Hole saws in thick steel

[fizzy]

Best advice. Don't!
I needed 3x 35mm holes in 12mm steel plate. My rotobroach cutters are 38mm unfortunately. I bought a Starrert hss hole saw with 8% cobalt. Ran it slowly in the Bridgeport. About 200rpm. Used flood coolant. Started well but soon stopped cutting. No chip clearance so needs constant blowing out. After 1 hole it was knackered. Off to Screwfix and bought a Bosch hss cobalt. No arbor with pilot drill. £25 extra . I didn't bother. Held it in an ER32 collet fine. Pilot drill not necessary either.
After 1 hole it also died
@DAPPH said he could fix it. I was rather dubious but fair play 2 minutes with a triangular file and it was as good as new again!
Rotobroach always from now on!

 

[Agrismith]

Best advice. Don't!
I needed 3x 35mm holes in 12mm steel plate. My rotobroach cutters are 38mm unfortunately. I bought a Starrert hss hole saw with 8% cobalt. Ran it slowly in the Bridgeport. About 200rpm. Used flood coolant. Started well but soon stopped cutting. No chip clearance so needs constant blowing out. After 1 hole it was knackered. Off to Screwfix and bought a Bosch hss cobalt. No arbor with pilot drill. £25 extra . I didn't bother. Held it in an ER32 collet fine. Pilot drill not necessary either.
After 1 hole it also died
@DAPPH said he could fix it. I was rather dubious but fair play 2 minutes with a triangular file and it was as good as new again!
Rotobroach always from now on!

They work better in a hand drill. You can rock them side to side so only cutting a small amount at a time. 12mm might be a bit ambitious but I've done a few holes in 6mm with a cheap erbauer hole saw. Broke all the teeth after a 5 holes but that was all I needed. Probably would have lasted longer but broke the pilot on hole 2 so was wandering a bit.
Wouldn't be first choice but wasn't dragging the generator and mag drill up 2 flight of stairs and down 15min walk along a severely overgrown canal tow path

 

[brightspark]

had to put 4 x30 mm holes through some i beams in 12mm steel up through a roof support using a hand held electric drill and a hole saw and used rocol cutting compound worked perfectly and cutter still sharp at the end but you have to have muscles like popye which i did at the time

 

[Onoff]

I used these cheap eBay jobbies to cut a bunch of holes in 5mm stainless with an ancient pillar drill, Rolson or Nu-Tool it was:

https://flic.kr/p/2huprYo

Did 3 of these plates with one cutter:

https://flic.kr/p/2hmbZ3D

 

[brightspark]

plenty of paste and doing it in a pillar or hand drill drill works well as you can back it off quick for swarf clearance

 

[Kram]

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.

 

[Gragson]

about 30mm + deep, bosch progressor H/saws, aldi bandsaw, pillar drill

 

[fizzy]

I have no idea what variety of steel this plate is. Cut lovely on my big Startrite though!

 

[minimutly]

I made an inlet manifold flange for a 16 valve head, from 8mm stainless using a Starret hole saw, two holes per port. Went through 3 holesaws....
Long time ago, before I had any machine tools other than a pillar drill.

 

[fizzy]

I do love that Startrite bandsaw. Even with the length I cut the width was within a thou measured all along

 

[Onoff]

Morse brand cobalt hole saws, the red ones, are / were good

 

[MetalMonkey]

If you are cutting either the hole or slug to waste - and they don't need to be perfect, then drill a couple of swarf clearance holes to intersect the cut line, either just inside, outside or on directly on the middle.

It will greatly improve the cut speed and longevity of the saw. It is swarf clearance that is the problem with holesaws, it packs the cut up and causes the saw to overheat, and then they are done. The only other way is to peck drill and clear the cut often.

 

[not done it yet]

If you are cutting either the hole or slug to waste - and they don't need to be perfect, then drill a couple of swarf clearance holes to intersect the cut line, either just inside, outside or on directly on the middle.

It will greatly improve the cut speed and longevity of the saw. It is swarf clearance that is the problem with holesaws, it packs the cut up and causes the saw to overheat, and then they are done. The only other way is to peck drill and clear the cut often.

This^^^!

made an inlet manifold flange for a 16 valve head, from 8mm stainless using a Starret hole saw, two holes per port. Went through 3 holesaws....
Long time ago, before I had any machine tools other than a pillar drill.

A pillar drill, with stainless, was likely too fast and insufficient feed rate.

 

[KemppiFrog]

Cut a whole bunch of 50mm holes in 6mm SS. Used Starret holesaws. Strapped another motor on the back of my Meddings to halve the lowest RPM and lots of cutting fluid. Can't remember how many holes per saw, but it was a lot.
If I don't want to use a pilot, I first cut a hole in a bit of 10mm ply, then clamp that to the work as a guide.
Occasionally sharpen hole saws with a thin cutting disc..

 

[prepman]

Best advice. Don't!
I needed 3x 35mm holes in 12mm steel plate. My rotobroach cutters are 38mm unfortunately. I bought a Starrert hss hole saw with 8% cobalt. Ran it slowly in the Bridgeport. About 200rpm. Used flood coolant. Started well but soon stopped cutting. No chip clearance so needs constant blowing out. After 1 hole it was knackered. Off to Screwfix and bought a Bosch hss cobalt. No arbor with pilot drill. £25 extra . I didn't bother. Held it in an ER32 collet fine. Pilot drill not necessary either.
After 1 hole it also died
@DAPPH said he could fix it. I was rather dubious but fair play 2 minutes with a triangular file and it was as good as new again!
Rotobroach always from now on!

Not had issues with starret ~30mm on 12mm plate, but I probably(?) run them at 120rpm or less with plenty of expensive cutting oil. Used to burn them out in my younger days running them too fast (HSS?) But now I have to pay for them and not the employer.

 

[oldbikedavey]

I do love that Startrite bandsaw. Even with the length I cut the width was within a thou measured all along

The extra fence is nifty. Could set that up with a shaper gauge for added parallelism.....

 

[8ob]

had to put 4 x30 mm holes through some i beams in 12mm steel up through a roof support using a hand held electric drill and a hole saw and used rocol cutting compound worked perfectly and cutter still sharp at the end but you have to have muscles like popye which i did at the time

Thats my take on it BS, the bigger they are the more pressure needed. Like any big drill, go to lightly and you will rub off the cutting edge. @fizzy I now have BIC ( bandsaw inferiority complex)

Bob

 

[MattF]

Just bandsaw?

 

[Agroshield]

The extra fence is nifty.

I would respectfully suggest it is not such a good idea. Unless the two sides of the piece being cut are straight and parallel, it will overconstrain the piece and not help. If we look at a table saw for wood, they do not have a double fence for the same reason. An important principle in cutting is to use one and only one reference edge.

 

[Sam0117]

I find doing larger holes in steel using a HSS holesaw if you put one or two 6mm holes near the edge your cutting it helps remove the chips and of course plenty of cutting fluid, that’s if you don’t want the centre blank obviously