Your drills need to be sharp, and correctly ground (i e Both lips the same length – if the drill is to cut to size )

My understanding is that TiN coating cuts friction rather than hardening the drill.

Would be surprised if the screw were 12.9; more likely to be 8.8 grade at worst. These can be drilled with a sharp HSS drill.

If the screws are that hard, you would be looking for a Carbide drill, run at high speed with plenty of pressure.

With a HSS drill, letting it rub will generate heat which results in the steel loosing its hardness and blunting rapidly.

Try a sharp drill ,and don't let it rub. Keep the pressure on so that does not rub.

HTH

Howard

Good advice!

DD NOT use an Easyout. The most misnamed tool in the workshop.

More likely to expand the screw before it breaks, so you never get it out!

You could try giving a few bangs on the end with a mallet, in the hope of breaking the corrosion between the screw and the housing. Possibly followed by some more WD40. When the screw is out, the replacement should be greased to prevent any future recurrence.

Howard

Jon Berk said" "I have done this type of thing before but would like to have a ‘less crude’ way of drilling hard steel."

I'm quite fond of "cobalt" drill bits as a way of getting through hard materials faster than standard HSS bits. They are a little more prone to breakage than plain HSS bits but not as brittle (or expensive) as carbide.

I'd try a LH drill bit first (not necessarily cobalt), as Dave suggests, then if this fails tentatively try a high quality screw extractor (poor quality ones will do more harm than good). Lastly, if this too fails, drill out with cobalt, and if necessary retap the hole.

Edited By Bill Phinn on 03/01/2020 17:33:43

Had similar problems with garage security light a couple years ago; it was a Halogen bulb type, which I never limed in the first place, any way like others, once I removed the screw it was replaced with an SS screw coated with 'Copperslip'. I have since replaced the Halogen light when it blew again last year with a LED unit from Aldi, no more blown bulbs ( LED's ) I hope. Usual disclaimer applies.

George.

The same has happened to me, but I replaced the "non-replaceable" 10 W LED chip (cost about 50p) and it worked like a new one. Still going strong a couple of years later.

This is interesting as I want to put up a security light and was wondering about replacement “lamps”. Do you have a link for the chip?

Your first mistake was to TRY to drill out the screw ! Ali has a high expansion rate( though will melt at about 700c) so heat is the best trick, several cycles of heat/cool, and gentle impact on the head, this gripped in a mole wrench or similar. Patience is a virtue ! Stainless replacement fastener will help, but won't stop the ali corroding.

The reground (on a green wheel) masonry drill bit is a much underrated tool. properly sharpened it will drill most things, but high speed and pressure are important ! For stainless the hss drill MUST be very sharp and if it rubs once your in BIG trouble, now it's time for carbide tips.

As for LEDs, forget 10,000hrs, faulty solder joints, or chips, and poor quality drivers will drasticly reduce that.

Just like soft start grinders, where the switch is electronic and won't last long . WHY do I need soft start ?

If I can't handle the starting torque reaction I should NOT be using the tool at all.

YES ! Yes, I know, health and safety !!!! Noel.

When I had a similar problem, cut through the screw and used a piece of wire wrapped around to hold it together. Cheap, quick and works.

Jon,

One other option (along the lines of your reground masonry drill) would be "locksmiths drills" which are normally ground drills, but with a carbide tip.

Got mine off ebay for £2-4 a piece and have been handy when drilling harder materials (or drilling out broken screws, etc.).

Regards Tom