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Author Topic: Drilling holes in sheet metal  (Read 28648 times)
N2EY
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Posts: 3913




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« Reply #15 on: February 15, 2012, 03:35:12 PM »

Here's what I do:

First I scribe a half-inch circle.

Then I drill a small hole in the exact center.

Then I enlarge the hole to 3/8 inch, since I have bits and a drill up to that size.

Then I enlarge the hole using a coarse round or half-round file. Aluminum is soft and files well. From 3/8 to 1/2 is only 1/16 of an inch all the way around. Filing to the scribe line is easy.

For bigger holes I use a different method, a nibbler or a punch.

73 de Jim, N2EY
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KC2RLY
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Posts: 37




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« Reply #16 on: February 16, 2012, 03:24:40 AM »

use a hole saw, attach the work to a sacrificial board, spray it with wd-40 while cutting, go slow, hole will be perfect and the saws will last a life time.
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K0IZ
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Posts: 739




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« Reply #17 on: February 16, 2012, 05:23:34 AM »

Two more suggestions:  (1) drill a 3/8 hole.  Use a tapered wood rasp (type with 1/4 shaft for drill or drill press) to enlarge hole.  When getting close to final size, continue to expand from both sides to reduce the taper of the hole sides. (2) use a hand reamer, most go to 1/2 size.
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KB1GMX
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Posts: 815




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« Reply #18 on: February 16, 2012, 03:08:15 PM »

an example of a cheap drill press.

Harbor freight Item # 38119  currently on sale for $69.

You can spend more... but that will do for most work.

Basic tool and the user set speeds are like many with three or five steps on the
drive pullies at the top for basic drill speeds.

That and a drill press vise to hold the work, a drill bit set and a few different size unibits
and your good.

Dremel is small, and very high speed, good for drilling PC boards and holes under
maybe 1/16th inch.


Allison
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KB1WSY
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Posts: 813




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« Reply #19 on: February 16, 2012, 03:15:57 PM »

>>Harbor freight Item # 38119  currently on sale for $69.<<

Wow, that's a really nice drill press. Haven't done this kind of thing for decades and didn't realize how affordable these sorts of tools are nowadays.

Martin
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NO6L
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Posts: 179




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« Reply #20 on: February 17, 2012, 02:48:55 AM »

I didn't 'miss' holesaws, I just wouldn't even consider using one for drilling a 1/2'' hole in aluminum. A step drill will do the job quicker and easier plus produce a cleaner hole, especially with a hand drill.

Please forgive my intrusion upon your thread. Also, please forgive me for being so presumptuous to think that maybe there are other sizes of holes someone may wish to cut. Oh, wait, it wasn't your thread in the first place. And you are not the only one here, I guess I'll retract my request for forgiveness.

Have a nice day, either way and 73.
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NO6L
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Posts: 179




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« Reply #21 on: February 17, 2012, 03:09:49 AM »

use a hole saw, attach the work to a sacrificial board, spray it with wd-40 while cutting, go slow, hole will be perfect and the saws will last a life time.


Something to consider. You generally don't use a lubricant with soft non-ferris metals like aluminum, just cut dry at a reasonable speed for the size of the saw. Up to 1" would be about 800 rpm. A rule of thumb would be reduce speed by half when doubling the size of the saw. If you're cutting steel, use machining oil and reduce speed by half or more and only use enough pressure to avoid more than a wisp of smoke from the work. If in doubt, cut at a lower speed, you just won't get done as fast and it'll be safer.

73
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KK0G
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Posts: 48


WWW

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« Reply #22 on: February 17, 2012, 12:56:28 PM »

I didn't 'miss' holesaws, I just wouldn't even consider using one for drilling a 1/2'' hole in aluminum. A step drill will do the job quicker and easier plus produce a cleaner hole, especially with a hand drill.

Please forgive my intrusion upon your thread. Also, please forgive me for being so presumptuous to think that maybe there are other sizes of holes someone may wish to cut. Oh, wait, it wasn't your thread in the first place. And you are not the only one here, I guess I'll retract my request for forgiveness.

Have a nice day, either way and 73.

