How to drill hardened steel

It depends just how hard the steel is but carbide drills are the best bet. The main problem with carbide drills is that they are quite brittle and need to be used with care.

Doug

You can use a masonry drill bit (with a carbide tip) at a push, sharpen the cutting angle and use coolant

Dave

As mentioned there are straight flute carbide drills specifically for hardened steels up to 65Rc. As for coolant either nothing or flood, dabbing with a brush or the odd squirt is useless.

Andrew

If it's just one or two small'ish holes I've had some success with cheapo spear-point tile drills.

I've drilled HSS this way but it needs quite a lot of pressure to cut and so Andrew's comments about coolant would seem appropriate - small dabs are unlikely to do much.

Jon

If you decide to use a Solid Carbide drill then you should be aware that they really need a rigid set up and won't tolerate a ANY flex, if there is flex then result "broken drill bit " I have a few Titex carbide ones, very spendy but very, very good, Any good Carbide drill will do the job, just bear in mind the rigidity issue

Stellite drills are another method for steels above 50Rc . They actually melt their way through rather than cut., still spendy though.

In one of Guy Lautard's Machinist's Bedside Readers he describes the Cole Drill

The secret seems to be LOTS of pressure and slow running.

I'd just avoid working with hardened material if you could, it's a quick way to break alot of tools.

If you do decide to drill with carbide make sure you don't have any radial runout on the drill as it progresses or it will break. -Just as raymond described actually, happens more frequently than you'd like.

PS. John, that "cole" device is weird!,essentially looks like a simple drill column, i'm a little perplexed by the claims, i find using a pinion hand drill hard work, it's bizarre to imagine this being any easier.

Good on him for using a genuine jacobs in the assembly though. He's got a seriously messy workshop though, so much stuff in the photos i can't even see the bench top anymore!

Michael W

Edited By Michael Walters on 11/11/2016 13:50:52

Stellite will drill through any hardened steel. It has to be run dry at a high speed and a fair bit of pressure to create a lot of friction. Be aware that the area around the hole will be blued. Colin

I think it's untidy because it's the engine bay of a car

Regarding the use of carbide tipped masonry drills: I have done it. You do need to touch up the cutting edges on a grinder. You also need to run it very slow. The silver solder used to hold the carbide is the critical point. It does not handle heat.

If you look up one of my early posts, you will see a simple and cheap method of drilling HSS. If you need more info, just get in touch. Roy M

Roy is that this thread

http://www.model-engineer.co.uk/forums/postings.asp?th=99795&p=2

I can see you have made some drill bits bit I'm not clued up enough to understand what you did? Did you cut them out of carbide?

In the same thread was a good suggestion to use a bar and cutting paste -

I will try 1 - the glass cutting cheapo bits I have if that fails a bar and cutting paste if I can get hold of some but to get something working grinding a slot with an angle grinder will suffice.

You most likely used Stellite drills Mark but at the price these days unless it's really a special need forget it!

http://www.knighton-tools.co.uk/acatalog/STELLITE_TOOL_BITS.html

'Wolfram' is German for tungsten, so they may have been tungsten carbide?

Neil

I can buy a 5mm colbalt bit from Arc Euro

http://www.arceurotrade.co.uk/Catalogue/Cutting-Tools/Twist-Drill-Bits/Drill-Bits---Cobalt/40-55mm

While I put my order in for the milling vice so that should work I assume. it's £2 so worth a gamble at any rate - will I need a smaller bit for a pilot first though?

Men Ifr,

I can't see that you have told us what you intend to drill but the Arc drills are still only HSS, carbide is your best bet.

Tony

Find someone with an EDM machine. As Tony says it would help if you gave some idea of what you are trying to do. What thickness are you drilling through ? What diameter hole 0.5 mm ? 100 mm ?

Les

Edited By Les Jones 1 on 13/11/2016 12:12:14

Edited By Les Jones 1 on 13/11/2016 12:13:01

Men Ifr. The photo shows two stages of grinding the bit. On the right shows the first stage, grind the bit similar to a screwdriver about 1.4mm thick. Second phase is to grind the drill point angle at about 140-150 degrees. Then grind minimum back clearance. Run at about 1500 rpm. It does require a bit of effort to get it to start cutting but it works well. I have made plenty of these, and used them to drill out broken taps, and, as the other photos show, drill through part off blades and even digital callipers etc. Roy M.