Advice wanted in drilling holes in hardened metal

[gouldsborough7]

Guys
Getting my two-pennyworth at the moment with messages. I am in trouble with trying to drill through what I think is hardened metal.

The interior mirror that was fitted to my newly-bought Hunter was a naff plastic thing, that vibrated all over the place. Rather than buy another stick-on mirror, I went for a classic style of screw-on type. All that was needed was to drill 2 holes in the windscreen surround, pop in some self-tappers, and Bob's your uncle.

Like a lot of 5 minute jobs, I spent about half an hour getting nowhere. Tried several drill-bits (freshly sharpened), also a smear of oil (sometimes works), but all I succeeded in doing was putting a tiny dimple in the window surround.

Questions:
1) Is the window surround hardened metal? (mine is the shiny chrome-finish type).
2) Am I trying to do the impossible with amateur equipment?
3) Is there a way forward, or do I bite the bullet and go for a stick-on mirror?

Cheers
Mike

[CosworthCabrioLee]

Re: Advice wanted in drilling holes in hardened metal

Hi Mike, pleased you have got a new car, not to teach you how to suck eggs but are you using the correct HSS drill and is it sharpened in the right way ?
Any chance of some photos of the car ???

[danny_nelson]

Re: Advice wanted in drilling holes in hardened metal

The screen surround is stainless steel.

[greyV8pete]

Re: Advice wanted in drilling holes in hardened metal

As Danny says the surround is Stainless Steel. This metal work hardens as soon as you put a drill near it. Usual mistake is to use a high speed (r.p.m). Whet you need is a very high feed (ie push hard) and a very slow speed and a very sharp cutting tool (drill bit) when drilling this stuff. Also some cutting fluid designed for the job. Oil is a lubricant so will tend to make the drill skate over the metal. Paraffin would be a better choice if nothing else available. The bad news is you already have a work hardened "hole" where you started drilling. Use a Dremel or similar with a fine grinding point to cut through that hardened layer, otherwise you will just wear out drill bits. Final thought though. The screen frame is designed as a roll over bar. Any holes drilled in it, however small, will be a potential source of weakness. Peter.

[dave_kitson]

Re: Advice wanted in drilling holes in hardened metal

Hi Mike
Just a couple of points to consider. The reason for using a stick on mirror, is for safety, so that in an accident when you bang your head on it, it breaks away - a screwed on mirror would not pass IVA. Secondly, you will need a long stalk on the mirror to see out of it with the hood up - I've recently moved my stick on mirror lower down the screen for this reason (hood down no problem).
Cheers - Dave

[cabrioman]

Re: Advice wanted in drilling holes in hardened metal

I wouldn't worry too much about the hardening from your attempts so far, the answer is to use a drill bit that is designed to handle stainless. You need to go for drill bits with cobalt heads, machine mart do a full set from 2mm up to 10mm for about £22. I have used these extensivly for stainless with no problems, you only really need lubricsnt if you are trying to countersink or use very large drill sizes.

John

[gouldsborough7]

Re: Advice wanted in drilling holes in hardened metal

Thanks Guys
I did try various drill-bits in my collection, all sharpened and HHS. Even contemplated buying a cobalt set from Screwfix, John.

In the end, Stafford Vehicle Components (who sold me the screw-on type) were happy to do an exchange for a stick-on mirror. So, it should arrive in the post today with any luck. Why I didn't go down the stick-on route in the first place is anybody's guess!

Cheers
Mike