drilling and lubricant

Have a small electric drill with a 8mm drill trying to drill through some mild steel about 7 mm thick.

The drill is pretty blunt. I'm leaning on it and making little progress.

I know the answer is to travel out and buy another drill, but out of interest; that so called 'milk' used on lathes (mixture of oil and water i believe) would that help me in this situation?

One aspect is that the drill is so hot, i'm wondering if all the temper could be taken out of it, without some coolent?

Reply to
D. T. Green
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Sharpen it? Not too difficult to improve a blunt drill in a size as big as this. A small oil stone, etc, will do it.

That is a primary reason for the cutting fluid. To keep things cool.

Also most mains electric drills will run too fast for this - which speeds up the drill getting blunt.

Reply to
Dave Plowman (News)

Just about any lubricant would have helped before the drill bit was blunt....

Reply to
Phil

D. T. Green posted this via news:jtmnb0$ovi$ snipped-for-privacy@dont-email.me:

Cutting oil is a special water-soluable oil/chemical compound... available in some formulation in some hardware stores...

If the drill bit overheats, not only is the hardening diminishing on the bit itself, but also the ferrous steel material is 'work harding' deeper proportinate to the heat as well...

A sharp high-quality appropriate bit is is your primary objective. Coolant and lubricant can be achieved with just plain water or just plain motor oil sufficiently enough for a one-off home job...

To sharpen the drill bit, use a common kitchen knife flat sharpening stone... take care to hone both the tip end (a slight but even land on both flutes) and at a careful angle, the flute surfaces... evenly.

Or, just go buy another drill bit. That'd be the easiest way.

Reply to
Bucky Breeder

A pilot drill of a few mm might make things easier.

Any fluid will help to keep the drill cool, from oil to water.

Reply to
Fredxx

The milk is water based coolant ... not that good as an aid to cutting, other than it keeps the work/tool cool.

If you are drilling MS better to use a cutting fluid ... I keep a bottle of MWF Molyslip cutting fluid by drill press for most things ...

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aluminum when I use white spirit.

If your drill is blunt ... sharpen it or replace it.

Reply to
Rick Hughes

Agree with other posters. To answer this point, if it is a cheap carbon steel drill then yes, almost certainly ruined now. High speed steel (HSS) is pretty much the norm except in "wood drill" sets, that will go up to nearly red heat without softening, so is much more tolerant of brutal treatment.

Reply to
newshound

On Or About This Date In History 7/12/2012 9:35 AM, Without Any Thought D. T. Green Pecked Out The Following:

Coolant and lubricant are not the answer. Sharpening the bit will work wonders. If you don't know how, get a new one.

Reply to
OldGringo38
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WD-40, motor oil, real cutting oil. But even using any of those is going to be a waste of time if your drill RPM is too high. Use a drill press and keep the RPM's around 800 or less. And start with a fresh quality bit.

HTH

Reply to
§ñühwö£f

I recently had to drill some 8mm diameter holes through 6mm mild steel with a HSS bits and a cheap power drill. I was expecting it to be difficult, but I found that by starting with a 3mm drill and working up in 1mm increments, it was easy.

I guess this approach might lead to the hole wandering a bit, and could cause uneven wear on the drill bits.

Reply to
RustyCrampon

The steel may be case-hardened. Get yourself a stainless steel bit rather than HSS. By 'stainless steel' I don't mean made of that metal, I mean a drill bit specially made for stainless steel.

Reply to
Aardvark

If the drill bit is 'blue' throw it out. A sharp tool is a safe tool. A new drill bit is cheap enough and will save you an injury. A drill press and decent vise would be best for the job. Investing in a drill sharpener will save time and money in the long run.

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are cheaper alternatives around.

Reply to
Parko

Aardvark wrote in news:jtn6r1$pbf$ snipped-for-privacy@dont-email.me:

Prolly a carbide tipped drill then.

