80mm hole to 90mm in 1/4" steel

[fitterski]

What's a relatively good/easy way to increase 80mm holes in 1/4" steel to 90mm? I have 4 of them to do, gas torch is out as it's too rough. Ideally I'd imagine a kind of tapered huge coarse rotary file running on air for good torque, one that self-centers and goes up to 90+ mm. It's for flange bearings with the round support ribs that seat into a positioning hole. TIA

 

[dusty3030]

90mm (3.5") holesaw in a drill or drill press if your material will fit under?

 

[fitterski]

90mm (3.5") holesaw in a drill or drill press if your material will fit under?

I can't get it to a drill press and I'd need to tack a plate for a centering hole, it's an option maybe with carbide teeth? Never used one of those before.

 

[rScotty]

What's a relatively good/easy way to increase 80mm holes in 1/4" steel to 90mm? I have 4 of them to do, gas torch is out as it's too rough. Ideally I'd imagine a kind of tapered huge coarse rotary file running on air for good torque, one that self-centers and goes up to 90+ mm. It's for flange bearings with the round support ribs that seat into a positioning hole. TIA

I don't know of any way to use a drill press as you describe. It would need keeping the cutting tool centered in the existing hole without binding - and I don't know of a tool that will do that. However, there are hole drills available in 80 and 90 mm for not too much money if you have access to a drill press that has a heavy table and ability to clamp the part down. Be sure to set the speed to dead slow, lots of down pressure, and lots of lube.

Depending on the shape of the flange bearings you are making, enlarging the hole while keeping it centered is a routine job on either a lathe or on a milling machine...In this application a milling machine is simply working like a sturdy & well supported drill press. If there is any advantage to the finished part being half way accurate that's what I would do.

I'm guessing that doing 4 of them would be roughly a lunch hour's worth of work.
good luck, rScotty

 

[wheelbuilder]

I can't get it to a drill press and I'd need to tack a plate for a centering hole, it's an option maybe with carbide teeth? Never used one of those before.

Somewhere I've seen an arbor that would hold 2 saws, using the smaller one for the guide. I think it was at Lee valley tools...

 

[chim]

I've had situations that wouldn't allow using a pilot bit in the hole saw. Maybe this would work for you. Take a scrap piece of 1/2" plywood and saw a hole into it. Then clamp the plywood onto the metal and use it to guide the hole saw. On smaller holes I've used a cordless drill with a small stream of water to flush chips and keep it cool. With a hole saw that big, a heavy duty 1/2" corded drill (on a GFCI if flushing with water) would probably be needed.

 

[radioman]

what i had to do couple times in wood when i need to go one size bigger with my holed saw is put the bigger saw on first then the old size inside. I would drill until i was half way through then remove the smaller hole saw with pliers. usually the smaller hole saw just sticks out enough for pliers and havent had any problems . the only advice i can give you is before sure you remove the smaller hole saw before cutting thru so the remnants doesnt get stuck between the two hole saws making it hard to remove. i am pretty sure this will work on metal as long you stop 1/8th way in and it should be enough to hold the larger hole saw in . good luck

 

[Zebrafive]

Is there a way to bolt or clamp metal behind the hole? If so, it could be drilled pilot size first (1/4") for a hole saw.

 

[M5farms]

drill pilot hole and a few packs of metal jig saw blades and a gallon of oil ,.

 

[Birdhunter1]

I've had situations that wouldn't allow using a pilot bit in the hole saw. Maybe this would work for you. Take a scrap piece of 1/2" plywood and saw a hole into it. Then clamp the plywood onto the metal and use it to guide the hole saw. On smaller holes I've used a cordless drill with a small stream of water to flush chips and keep it cool. With a hole saw that big, a heavy duty 1/2" corded drill (on a GFCI if flushing with water) would probably be needed.

I have done this exact thing and I have tacked a strap across the existing hole with a pilot and drilled away. You can use a good cordless drill, its just 1/4" steel and will work for a few holes, drill for a bit, let it cool, drill some more. If you have 20 to do that would be a different story.