a gearbox, and then onto the table feed. They used this to cut some forms of worms, and also tapered cam surfaces on ID's and OD's of round objects and faces too.

Last edited by Dixie Gunsmithing; January 27, 2014 at 10:48 PM.
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