Making large[ish] holes in steel - occasionally - how?

[tinnews]

What do others here do when they want to make a big[gish] hole in a lump of steel?

I drill lots of holes in the 2 to 6 mm range, dead easy.

I drill some holes in the 6 to 10 mm range, fairly easy though I could do with a slower drill.

Then I'm stuck really. OK, up to 12mm 0.5" I can drill a 10mm hole and then make it bigger by various dodgy means but above that I'm a definitely stuck.

Recently it would have been very convenient to have been able to make some 20mm (or thereabouts) holes in some angle but I really couldn't think of a reasonable way to do it.

None of my drills (corded or cordless) has a chuck which goes beyond

12mm or so and anyway they're too fast. I don't think your standard 'hole saws' (those circular hacksaw things) would get very far in steel, they're what I use on wood, plasterboard, etc. when I want big holes.

So are there any reasonably cheap tools for making the occasional large hole in steel? It doesn't have to be fast, taking several minutes on one hole doesn't really matter.

[dom]

I think

sell reduced shank drills, but for larger holes in steel a drill press makes it far more do-able.

[Cicero]

================================== Blacksmith's drills:

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[Cicero]

================================== If you don't like the cost of Blacksmith's drills you can experiment with an old trick to make a small drill behave like a larger drill. You re-grind a bit so that the point of the bit is offset to one side. When you drill a hole with such a modified bit the hole produced will be larger than the diameter of the drill because it is cutting eccentrically. It does work but you need to take care with the grinding to get the correct hole size.

Cic.

[tony sayer]

In article , [e-mail] scribeth thus

A bench drill isn't that expensive these days and with some reduced shank drills you should be able to do that without much trouble.

What makes a big difference is lubricant, 3 in 1 oil is fine for steel..

[The Medway Handyman]

Decent quality holesaws like these

will cut steel easily. Start at 16mm.

Cheap holesaws, as you say, are only good for wood, plasterboard etc.

[fred]

One of these in a slow pillar drill -

your fingers away ;)

[Harry Bloomfield]

[e-mail] brought next idea :

An HSS hole saw used carefully and with cutting compound. A circle of small holes can be made which almost join up, then knock the centre out. If you are not too bothered about the finish and have a welder, you can burn your way through by turning the current well up, then finish off with a grinder.

[geoff]

In message , [e-mail] writes

if you have a sense of adventure ...

[The Medway Handyman]

Great! Much better than an angle grinder :-)

[nightjar]

Electrician's hole saws, which are intended for cutting holes in steel trucking for fitting conduit. For larger holes I use a fly cutter, but they do need care.

Colin Bignell

[nightjar]

"nightjar .uk.com>"

That should read steel trunking and this time I've disabled the spelling correction.

Colin Bignell

[John Rumm]

nightjar > Electrician's hole saws, which are intended for cutting holes in steel

To be fair, they would probably work fine on trucking as well ;-)

[cerberus]

A decent hole saw will cut steel.

If you know someone with a lathe you can have the drill shanks turned down.

Don.

[R]

Gas axe

[somebody]

In message , [e-mail] writes

[snip]

Google for a "mag drill". I think 'cheap' ones start around 250+vat ish, maybe you'll find a deal on ebay.

Saw one in action on 10mm plate, it was like a hot knife through butter.

Hth Someone

[tinnews]

I do actually have a bench drill, goes down to 500rpm or so. Maybe I should invest in some reduced shank drills for it then. In most cases I should be able to get the workpiece under the drill.

[tinnews]

They look good, thanks, probably only when I want to cut quite a few holes of one particular size though as they're moderately expensive.

Good for that though! :-)

[tinnews]

Those are definitely the 'bodgier' end of the possible ways of doing it! :-) I have used the 'ring of holes' method when desparate but it is rather time consuming and the result is usually a bit messy.

I hadn't thought of using the welder, I do have one and I guess it would be capable of burning a hole in 1/8" angle, the risk would be overdoing it.

Thanks for the ideas so far everyone.

[tinnews]

Ah, now that looks like a good way to go, not exorbitantly expensive and will probably be quite OK for the sort of number of holes I want to cut. Thank you.