Reply to
§ñühwö£f

Most of the problems with drilling are caused by speed and pressure, pressure being the main problem with non tradespersons, use as much pressure as you can with out breaking the drill, this comes with experience.

Reply to
F Murtz

"Soluble" *and* "emulsion"? Interesting concept...

Reply to
Dave Liquorice

harry is an interesting concept.

Reply to
The Natural Philosopher

Indeed, but that's the term commonly used in industry.

Reply to
Andy Dingley

Have a small electric drill with a 8mm drill trying to drill through some mild steel about 7 mm thick.

The drill is pretty blunt. I'm leaning on it and making little progress.

I know the answer is to travel out and buy another drill, but out of interest; that so called 'milk' used on lathes (mixture of oil and water i believe) would that help me in this situation?

One aspect is that the drill is so hot, i'm wondering if all the temper could be taken out of it, without some coolent?

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All the other replies have pretty much covered it, but I'd emphasise that if you've "blued" the cutting end trying to grind your way through the metal, you've ruined the temper of the steel the drills made of - otherwise I'd suggest tou get someone to teach you the art of sharpening drill bits, too late for that now - throw it away & buy a new one.

If you were drilling sheet steel I'd issue a stern warning about the danger of the drill catching as it breaks through and spinning the workpiece so it scythes through your hands - not such a risk with 7mm, but I'd heed the advice others have given to clamp the work piece on a pillar drill stand.

As for lubricants - I'm a bit stingy myself and tend to use what's to hand rather than buy expensive special products. I generally get good results with molybdenum disulphide wheel bearing grease, Slick50 or Finnish-line teflon bicycle grease.

Reply to
Ian Field

Heh. That reminds me of a job I did some twenty years or so ago in BHS in Liverpool.

We were fixing heavy galv angle (3 X 3) to a concrete soffit using Hilti fixings, then fixing hangers of the same material to this angle, using

9mm bolts.

Having fixed a couple of lengths of the angle to the soffit, we'd then clamp some hangers to the angle at 600mm centres then drill a 9mm hole through the two thicknesses of metal for the bolts. As I was having to hold the drill over my head, a big drill weighing 3kg would have been a bit too tiring on the arm (believe me, we checked this :-)) so my mate brought in a powerful little drill he had at home made by a company I'd never heard of before or since called De Souter.

It was high Summer and, as the store was still open for business, our work area was completely encapsulated in Visqueen- the thick polythene sheeting you see used on sites for all kinds of purposes. It was like a Turkish bath in there, and we were all sweating heavily the whole time we were in there.

The De Souter was a marvellous drill, plenty of power, adjustable speed and would fit nicely into the palm of my hand. Except the body was made completely of smooth, shiny steel, or perhaps aluminium. Combined with sweaty hands, it was, in retrospect, an accident waiting to happen.

While I was drilling one of these holes, increasing my grip just before the bit emerged from the other side as usual (there's always, as you said, a catch as the bit emerges), suddenly the bit caught. The torque of the drill twisted it out of my sweaty hand and the bit snapped. Not a straight snap, but a helical one, leaving part of the bit in the metal and the rest of it in a pointy corkscrew shape in the drill, which fell, bit first.

This corkscrew embedded itself in my breastbone, through skin and muscle. The whole drill was actually stuck at an oblique downward angle into my chest. My mates beside me had watched all this happening and couldn't move for laughing at the sight of me with a hand drill sticking out of my chest. I let them laugh for a minute or so and then pulled it out.

It could have been much, much worse, but the end result was a tiny, almost imperceptible hole in the middle of my chest and one drop of blood. I think the fact that the drill bit- what was left of it- was so hot it cauterised the wound. We were all pretty amazed at the outcome.

A slight throb in my breastbone for a few days, and that was it.

Reply to
Aardvark

It's the way I've done it for decades - I always use a pilot drill of

2mm or greater.
Reply to
Grimly Curmudgeon

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