Cutting neat holes in sheet metal

[Brad93]

They do make square hole punches too - rs carried a good selection.

I use the starrett/armeg/dart style short holesaws - the one piece ones not the interchangeable arbor ones.

I keep a few of the round knock out/punch ones on the van for when i can't get a drill in or there's cables on the other side. Drill a small 6mm or 8mm pilot and away you go.

 

[Dr.Al]

Urmm, I'm not sure. I think I've tried holding it vertically, pressing the button (to punch through the sheet) and then following round the template. I've also tried moving it and (while moving) pressing the button. I've tried with the tip touching the sheet and with it lifted about 1 mm off the sheet (through use of a thicker template). I don't think I've tried angling it though, nor have I tried drilling a start hole.

I'll go and have more of a play, thanks.

 

[Erie Fred]

Draw it on CAD, send it out.

 

[Agroshield]

I don't mind the idea of a bit of filing to tidy up an edge...

Maybe scribe a 23mm and 24mm dia. circle next time you use your current 22mm holesaw and see how far off it is.

Then perhaps a 20mm or 21mm one would need minimal file clean up.

 

[Kram]

Aluminium is far more pleasant than steel for hand work and quite rewarding when you get a nice edge. Decent files make a big difference.

With plasma, full power and move fast whilst watching that it cuts through and sparks below. I generally leave 10mm extra for cleaning up but I have had little practise.

For the rectangular ones, drill a central hole and use a carbide endmill in a trim router. Use this style of jig to constrain the size:

That idea scares me. Endmills are likely to bite too much, snap, kickback or jump at you.
A die grinder and carbide burr make quick work of steel and are very controllable, ideal for the task. When using freehand you just have to keep it moving.

This is what I use, takes Makita or clone batteries.

https://www.amazon.co.uk/gp/aw/d/B0D964D57S

 

[Agroshield]

A die grinder and carbide burr make quick work of steel and are very controllable, ideal for the task.

Thanks. A die grinder burr in a trim router might be the best of both worlds. You have the more controllable cutting action of the burr but the router keeps it perpendicular to the surface and the base with surrounding template means it is impossible to overcut the hole.

 

[Kram]

You can put a guide bearing on a burr shank just the same as a router bit, and clamp a guide bar to the work. I wouldnt want to use a router for it.

The other day I needed to recess a timber wall plate for a 17mm nut, I used the same die grinder and burr as for metal. Much easier than getting router out!

 

[Ian X]

Thanks both, those Q-Max things definitely look like they'll be a good option for the 22 mm round holes, but I still need to cut the other non-round holes, e.g. for these:

View attachment 476448

I have seen screw press hole cutters for DIN size rectangular control parts and indicators. No, I don't have a link but they exist. For the round holes Q-Max make a good presentable job and do not distort the plate.

 

[ajlelectronics]

Do a 2mm 3D printed template. Mark your steel and then drill around the inside edges of the intended cutouts with 3-4mm bit. Join the holes and file to shape. If you aren't happy with the result, use the template as a pretty overlay.

 

[Kram]

Drilling the corners is a good idea and I often do that but 3d printing seems a waste, just mark it out by hand .. much quicker unless you have many of the same item to make. Particually as designs often change, when you notice a part may not fit, or be fully functional in the original locations.

 

[ajlelectronics]

Drilling the corners is a good idea and I often do that but 3d printing seems a waste, just mark it out by hand .. much quicker unless you have many of the same item to make. Particually as designs often change, when you notice a part may not fit, or be fully functional in the original locations.

A thin template is quite quick to produce and the main point is that it is accurate. Marking out from scratch is more time consuming.

"when you notice a part may not fit, or be fully functional in the original locations."

That's easy to test in the template.

 

[TEO]

You can put a guide bearing on a burr shank just the same as a router bit, and clamp a guide bar to the work. I wouldnt want to use a router for it.

The other day I needed to recess a timber wall plate for a 17mm nut, I used the same die grinder and burr as for metal. Much easier than getting router out!

Why not a spade bit for the recessed nut? Slightly undersized & tapped home if you need it to grip or oversized for a socket.

 

[Morrisman]

Q-Max cutters or similar brands.

View attachment 476447

I have a set of those, ex-military. )Which means my dad stole them from the RAF when he was working there). Very useful tools, mine are mainly round but some rectangular too.

 

[Dr.Al]

With plasma, full power and move fast whilst watching that it cuts through and sparks below. I generally leave 10mm extra for cleaning up but I have had little practise.

Wow, that definitely made a difference, thanks. I'd been running the plasma cutter at relatively low current (I started at 20 A but also tried much lower).

I just went out for another quick go (with a 3D-printed template that holds the tip about 1 mm from the sheet) and turned it all the way up:

Not perfect, but miles better than I had been achieving (and the template survived largely unscathed):

That now feels to be somewhere in the territory of having the push button (or whatever) lip hide the evidence.

I'll try printing some templates for different sizes/shapes and see how I get on with those.

 

[Kram]

Thats good, I think I will need to make some templates (likely out of alu).

I believe you should have the tip touching the work. If its above, you can get sparks going back into the tip and melting/blocking it.

 

[Dr.Al]

Thats good, I think I will need to make some templates (likely out of alu).

I believe you should have the tip touching the work. If its above, you can get sparks going back into the tip and melting/blocking it.

It'll be easy enough to try with/without. I'll print some 2 mm thick templates and some 3 mm thick ones and compare the results. That sort of thing feels achievable when I'm only playing with one variable!

 

[Hitch]

Q-Max cutters or similar brands.

View attachment 476447

These, great for making panels up.

 

[Dr.Al]

These, great for making panels up.

I've ordered a 22 mm one to suit my push buttons, but there's no way I'm buying a 45mm square one, a 92mm square one, a 22.3mm × 28.2mm rectangular one, a 6.8 mm × 19.2 mm rectangular one and, and, and, and, and....

Even if all those sizes were easily available and relatively cheap, I'd be using each of them once and probably never needing them again.

 

[Kram]

I assume your template holes are bigger than the intended holes, by the dia of the torch?
How much to allow for the cutting width?

 

[Dr.Al]

I assume your template holes are bigger than the intended holes, by the dia of the torch?
How much to allow for the cutting width?

At the moment, I've just added 3 mm all round. That was based on a crude rule measurement from the outside of the torch tip to the outside of the hole in the torch tip.

I wasn't too worried about precision at this point, just repeatability. If I can consistently cut holes with a given template, I can measure the resulting holes and work out what the offset should be and then make a new template to suit.

I'm really, really pleased that the 3D-printed templates are surviving. I expected them to end up a molten mess stuck to the steel. Being able to 3D-print the templates will make it very easy to tweak dimensions and also to lay out holes relative to each other.