Hole saws in thick steel

[Ivortheengine]

I've just done some 51 mm holes in a railway signalpost, so that's tube approx 160mm diameter with a 10mm wall. As others have said, swarf clearance is the issue. I found that cutting paste or thick cutting agents like Rocol RTD makes the situation worse, but a thin cutting fluid like Morris's Cora B really helps.

 

[RichardM]

When your holesaw is knackered, just grind the remaining teeth off and put an edge on it, makes a good hole punch for gaskets and rubber.

 

[Pete.]

The work holesaw job I ever had to do was push a 150mm hole through the 32mm web of an RSJ, working just above head height but off an ally tower probably 3m tall. We (two of us) drilled two of them in 8 hrs using a gut buster drill, taking turns in short stints with many long breaks and resulting in very tired, aching shoulders.

 

[Dcal]

Not cheap, but these HMT Versadrive hole saw are great. They have a smaller tooth than a standard slugger bit so are easier to drive.

VersaDrive® TCT HoleCutters - 55mm Deep (101030)

VersaDrive® TCT HoleCutters are highly versatile carbide tipped holesaws designed for drilling and cutting metal in a range of power tools. 12-80mm Diameter available in stock. Shop now.

holemaker-technology.com

I was using a 50mm one last night to shape a bit of scaffold tube for welding.

I ground most of the galv off and they are sitting in acid to remove the rest, because I want to tig weld them.

 

[DAPPH]

You have to oil and peck drill 1mm or 2mm deep at a time and then they last ages. I have used successfully in lathe to bore out a 42mm hole in 50mm thick steel, 25mm from each side. I also did it with a 70mm long cast iron blank, 35mm from each side.

Now then I tried a 14mm holesaw in 10mm plate to remove a snapped bit. No good, just too many teeth! I bought some spares but decided to regrind it to two teeth, that worked perfectly.

Cutting speed is also super important with hole saws , I seem ( Aging mind open to corrections here ) to recall 638 feet per minute for drills in mild steel up to 1/4 inch but for hole cutters divide the figure by half the number of teeth to get a slower cutting speed

 

[DAPPH]

Well I thought my 24" Startrite was huge - until I acquired this one
Not used it on metal yet - has a very coarse ripper blade for wood. Variable speed on the fly like a Bridgeport and a table rack feed. 36" throat!

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Psst... its cut the occasional 60 mm pallet nail in half down its length Fizzy ..guess how I know?

 

[DAPPH]

Not cheap, but these HMT Versadrive hole saw are great. They have a smaller tooth than a standard slugger bit so are easier to drive.

VersaDrive® TCT HoleCutters - 55mm Deep (101030)

VersaDrive® TCT HoleCutters are highly versatile carbide tipped holesaws designed for drilling and cutting metal in a range of power tools. 12-80mm Diameter available in stock. Shop now.

holemaker-technology.com

I was using a 50mm one last night to shape a bit of scaffold tube for welding.

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I ground most of the galv off and they are sitting in acid to remove the rest, because I want to tig weld them.

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That style cutter reminds me of the old fashioned spanner & Allen key operated boiler plate /tank cutter , the cutter follows a pilot hole for a high tensile steel center bottom plate that screws into the bottom keeper plate . A bit like a Q max cutter but with teeth at the cutter end
I've used them to pop 3 inch holes in boiler plate with ease and time . IMO they are worth their weight in gold if you can get a decent set .

 

[brightspark]

cutting the bosses for the filler caps on the blast pots with a 75mm hole saw cutter in the lathe