Cutting a large round hole

[petro1headParticipant @petro1head]

I need to cut a hole in some 2mm alloy sheets. Its for a computer as I want to add an extra 120mm fan.

I was just going to but a hole saw from screwfix **LINK**

Any advice ie should I sandwich between 2 pieces of wood

[petro1headParticipant @petro1head]

[JasonBModerator @jasonb]

Have you got a boring head, could do it with that.

[Neil WyattModerator @neilwyatt]

Posted by petro1head on 21/11/2018 18:29:53:

should I sandwich between 2 pieces of wood

I would, then it should be easy.

Make sure it is well clamped, if it can move, it will.

Neil

[petro1headParticipant @petro1head]

I have Jason but it not big enough

Cheers Neil

[Anonymous]

Mark the centre, scribe the circle with dividers, drill, saw, chisel the centre away, file to the scribed line. Shouldn't take more than 10 minutes or so in aluminium.

Andrew

Edited By Andrew Johnston on 21/11/2018 19:08:23

[petro1headParticipant @petro1head]

Jason, I think the hole saw option will be quicker and neater

[Carl Wilson 4Participant @carlwilson4]

The hole saw option will be a complete dogs breakfast. Hole saws tend not to be especially round and you will end up with an oversize/oval hole.

The way to do this is to use an abrafile in a fret or coping saw. Mark it out with dividers then drill a small hole to get the abrafile in. Then saw out your hole.

Minimum amount of filing then required to achieve the final dimension.

Abrafiles are now sold labeled up as ‘rod saw blades’ I believe.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Carl Wilson 4 on 21/11/2018 19:41:33:

Abrafiles are now sold labeled up as 'rod saw blades' I believe.

.

Do you have a link to a reputable supplier, please, Carl ?

I have yet to find a decent modern equivalent to the original Abrafile.

MichaelG.

[Ian HewsonParticipant @ianhewson99641]

The hole saw will cut a decent hole if used in a drill press and the plate clamped to a wood backing piece, I have done thousands over the years, usually freehand in a pistol drill.

The saw you link to will need an arbore to mount it though, a cost effective method would be the drill and file method.

Not a long job in aluminium.

[alan ord 2Participant @alanord2]

When I was making the splashers for my Pansy loco I made steel mig welded "cans / tubes" from 1.6mm thick steel sheet. The diameter from memory was around 5". I used a cheap treppaning tool in the drill press, clamped onto a sacrificial piece of wood on the table. Cutting half way through and turnoing over to complete the cut. Filed away the burs before going on to weld it to the rolled centre piece worked out well.

Should be a dodle with aluminium.

Alan.

[martin perman 1Participant @martinperman1]

I smear tap/die lubrication which helps the hole saw work.

Martin P

[Carl Wilson 4Participant @carlwilson4]

I’ve also yet to find an equal to the original abrafile. I have a small stock of originals that I use carefully.

I think the nearest equivalent now is a tungsten carbide tile cutting saw blade. Not as good as an original abrafile but should do a good job on the above.

A 120 mm hole saw is going to make a right mess.

[JasonBModerator @jasonb]

You don't need a big head, just a tool out the side, this quick video was done for Ron in his boring head thread but I just used scraps of 2.5mm ali as an example.

 

Not a bad finish

 

 

Edited By JasonB on 21/11/2018 20:31:52

Edited By JasonB on 21/11/2018 20:46:06

[John RuddParticipant @johnrudd16576]

How about a tank cutter, treppaning tool?

[JasonBModerator @jasonb]

If you don't know what a treppaning tool looks like it's the one bottom left. That would do the job too.

[EmgeeParticipant @emgee]

The tool Jason refers to as a trepanning tool is probably what John and I call a tank cutter, originally used in an old fashioned brace, or very low speed power drill.

Emgee

[vintage engineerParticipant @vintageengineer]

You need a longer tool.

Posted by petro1head on 21/11/2018 18:49:42:

I have Jason but it not big enough

Cheers Neil

[petro1headParticipant @petro1head]

Just had a look at the photos in the boring thread and now see what you mean. Will check my boring tool to see it the bit will fit the way. At the mo the tool bit points down

Edit:  yes it has  the tool it is triangular like this https://www.chronos.ltd.uk/acatalog/info%5fXP162%2ehtml

 

Edited By petro1head on 21/11/2018 23:07:30

[Marcus BowmanParticipant @marcusbowman28936]

Bosch make hole saws with fine pitch teeth, specially for cutting holes in thin sheet metal. Not cheap, though.

Marcus

[Mike PooleParticipant @mikepoole82104]

The tank cutter type tool works well until you break through, i find attacking from both sides is helpful but you will probably still need to tidy up with a file. Hole saws seem to make a hole but holding to a size is not their strong point. If you don’t mind a bit of filing then jig saw most of the waste and file to size.

Mike

[J BENNETT 1Participant @jbennett1]

As an alternative you could drill a pattern of holes, say 1/2 inch. Air flow is still quite good. If you look at a lot of computer cases you will see they rarely use one large hole, usually a lot of smaller ones, often only 1/4 inch or less.

[petro1headParticipant @petro1head]

They do that for safety reason and it does inpeed airflow

[duncan webster 1Participant @duncanwebster1]

It doesn't need to be perfect. I certainly wouldn't buy a big hole saw just for this. I think you could do it with an electric jigsaw with a reasonably fine blade, not too fine or it will clog. For ally spray the work with WD40. Support by sitting the sheet on a partly open workmate so that the blade is going between the flat bits.

[petro1headParticipant @petro1head]

Well I bought a big hole saw, will come in handy for other jobs

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