Cutting a 120mm hole in a case - advice please?

[stockhausen]

Can anyone suggest a reliable way of cutting holes for a 120mm fan (? 117mm hole ?) and a 140mm fan (? 127mm hole ?) in a mild steel case please?

I have looked at hole-saws and they are outrageously expensive and just about as easy to find as hen's teeth. I am not confident that I can make a decent enough job with a Dremel.

Thanks

 

[wildman]

tank cutter

but they are not cheap either. If you are not confident in your dremel skills then I suggest giving it to a proper machinist so you don't screw it up

 

[hawker1986]

I just got a holesaw when I was doing this (your right on for the dimensions), cant remember how much it was, but didnt seem too bad or I just wouldnt have bothered, where have you looked?

Hawker

 

[stockhausen]

An adjustable tank cutter seems an incredibly crude solution but it is one I have considered and may nd up using - at very slow speed and with a wooden former above and guide below - held in place by means of bolts through the four four corner holes.

Have been googling for "hole saws" & "tank cutters".

 

[bugeyewrx]

I don't think you'll get a neat hole using an adjustable hole cutter . Even with a decent hole saw it's tricky without a pillar drill .

Any metal work places near by ... don't think they would charge much .

Or see if you can find a bezel that covers the the hole edges ?

 

[JonJ678]

What tools do you have available, and how far in from the edge will the holes be?

Personal preference would be to score a circle in the paint, drill a large number of small holes near the perimeter, then take a file to it. Boring as hell but reliable, and can be done easily enough with a drill, centrepunch and G clamp.

I'm not sure a very slow cutting speed would be the way to go with a tank cutter, my hunch would be to go for a high speed but slow feed. I wouldn't even consider it with a hand drill.

I don't think you can punch a hole that large (cheaply anyway).

edit: At least one place thinks high rpm (over 40ish) will destroy the tank cutter, so it seems my guess was wrong. It recommends them for light sheet work, how thick is your case? Cutting steel is much less fun than cutting aluminium at the best of times.