I never realised this stuff was so hard. I need to drill 24 x 4mm holes in a 3mm thick sheet. I have a drill press but the ordinary HSS drills give up after one pilot hole (2mm pilot hole). I managed to drill 2 of the 4mm holes before that bit became blunt. (It was blunt during the first hole but I persevered). I am using lubricant but wondered if its worth investing in a (expensive!) cobalt drill. Are these much better than HSS? Or should I just buy a cheapo pack of 10 HSS and write them off after each hole? (I know you can sharpen them but I havn't got the skills). Thanks for any advice/comments. diymostthings
Stainless steel 3mm sheet is'nt that tough to drill! Your dill bits must be c r a p. What speed have you got the drill press running at? Snezza31
Thanks Snezza31. They are standard HSS drills as supplied by Screwfix but for the price of 10, I could get one cobalt drill bit. Speed is slowest ( I think about 120 rpm) I can get. Should I get a good branded make of HSS drill then (e.g.is "Dormer" OK) or invest in a Cobalt. Is a cobalt that much better anyway? Thanks again diymostthings
Dormer are good quality drill bits. If you try these, they should drill it with no problem. 120rpm seems too slow for 3mm stainless steel! Especially with such small drill bits of 2mm to 4mm Dia. Have you tried a "NEW" drill bit? Snezza31
If you find they are blunting, try the 'press, release, press,release, press, release' method. Keeping the bit in contact for only one second. Mr. HandyAndy - Really
Thanks for all the advice - so it looks like: 1. Quality HSS bits. 2. High speed in drill press (1200 rpm). 3. Use cutting paste (rather than lubricant). 4. Use the "press/release" technique. (presumably to avoid overheating and tempering of the bit) Very grateful to one and all! Much more confident now! diymostthings
The advice I've had from engineers in the past is to use a constant pressure in SS not press/release but see what works best for you.
Don't, whatever you do, let the drillbit heat up as this work-hardens the stainless, then you really will have problems. As said further up, around 1200 rpm should be OK and plenty of cutting fluid/paste, and steady pressure so the drill bit is always biting into fresh material. Oh, and some half-decent drillbits
This post is that old, I think he'd have drilled them by now, that or given up and started a new project.
OK, point taken you pair of smart Alec's, I'll make sure to check the date of posts in threads from now on p.s. don't go accusing me of being enthusiastic
There's a bit called a uni-bit made by Irwin it is the shape of a cone and has an increasing width, I found the the best bit to use when drilling steel, there also bits available made from aircraft steel, which stay fairly sharpe, I fitting alarms in 156 house at Patrick Air Force family housing and the ground floor was all steel I was using a 12" long at 4/16 and 3/8' also be a good idea to have a drill bit sharpener around.
Just adding to for anyone else searching for help cutting stainless. The DeWalt extreme2 bits from screwfix drill stainless no problem with a cordless, start stop often and keep speed lowish. Keep the heat out and don't rush.
Don't apply to much pressure lit the bit do it's job by pushing to hard you causing the bit to blunt out faster I keep a grinder close bub and studied the origami a format of the drill bit end and replicated it.
I was the OP - I finally drilled them without a problem- in Spetember 2012! Iwas simply running the drill press too slowly. With 1200 rpm and constant pressure I didn't even need a pilot hole. I got through 31/2 drill bits though. Thanks for all the advice diymostthings
That's the problem....When it's blunt, then just chuck it & get a new one. Us old apprentice trained blokes were taught how to sharpen a drill. It don't happen now.
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