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Old 9th Feb 2019, 7:47 pm   #1
Steve_Bell
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Default Using hole punches on die cast boxes

I am building a small valve amplifier and needs to punch 30mm holes in a die cast aluminium box. I have used the Q-max-type punches on sheet aluminium but just wondered if they work well on die cast?

I don't want to damage my expensive box. The box material is aluminium alloy ADC12 and wall thickness is 2mm.
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Old 9th Feb 2019, 8:15 pm   #2
G6Tanuki
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Default Re: Using hole punches on die cast boxes

I'd be reluctant to do it - the biggest hole I've ever free-punched in cast-alloy was for a RCA "Nuvistor" triode and that was only about 0.7 inch.

For 'holing' diecast where I can't specify the holes as part of the original casting, I've used "cone-cut" stepped borers, or when it comes to an 8x6 hole for a loudspeaker, drilling a load of 3mm holes. knocking-out the centre, then taking-out the rough edges with a rotary file.
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Old 9th Feb 2019, 8:46 pm   #3
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Default Re: Using hole punches on die cast boxes

Don't do it! The aluminium is guaranteed to crack.

Chain drilling and filing is the way to go.
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Old 9th Feb 2019, 8:53 pm   #4
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Default Re: Using hole punches on die cast boxes

Agree, don't do it, your chances of success are slim.

Use a hole saw, nice and slow with a bit of oil.

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Old 9th Feb 2019, 8:59 pm   #5
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Default Re: Using hole punches on die cast boxes

No don't chance a Q-Max type hole punch. They are excellent for soft metal but die-cast is hard and brittle. I tried it in my early days when I wanted to build a pre-selector for my shortwave radio when I was around 17. I needed a 3/4 hole for the slow-motion drive and drilled a pilot in the lid of the die-cast box (which would become the front), inserted the Q-Max and began to turn the screw barrel down....it started to cut and then there was a bang and a large chunk of the die-cast broke out...I had to wait another week to go to Home Radio and buy another.... I think a cone cutter or maybe one of those hole cutters you can fit to a drill will work. Failing that, a circle of smaller holes and then punch out the centre, finishing off with a rotary file
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Old 9th Feb 2019, 9:15 pm   #6
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Default Re: Using hole punches on die cast boxes

Well, I defer to the majority view expressed above- but I regularly used to use small and large Q-Max cutters on Eddystone die-cast boxes at work for one-offs and interface boxes. It tested the biceps on a long-arm Allen key- but the result was invariably a crisp hole without distorting, cracking or otherwise harming the box, though the waste punch-out was almost always cracked and sometimes crumbled.

This was with someone else paying for punches and Eddy-boxes though!- had it been my own stuff, I might (would) have been more hesitant. It's possible that other makes of die-cast box might not have been so forgiving or robust.

Maybe play it safe and go the somewhat longer route.
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Old 9th Feb 2019, 9:45 pm   #7
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Default Re: Using hole punches on die cast boxes

I've also tried this once at work & it did work OK producing a nice clean hole, the waste part ended in bits too.
The reason for not using a hole saw, well someone had borrowed the kit and returned it with the needed one missing of course.

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Old 9th Feb 2019, 9:47 pm   #8
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Default Re: Using hole punches on die cast boxes

In my experience, far and away the best tool for drilling sheet metal, diecast boxes and acrylic sheet is a 'step drill' also known as a 'cone drill'. They start their own pilot hole, don't snatch or grab, and are easy to use in a pillar drill (not a hand held electric drill). You just continue drilling one step at a time till you get to the desired sized hole. No dramas. EG. This one drills in thirteen steps from 5mm to 35mm:

https://www.amazon.co.uk/gp/offer-li...&condition=new

You can get more expensive ones, but as they tend not to get used too often, a cheap one is good enough for most requirements.

Hope that helps.
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Old 9th Feb 2019, 9:58 pm   #9
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Default Re: Using hole punches on die cast boxes

I have had good experience using "qmax" on diecast as well - I wouldnt want to go much above 30mm though, gets a bit demanding on the allen key
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Old 9th Feb 2019, 10:04 pm   #10
Steve_Bell
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Default Re: Using hole punches on die cast boxes

Thanks everyone for your replies. I will go the step/cone drill route, as I have one that will do 30mm.