The poster didn't ask about drilling other sized holes, he asked about drilling 1/2" holes in sheet aluminum. He could also use a plasma cutter, an end mill, a single point bit in a lathe or even a .50 caliber rifle to make 1/2" holes in sheet aluminum but I'd probably still recommend a step drill.
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AA4PB
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Posts: 12987




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« Reply #23 on: February 17, 2012, 01:27:58 PM »

A step drill will work but you've got to make sure the sheet metal is supported really well (depending on its thickness). If the step drill catches it will bend the metal and you'll have a really ugly hole. A 1/2 inch Greenlee punch can be had for about $40. That would be the very best way to go and then you'd have it for next time. Back in the day when we were mounting tube sockets into a metal chassis that is what we always used - although they were a lot less expensive in those days.
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G3RZP
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Posts: 4845




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« Reply #24 on: February 18, 2012, 03:36:12 AM »

All the older books recommend a lubricant for drilling aluminium, usually turpentine. I wouldn't know where to get genuine turpentine these days - all i see over here is 'turpentine substitute' which is not the same.

But the variety of answers shows that there are more ways of acheiving holes in sheet metal than you might think.
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KB1GMX
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Posts: 815




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« Reply #25 on: February 19, 2012, 03:45:11 PM »

Myself I use a product called Koolstick.  Kerosene (paraffin) and have in the field used a conventional wax candle.

I've use Greenlee Dies for holes and they work but you still need the pilot hole.
hole saws must be good ones to get decent holes, cheap ones don't do it, run
them slow and use a drill press.  I've also use flycutters  but with great care and
generally for thicker materials, drill press or a mill and clamped work is a must for that..

The original request about using a modified spade bit would work too.  However, its'
right up there with the flycutter.  If it grabs and the work isn't secure the work may
spin or the hole will tear.  If the work spins it could cause injury.

The problem with using .50cal is the burr on the backside.  That and about $2.00 a shot. Wink


Allison

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G3RZP
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Posts: 4845




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« Reply #26 on: February 20, 2012, 03:40:59 AM »

I agree with Alison - the work needs clamping. Another technique, if it is physically possible - it isn't always - is to drill from one side until it not quite breaks through, then turn over and drill from the other side. This gives a cleaner hole.

Haven't met using a candle - here, the electricity supply seems to get more and more unreliable, and candles are in great demand in this house!  12 hours off just before Christmas, then they brought an emergency generator for 10 days, then 2 hours off after they took that away and restored supply, 7 hours off last night. Getting to be like one of these West African countries! Losing power in the workshop can be very dangerous as the lights go out but the machines are running down.
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WD4HXG
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Posts: 186




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« Reply #27 on: February 20, 2012, 02:50:10 PM »

Before the advent of the Unibit I used regular
Jobber bits, drilling smaller holes then incrementing
up to the desired hole size. For 1/2 inch I would
start with a 1/4 inch bit and then increment up
using indexed sizes of 1/32 until reaching 1/2
inch. Use a relatively slow speed on you drill
press. If you have to use a hand drill then let
the bit do the cutting and do not press down on
the drill motor.

An added advantage can be had by using an
impact punch to make a center relief to guide
the bit on initial contact. It will go a long ways
to keeping the hole well centered and if you
index up on the hole drilling with incremental bits
till you have the right diameter hole you will have
nice circular holes.

73

Chuck WD4HXG
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KC2RLY
Member

Posts: 37




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« Reply #28 on: February 21, 2012, 10:34:52 AM »

All the older books recommend a lubricant for drilling aluminium,

thank you
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WD4MTW
Member

Posts: 62




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« Reply #29 on: February 22, 2012, 10:20:34 PM »

If you're going to do a lot of chassis working and need to punch holes larger then a step drill, you might want to look into Harbor Freight's hydraulic punch set. When it's on sale and you can use a coupon code, the price is about $70 that includes punches from 3/4 to 2". The have some larger ones available occasionally in sizes up to 3" at extra cost. It's a bargain as it goes through steel stock easily with several pumps. It looks identical to the Greenlee or Ridgid sets, but a fraction of the price. The purchase of a few small Greenlee punches would pay for one of these.
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