Bud asked:
Can someone tell me how to drill small holes (for pots, 1/8-inch phone
jacks, RCA phono jacks, etc.) in typical small aluminum chassis (plural)
so that the holes aren't triangular?<
Firstly, start with a small pilot hole, and centre-pop the centre. Make sure
the drills are sharp. If you're skilled, you can sharpen a drill on a
grindstone by just holding it. I can't - I can't even guarantee getting it
right with biggish drills and various patent fixtures! Clamp the material down
on the work table of the drill, using some scrap wood as packing underneath the
metal. Don't use too high a speed - figure on about 60 feet/minute as the
peripheral speed of the drill. For very small drills (under 1/16th inch), this
generally means that you can't go fast enough. I don't generally use lubricant
on thin aluminium, but some people recommend it. I also find it useful to drill
undersize and use a taper reamer. Generally, triangular holes come about as the
result of 'chatter' when things aren't held firmly. Also, don't led the drill
take charge and try to 'walk' into the hole. This can be a real problem with
copper and brass, which is why it's recommended that you use d
rills with negative rake for those materials. I never bother, since I don't
drill enough brass (except in the lathe) to make it worthwhile.
73
Peter W6/G3RZP this week
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