I tried milling the recesses with a 3/8" end mill without success. The Sherline lacks the power to cut steel, even at .001 inches per minute. So I tried to create them with a .390" drill in the drill press. I had to work my way up from .25" and still I am sure ruined several drill bits. The end of the bit glowing red is a giveaway
Eventually I put a 3/8" end mill in the drill press at 200 rpm. This did the job, but not well. An end mill is held by a set screw in a holder. A drill press chuck just isn't that effective at holding it. (Someone must make an end mill holder for use in a drill press chuck. What is it called?) In addition, my 3/8" square end mill is double ended and will not fit into the drill press's chuck, so I used a ball 3/8" end mill. Not a flat bottom, but should work okay.
Next time, aluminum, even if I have to cut it down from a much larger diameter.
Fortunately, I have enough 1/4"-20 x 1" Allen head bolts that will mate to nuts on the underside of the conveyance..
A squirt/spray bottle of coolant would help. Usually, if it turns red, you are spinning it too fast, and/or not feeding it fast enough. Lots of heat generated from dragging it around in shallow cuts.
ReplyDeleteA hex drive end works best, otherwise, use the biggest round drive end for a drill or milling bit that your machine can grab. Trying to use a stepdown drive end is a study in frustration, unless it is a hex.
Generally, attempts to run milling bits in drillpresses are problematic due to loose bearings in the head. Any play sets up a chatter, which tends to cause the bit to spin in the chuck, besides the very rough finish and lack of precision. Upgrading the bearings may be feasible.
If I understand you correctly, what you need is a counterbore. It's like a countersink, but sized to bore the clearance for the head of a given sized allen bolt.
ReplyDeleteWill: Used coolant, but speed was probably the issue. The end mill worked well at 200 rpm.
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