we drill LOTS of holes in composites at the day job, couple of things that can help,
1) step your way up to the final size, for 1/2 inch I would drill a 3/8 to start, followed by 7/16 then 1/2inch (see note 6), high speed low force WATER!
2) ALWAYS back up the hole, pvc pipe or wood can work well
3) carbide tools
4) drill them wet, dip the drill bit in water before AND after drilling the holes, lubricates and cools
5) use a drill press or an 'egg cup' if you can to hold the drill straight
6) use a dreamer (drill reamer) or dagger drill for the final cut, not a twist drill
7) if you have to use a twist drill, use one for composite 120 or greater angle, multiple flute, don't use brad point unless you have everything held VERY rigid
For larger holes use a grit hole saw and an arbor (3/4 or bigger)
Mike K
(composite manufacturing is the day job)
For holes that large, take a look at 'step drill bits'. A good one works well. It's how I drill 1/2" holes for Schurter switches.
ok I know it may have been posted already but whats the best way to drill a 1/2" and a 5/8" hole in G12 fiberglass tube. its for my switches
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