Drilling Stainless Steel

During the installation of a Solar PV system on the house roof, I had to drill many 12mm holes( 350 holes..) in 6mm Stainless steel sections ( 316 grade).

A Cobalt drill did approx 50 holes at which point the exit burr extended 2 to 3mm.

I used 3 Cobalt drills ( conventional conical point) for approx 150 holes and ran out of drills in the town...

The only drill I could find then was a RUWAG bit - RUWAG always struck me as a Weekend DIY store supplier, and I had no faith in the product 'quality' - based on no experience whatsoever. Anyway, purchased 4 of these drill bits:

https://ruwag.co.za/products/turbo-metal-drill-bit?variant=12690802606174

Even that name put me off!

The result after 74 holes, with the SAME drill bit!!

Coolant was used, - a squirt bottle with soluble oil/water mix, one liberal squirt at the start of drilling ( the conical bit required a second squirt halfway thru the hole..)

Slight crumbling of the corner edges

Nice cuttings..

Part drilled hole

74th Hole entry (top) and exit (bottom) burr

Who would have thought!

Edited By Joseph Noci 1 on 25/02/2023 06:51:21

That is very impressive performance, Joe … and I note the extensive range of sizes

They must know a thing or two about materials, and about grinding !

MichaelG.

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Edit: __ I’ve just found the U.K. site

https://ruwag.co.uk/collections/metal-hss-drill-bits

… but it appears we only get 25x performance, not 50x 

Edited By Michael Gilligan on 25/02/2023 07:22:40

Thanks for that, it's very good information. I've no thoughts of tackling such a job.

Photos are brilliant.

Good afternoon all.

I don't envy you that job!

Sometimes an unknown or 'car boot' sounding drill can be a pleasant surprise. Years ago I bought a set of drills that was on offer called Turbomax. The tips were similar to the Ruwag drill you used. They were pretty good, & when blunt I re ground them to normal points. They lasted several years.

A316 does give drills a hard time, and keeping them cool is the trick. I did a job once that involved drilling 60 8mm holes in some A316 square bar for some kind of gate mechanism. On the mill using auto feed and suds everywhere I very nearly got all of the holes done with a single HSS drill.

Cheers.

Stewart.

A/k/a "pilot point" drills. Black & Dekker used to sell them and I got a set later with the Elu brand. They are very good, kind of a cross between twist drill and slot mill. Excellent for drilling starter holes in the lathe where rather than start with a pilot drill that can wander you use a drill close to the finished size that drills its own pilot and is much more rigid. Also in my experience drill much truer to size. Great link Joe & Michael, now I have another source.

Dewalt, who are Black and Decker, still sell them. They're described as a cobalt drill, unlike this particular Ruwag offering.

Very nice drills, shame that quality is not cheap, though. I find that high pressure and slow speed works best with stainless steel.

.

I only bought one 2mm and two 3mm versions from the U.K. site

… mainly to see how well they were ground, at that size

Give that postage is free if you spend at least £5 the price seemed reasonable enough.

MichaelG.

Well …The drills arrived safely today

My main reason for purchasing them was to see how well the ‘2-stage’ shape would be ground at small diameters [see Joe’s photos for the advertised shape]

First inspection was a little disappointing:

This is the tip of 3mm drill from the same series:

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.

The tip looks ‘slightly thinned’ but is not recognisable as the advertised shape

MichaelG.

That drill is not correctly ground for any useful purpose.

Tony

That's a shame, Michael. It's not at all what was advertised. It's a standard profile drill, from the look of it, but with a very thick web.

Oh dear

i just ordered a 25 piece set of the turbo drills today after all the rave reviews

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Probably true, Frances … investigating that was my primary motivation

But the fact remains that they come in packets displaying that ‘pilot point’ as a feature

MichaelG.

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Edited By Michael Gilligan on 28/02/2023 19:03:12

Yes, that sharpening pattern/profile seems to be known as "Pilot point" these days.

Previously I'd known it as "Bullet Point", a term which now seems to normally reference a particular profile of carbide insert masonry drills.
https://www.amazon.co.uk/Black-Decker-Precision-Masonry-Germany/dp/B07JN4SVTM/ref=asc_df_B07JN4SVTM

I thought I was imagining/mis-remembering things, but I've just been out to the workshop and found one very shiny metal drilling bit stamped up as "8.2mm Bullet HSS West Germany"; I've had it for many years.

I've also just spotted an advert from a firm I'd never heard of, selling this profile at a much lower price, though I've no idea what quality they might be.
https://www.in-excess.com/products/bbw-germany-hss-tin-pilot-point-metal-drill-bit-11mm

Edit; Just found these on eBay advertised as BBW but stamped Bullet as per my old one in the workshop
https://www.ebay.co.uk/itm/223869029049

Bill

Edited By peak4 on 28/02/2023 19:33:07

I have just submitted the following, as a review on the RUWAG web-site:

[quote]

I have not yet tried the drills [which arrived promptly and safely, thank you] but my initial reaction was disappointment … The 2mm and 3mm drills do not feature the ‘2 Stage Drilling’ grind which is advertised.
I realise that this would be difficult to execute, but that is exactly why I ordered them … I wanted to see how well it was done !
.
My comments, with photographs, can be seen on the Model Engineer forum, at
https://www.model-engineer.co.uk/forums/postings.asp?th=185942&p=1
If the drills prove to be as capable as they are described, then I will happily update that thread.

MichaelG.

[/quote]

Does it take time to see your review Michael or has it been removed?

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I have no idea, Ian … it’s the first review i have ever submitted to RUWAG

and I posted the comment here immediately after I submitted it.

MichaelG.

I have some B & D " bullet drills to &,yes, do seem to drill tighter tolerance to size than conventional.

I believe they were( & maybe still are?) made by 'Bayricshe Boherwerke' in Germany.

The later DeWalt cobalt ones feature a faster spiral i believe.

This may be advantageous to the original OP task of drilling stainless but as i'm still stuck in the 1890's i regard fast spirals with all due suspicion that 'Old Nick' had a hand in them. Certainly they (fast ones) do not mix well with Brass.

@ Michael Gilligan ~ i think you'll find the pilot point starts @ 4mm dia on these series of drills.

@ OP~ my hat off to you sir, not sure i'd fancy drilling 12mm holes in stainless with a hand drill even if the drill bits were made of kryptonite.

I'm given to understand slow speed , high speed is the required recipie for sucess drilling stainless.

Assuming your review was less than 5 stars, Michael, I'd say the current showing of only 5 star reviews for every single kind of drill bit on that site does not augur well for your own review getting an airing there.

Worse, the wording used in a worrying number of those reviews smacks of fakery to me.