TiN coated twist drills

The other day the bulb on the security floodlight blew.

I thought ‘no problem I’ve got a spare’, so up the ladder and attempt to remove the screw which holds the front of the light on.

No luck with a screwdriver because the body of the light is aluminium while the screw is steel and the two have grown together. Even a couple of days of soaking with Plus Gas had no effect.

So the next idea was to drill out the screw. The screw was hard so the HSS drill was being blunted with very little progress being made. In the end I ground a 5mm masonry drill to be reasonably sharp and that drilled out the head of the screw. The end result was not entirely satisfactory as I couldn’t drill out the threaded part of the screw.

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

As I have, over the years, inherited several hundred HSS twist drills I have never bothered to look into TiN coated twist drills which give the impression that they would solve this problem.

I would be interested to hear other peoples experience of TiN coated drills and whether they would be able to cope with a similar job.

Thanks

Jon

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

I agree with Howard except to note as a point of detail that Titanium Nitride increases hardness as well as reducing friction.

TiN extends the working life of drills rather than giving them super powers. The layer of TiN is very thin and just underneath lies an ordinary HSS drill. Once the skin is damaged, the drill wears out as normal.

I'd be inclined to try a left-hand twist drill. These tend to undo screws as they cut giving a reasonable chance seized screws will release without having to drill them out completely.

Dave

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

always having this problem........

have now learnt to take everything to bits and lube the threads....when fitting new...

this includes ride on mowers etc........

save's loads'a time over the years ......

all small screws are changed for ST/Steel and around the exhuasts, brass fixings ...even if I have to make em.....

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

2nd that. Used to use cobalt drills for my work. Drilling lots of stainless & steel girders. Lasted around 4 times the standard H.S.S drills. Don,t forget the Copper slip on re-assembly.

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.

Mmn I have a few LED floods fitted. One at back of garage just gone duff at 18 months old. Not expensive though.

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.

+1 for cobalt drills

I bought one of these sets to drill an extra dowel hole in by Dickson toolholder block - went through it without drama. Highly recommended.

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?

A good heat sink is a must for high powered LEDs that are driven hard. Even though they are more efficient, they still produce heat - and one thing LEDs don’t like is excessive temperatures.

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 working I sometimes encountered wood screws that would not shift.I heated a thin rod and held it on the head a kept it red hot with a torch, the heat transfers to the screw and expands it.Left to cool and shrink they unscrewed.I have tried this in metal with success.

Frank

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.

I have fitted many of these lights over the years and the first thing I did with a new fitting was to replace the screw with a brass nut and bolt. Never had a problem with those fittings afterwards. The screws as fitted are A-P-I-T-A !

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

Thanks for the comments.

The Cobalt and Locksmiths drills sound interesting. I'll look into getting a small set of one or the other to insure I don't have to this sort of thing again!

Thanks again.