** I find using a Hall step drill with 1mm steps works very well with plastic and die cast alloy boxes. Particularly good with 19mm holes for male XLR connectors.
With a drill press it goes through so smoothly one can safely hold the box by hand.
.... Phil
Let me clarify. "It's the cutting angles, not the sharpness, that cracks your acrylic".
Sometimes a blunt drill is less likely to crack brittle plastics because of the heat it generates on the way through.
In acrylic, that can only reduce the scale of the cracking.
Yes. Or re-grind your own. This page has instructions:
Clifford Heath.
Thanks for all the suggestions, folks. I happened to have a step bit on hand, so I tried using that with a hand drill and a starter hole and it worked great.
I think part of the reason is the step bill has a tapered cutting surface on each step, so during the cutting process it leaves more material in place which leaves the box edge stronger and less prone to cracking during the cutting process. It still requires a bit of care to get right, so I practiced on a test piece first.
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On Fri, 13 May 2016 08:32:13 -0400 (EDT), bitrex Gave us:
Best way for drilling plastic, since it is usually so soft (relatively) is to use a very tiny bit to location the hole and make a perpendicular initial drilling.. Then use the size you want to finish with.
There are also "plastic drill bit" specifically for plastic. Some are single flute, others not, but they make clean shafted holes, whereas a regular dual fluted bit typically will not or will make egg shaped anomalies along the shaft path. (shaft meaning 'drilled hole').
Also slow rpm and feed rates work well, but one has to experiment with a given polymer to see what works best.
On Fri, 13 May 2016 08:32:13 -0400 (EDT), bitrex Gave us:
Put a block of wood behind thin cross sections and the resulting hole will be cleaner. Traverse "through the breach" slowly and carefully. (the breach being the moment when you break through).
Have you found a good place to buy those? Most results I found were rather expensive.
With small 1mm steps, it's almost like a reamer, which should work. I've had failures with step drills that have more radical steps.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
On sale now at $14 for 3 drills.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Am 12.05.2016 um 22:59 schrieb bitrex:
...every time the bit cuts through...
Reminds me that there are two types of cut in most drill bits. In the center, the drill bit pushes material to the sides due to the slow speed. On the outside, the cutting edge scrapes the material.
The center needs about 2/3 the force needed to push in the drill bit. If the drill bit pushes through, the force has to be reduced immediately. Otherwise, something will break: the drill bit, the lip of mertial,...
cheers Gunther
laser cutter if you can.
Else: lip-and-spur bit, slower feed rate, higher spin rate. if the bit tends to grab wobble the drill a bit to reduce the binding (do this early)
-- \_(?)_
I should have said that I meant the G&J Hall brand ones, in the 1mm increments, e.g. MC3M, which is $182.50 / GBP62.55 from element14!
I already have a bunch of cheap ones with 2mm steps.
Chris
** IIRC, I bought my 10-20mm GJ Hall step drill from Farnell in 1997 for A$40.
Made by hard working pommy gents in Sheffield, for the industrial & commercial tool market.
( Not Chinese flunkies in " Hoo Fung Dung" working for a bowl of rice a day )
Racism fully intended .....
.... Phil
$98.11 on this side of the pond. More:
The step drill on the left in the Harbor Freight web page goes in
1/32" (0.794mm) increments. That would be a smaller increment than your current 1mm flavor. I don't know if a smaller step is considered a sign of better quality. Harbor Freight is usually junk, but I've had good luck with these drills, except when drilling plastic, which judging from the good reports from others, I must be doing something wrong.-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
That's a 20-30mm step drill- huge with a small step size and large minimum size. Interesting that I see the US price as $98 from Newark/Element14. Plus $20 to get it from the UK to US.
If 4-12mm in 1mm steps is big enough, they're $20 at M-C (or $27 if you want TiN (nitride) coating).
--sp
-- Best regards, Spehro Pefhany Amazon link for AoE 3rd Edition: http://tinyurl.com/ntrpwu8
Thanks, that one is A$120 now. I guess it's just price inflation then.
If you're still using it now then that is a good sign.
The 1mm step requirement is not so much a sign of quality, more that if you have a 25mm cable gland to install, then a 24mm hole is too small and a 26mm hole is a bit too big, especially if they drill slightly oversize. The 1/32 step would be better than a 2mm step in this case, but not ideal.
** Yep, just the other day for fitting a fuse holder in 1.2mm steel, reckon I've had my $40 worth of use many times over.
For holes larger than 20mm up to 35mm, I use Q-max chassis punches and doing that is often seriously hard work.
.... Phil
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