I've just tried using a punch on a spare die cast box lid and it worked OK but I could see the lid deforming as I tightened the punch Allen screw. The punched-out circle was cracked into several pieces. I actually want to punch the holes in the box part, rather than a flat lid, and fear it might just crack or shatter under stress. At 20 for the box, I'll take the less risky option.

Last edited by Steve_Bell; 9th Feb 2019 at 10:12 pm.
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Old 9th Feb 2019, 10:25 pm   #11
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Default Re: Using hole punches on die cast boxes

I've never had a problem, and I also use a cone cut bit, especially in plastics. You need
to make a large hole for the bolt on an 85 mm cutter.

If you have a couple of thin pieces of ally scrap, use them both sides of the diecast box
wall this will reduce the risk of fracture. It is imperative that the bolt and cutter are
well lubricated.
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Old 9th Feb 2019, 10:39 pm   #12
60 oldjohn
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Default Re: Using hole punches on die cast boxes

Quote:
Originally Posted by David G4EBT View Post
In my experience, far and away the best tool for drilling sheet metal, diecast boxes and acrylic sheet is a 'step drill' also known as a 'cone drill'. They start their own pilot hole, don't snatch or grab, and are easy to use in a pillar drill (not a hand held electric drill). You just continue drilling one step at a time till you get to the desired sized hole. No dramas. EG. This one drills in thirteen steps from 5mm to 35mm:

https://www.amazon.co.uk/gp/offer-li...&condition=new

You can get more expensive ones, but as they tend not to get used too often, a cheap one is good enough for most requirements.

Hope that helps.

Another vote for cone drill, take it easy as you go. Mine quite surprised me, I had 18 holes in 6mm steel to drill 25mm diameter. I managed real easy with no signs of blunting.


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Old 9th Feb 2019, 10:59 pm   #13
M0FYA Andy
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Default Re: Using hole punches on die cast boxes

I've used hole saws on diecast boxes with great success.

Andy
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Old 10th Feb 2019, 12:39 am   #14
Restoration73
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Default Re: Using hole punches on die cast boxes

Step drill is not the same as a conecut bit - I have used the latter in a hand drill but for
plastic and ally but a slow drill speed is needed.

https://www.kelvinpowertools.com/con...-c-443-p-10890
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Old 10th Feb 2019, 1:01 am   #15
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Default Re: Using hole punches on die cast boxes

I've got both step and cone drills but will use the step. I have a bench drill press, so better control than a hand-held.
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Old 10th Feb 2019, 7:41 am   #16
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Default Re: Using hole punches on die cast boxes

If you are going to use a cone or step drill, make sure it is in a drill press with the work clamped. Or if you start of from a small diameter initially and enlarge it over multiple steps, the hole center will wander.

However, if you file out the hole to within a mm or two of the size you want, on the correct center, then with the stepped drill, it will be pretty close to accurate centering after only one step to enlarge it, even if the work is not clamped. The cumulative centering errors add up if it is not clamped and you start from a small hole.
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Old 10th Feb 2019, 10:28 am   #17
60 oldjohn
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Default Re: Using hole punches on die cast boxes

Quote:
Originally Posted by Restoration73 View Post
Step drill is not the same as a conecut bit - I have used the latter in a hand drill but for
plastic and ally but a slow drill speed is needed.

https://www.kelvinpowertools.com/con...-c-443-p-10890

OOPS, My mistake, I have both and I know the difference. I agree with every word above. Step drill cutting progressive steps should not wander.


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Old 10th Feb 2019, 11:13 am   #18
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Default Re: Using hole punches on die cast boxes

Step drills tend to leave a ridge from the next layer up so drilling the last bit out from the other side can provide a cleaner hole. With cone cuts the hole has a bevel on it too. Also, be very aware of snagging and snatching which can be painful if cutting with a handheld drill. I tend to use the slip clutch on the drill if there is a risk of this happening. If you can secure the work in a vice or clamp better still. All from bitter experience...I should have known better.
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Old 10th Feb 2019, 11:18 am   #19
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Default Re: Using hole punches on die cast boxes

I`ve never had a problem using Q-max type cutters on die cast boxes but step drills also work well - I don't much like conecuts as they seem to require inordinate pressure to work.

If you don`t already have a Q-max step a stepdrill may be cheaper - I picked up a couple in Lidl a little while ago for next to nothing.
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Old 10th Feb 2019, 12:04 pm   #20
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Default Re: Using hole punches on die cast boxes

It is not unknown for step and cone drills to be seen on sale in Aldi too at an equally competitive price as Lidl do them for.
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