Cutting neat holes in anodized aluminum

[JammyBStard]

I'm building a couple of valve pre-amps in extruded aluminum enclosures like these:

I'm trying to make them look really nice as well as sound really nice. A few of my previous efforts are a bit too industrial looking for my better half.

So one thing I dont want to do with these is have the valve sockets mounted directly into the aluminum. Instead I want to slide a card of Tufnol into the enclosure on the runners below and mount the valve holders and turrets into that and have the top of the valves poking through neat holes in the aluminum. Like the Pro-ject tubebox but without the up-stands and rings around the valve.

An externally hosted image should be here but it was not working when we last tested it.

What do the experienced builders her think is the neatest way of cutting/drilling a hole in the aluminum without making a mess?
I was thinking step cutter perhaps? but they can be nasty and make a mess if they bite into the wall of the cut.

 

[bwaslo]

Greenlee (Q-max in UK) knockout punches. Check ebay, not horribly expensive.

 

[mcandmar]

Do they cut cleanly in thin aluminum or do they warp the panel in the process?

Up to now i've used those xmas tree stepped bits in a pillar drill as i found them vastly better than regular drill bits, but they still aren't perfect.

 

[nezbleu]

I have used the stepped drill bits as well, but always have to deburr and dress the hole with files to make it look decent. Punched holes are better but I'm sure you need to support the work properly to avoid warping. I don't know how thick of a panel you can punch with typical home tools.

 

[nezbleu]

One could always fit some sort of a grommet to cover the raw metal edge.

 

[bwaslo]

The Greenlee or Qmax punches punch the metal between the bit and a thick rigid cylindrical steel cup -- no warping. They've been the gold standard for thin aluminum radio chassis for about the past 80 years...

 

[JMFahey]

The greenlee punches mentioned above do cut cleanly through aluminum, doubly so because you are not cutting soft, thin, rolled sheet aluminum where they *might* but thicker extruded aluminum, which has a different alloy composition, is more rigid and which is cleaner cutting, has sharper defined edges.

 

[Sprags]

I would just program my DMG MORI Lasertec 65 to laser cut the holes. The problem with laser depending on how thick the material is reflash or the melted material that reattaches to the base material before its cooled and hardened. The edge gets better when you cut in an sealed chamber flooded with inert gas. OK...not really my machine but I could use it if I really wanted to at my place of business.

If it were just me I'd cut very carefully using a grinding bit and a Dremel. I have steady hand so I could get it the hole so round you'd think it was machine cut.

 

[JMFahey]

Well, if you accept sending it somewhere else, XYZ CNC milling machines, even small hobby type ones can do an excellent job.

A friend of mine makes excellent custom microphone preamps for Recording Studios (such as clones of old Neve/Switchcraft/etc.) , he bought one such machine which has a tiny worktable, say 2 printer sheets side by side, and he does *everything* on them, from XLR connector holes, rectangular ones for switches, slots for slider pots, screw and LED holes, windows for digital displays or needle VU meters, the works.
It's slow ... who cares? ... it can be left working while he does something else.
He cuts all holes, has the panel anodized, then cuts lettering and graphics so they stand engraved silver on a black or coloured background or he fills them with coloured wax crayons.

Very tasty.

Not telling you to buy such a machine (although they are not expensive) but find somebody close who owns one.

 

[heinz1964]

Hole saw

Hi

What about just using a hole saw. The ones we use for wood or electricians use for walls. They come in many different diameters and I think they can cut aluminium. You might have to smoothen the edges after. But you will have a round hole for starters.

best regards
uwe

 

[JonSnell Electronic]

Q max cutters are available from RS Components and Farnell etc. They are the industry standard for those without a Fly Press. They come in all sizes, here is an example of a hydraulic type. there are manual ones as well. Have a look;
| 35mm Hydraulic Circular Punch & Die Combinations |

 

[JammyBStard]

Thanks for all the help so far.
If I had a pedestal drill I'd probably have used a step cutter or good quality hole saw by now.
I use them both at work for cutting cable gland holes in columns from time to time. But I know with a hand drill they rarely make a neat hole.
My plan B is to use a silicone or PTFE grommet to hide any mess but I'd rather go for neat first.
I was also looking to see if I could find any sort of metal fanged sleeve that i could press into the holes once drilled but I've not had much luck with that either.

I think the best bet will be to try one of these 24mm Q.Max Sheet Metal cutters first and see if it can do the job.
There quite easy to get hold of on Amazon and eBay:
Just to check, is this the type of cutter suggested: Q.Max Sheet Metal Punch 24mm | eBay

 

[jacco vermeulen]

Lubricate & cool, aluminum is soft and sticky.

 

[JammyBStard]

Lubricate & cool, aluminum is soft and sticky.

Would a few hours in the freezer before using the QMAX help?

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[Doug in Indy]

I use ordinary spade bits at a fairly slow speed, and WD-40 lubricant. I have a drill press, but I don't think it is required. It makes a clean hole, but is the bits don't last very long. You should be able to get 4-6 holes before they die. They're pretty cheap. Be sure to support the underneath side with wood, and drill a pilot hole - maybe 4-5mm.

 

[mickeymoose]

Use a Greenlee, with the boss entering the metal from the outside so the burr will be on the inside of the chassis. There will be no distortion in the aluminium. Always cover all visible areas of anodized (goes 2x for black!) aluminium with masking tape before any work to avoid scratches.
Good luck in DIYing! E

 

[JammyBStard]

I've ordered a 22.5mm Q.Max and I will certainly be following advice on taping off the area.

Thanks all

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[Nico Ras]

It is more commonly known as a chassis punch, you get all sizes and shapes even for D type connectors, etc. Google chassis punch and look at the images.

 

[jacco vermeulen]

Would a few hours in the freezer before using the QMAX help?

Working on metal/alloy in summer or winter makes a difference.
The elasticity (zone) reduces with dropping temperature, to zero at zero kelvin. -18C (255k) is 15% down from +27C (300K).

Aluminum is a bit different in a number of ways, compared to other metals.
One is the strain/stress curve, the elastic region flows over to the plastic deformation area, without a hump at the crossing.
Elastic stretch of aluminum is several times the one of steel (at an identical force level)
Between the two, the effect of temperature difference is most noticeable with aluminum. Easiest to see by grinding aluminum at different ambient temperature levels of summer and winter.

How long the freezer trick will last when drilling depends on the mass and the sharpness of the cutting tool.
You'll still need to lubricate the drill.

(The elasticity behaviour of aluminum makes it the ideal material for yacht building. There's a classic example of a sailing yacht that went down, the alloy hull stranded and rolled over rocks for weeks. Totally plastic deformed skin, zero rupture. Any other hull material would have been shredded to pieces)

 

[infinia]

The elasticity behaviour of aluminum makes it the ideal material for yacht building.

are you sure , highly debatable when you consider all the other factors.
aircraft has moved away , HP yachts will follow in the coming decades.