Stainless steel drilling

[Wing Mark]

I have not had much success with standard bi-metal holesaws in stainless but you might be OK with a new good quality one with lots of cutting fluid. I have had better results with TCT holesaws on stainless like these.Starrett TCT

Carbide is always a good answer when working with stainless that some other sod has work hardened.
Those Starrett tools are not stupidly expensive either.

 

[wizard]

Thanks guys for all the help and advice. The pillar drill arrives early next week.
This will give me time to find the cutters suggested and some thick ply.

 

[BabaYaga]

As others have said, a new holesaw will easily cut through a few mm of stainless steel plate.

Coincidentally, I have just today put myself to the task of cutting a 25mm diameter hole in a piece of stainless, 10mm thick. And I don't even have a proper pillar drill, just a handheld on a stand.
It all went well, somewhat to my own surprise.
My conclusions are, for this type of work, that the crucial thing may not be to use exactly the right cutting tool. More important, I think, is to have a drill that is able to produce a lot of torque at slow speed.
High pressure was mentioned upthread. I found, at 25mm only fairly moderate drilling pressure was required (there is still a lot of friction to overcome, therefore the need for torque).
Another tip is to drill the pilot hole separately, without the hole saw attached.
Bicycle chain oil worked fine.
As for hole saw, I used this type. (the teeth are still sharp):
DeWalt DT8116L-QZ 16mm 2x Long Life BiM Holesaw

 

[Martin_J]

Well done with not having a pillar drill to hand.. I've taken stuff to the pillar drill when drilling in aluminium but stainless, as you confirm isn't too bad with the right pressure, the right tool and some cooling fluid (of any sort.. even water from the hose pipe has worked for me).

With the mention of hole saws and using them without the pilot drill, I know it might not help in this particular case but I'd never come across one of these until just now.. A hole saw guide with suction fit, a coolant guide hole and bearings that guide the hole saw itself!



https://www.amazon.com/DRILAX-Fixture-Vacuum-Suction-Coolant

Might come in useful even if just for the idea... Darn I just threw away some old bearings

 

[DownWest]

Since the OP is drilling relatively small holes at 20mm the low speed on the pillar drill will be about right. The 50mm ones required a lower speed than my drill would do. Each hole drill managed about a dozen holes in 6mm 304

Edit, that looks fun, if one has a lot to do.

 

[jamie N]

As a thought, has anyone ever done this sort of thing with the metal immersed in a 'bowl' of some sort, to keep the drill cool. I realise the possible implications of electricity and water (I'm an ROV pilot), but reckon it'd be quite easily feasible.

 

[DownWest]

As a thought, has anyone ever done this sort of thing with the metal immersed in a 'bowl' of some sort, to keep the drill cool. I realise the possible implications of electricity and water (I'm an ROV pilot), but reckon it'd be quite easily feasible.

Big drift... But a friend cut the mirror for his reflecting telescope out a thick chunk of glass. Cut a ply disc, put an ally big tube on it and mounted it in a decent pillar drill (Army, so big w/shop with proper kit)
Made a dam with putty and filled it with water and griding compound. The ally picked up the compound and he set it to gently come down with a light pressure. About an hour or so later, he had a glass disc about 1 1/2" thick.
As a result of the a fellow officer in the mess doubting it could be done and a bet, the doubter had to wear the bit with the hole around his neck for the rest of the evening.