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When I visited the Machine Shop near me the owner advised me that when using a drill I should turn the speed as slow as possible and press as hard as I dare. He said good cutting is when the metal is coming off in chunks.

I've tried to use this idea when using my drill press. I've selected the slowest speed and I applied lots of pressure. I tried to use lubricant spray to cool.

I succeeded in blunting two drills and melting the metal so I've hardened it.

A quick search on Google says I shouldn't be pressing hard and with drawing to allow the drill to cool?

It's been many years since I took O Level Engineering. What is the correct method?

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Slow for large drills, fast for small. Other than that just press hard enough to let the drill do the cutting. I wouldn’t try and push it through!

What Gary says, don't think ever really put much more pressure on other than the weight of my arm and that's with my crap drill press and usually blunt drill bits.

Have you got the belt in a figure of 8 so it's going in reverse?

Make sure you use good quality bits.Ive boxfuls of junk bits that blunt after one cut,and still use bits from the 60s that take a nice sharpening.
The best Ive found is from UK drills on Ebay.Really good quality.

Thank you everyone. I will try again this weekend

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To be honest I think anything up to about 7-8mm I tend to leave it at the same speed.

Quality of drill bits varies massively, even perceived top brands. I have various stuff but mostly Dormer which are OK and some random stuff from my old mans which he has sharpened multiple times, they work really well. Some of the best drill bits I have for hardened metal cutting are modified masonry drill bits that my Dad shaped/sharpened to perform on metal.

Hi Neil. You haven't mentioned what you are trying to drill a hole in? Mild Steel plate? Have you remembered that you need to centre punch first, then open the hole out in small increments? I usually start with something like 4mm, for a pilot hole, then follow up with 6mm then 8mm but it all depends on how hard the material is. Small drills can go faster, and bigger ones slower, and its usually better to press harder, and go slower than you would think, but as usual, it depends what you mean by harder and slower! How accurate do you want to go? Always check the diameter of the drill with a caliper, as occasionally, drills aren't accurately marked. Proper engineering often calls for the finished hole to be reamed to size.

I'm drilling holes in the bummer brackets for my 356. I used a 3 or 4mm drill first and then a 9mm. I was using WD-40 to cool. The first couple of holes worked but them I completed over heated

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neilbardsley wrote:I'm drilling holes in the bummer brackets for my 356. I used a 3 or 4mm drill first and then a 9mm. I was using WD-40 to cool. The first couple of holes worked but them I completed over heated

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Those Bummer brackets can be tough

They can, lot's of lube usually does the trick

You must never go in with a dry drill bit!

I reckon your tool is blunt and rounded.

Also, ensure your work area is thoroughly cleaned beforehand. The last thing you want is any waste ending up in your eye - but as this isn't something you're doing regularly I should imagine you're wearing PPE?

Weight of your arm is about right imho. Anything over 1/2" or so needs special care.

Swarf coming off is a good indicator of optimum cutting and so is the noise!
Harsh drilling noise, screams etc and you are pushing too hard. Alum will drill with a near continuous swarf, brass always chips off, and steel can behave in many ways depens on the speeds iirc.

Been a very long time since I did quite a study at college on cutting speeds, lube, tool angles etc, a complex subject.

My apprenticeship was in heavy rolling mills and suchlike, and a small hole was about 2" up. That took some nerve to use.

Use your common sense, the action will tall you if it is going well, experience counts for everything.

Same here: just weight of the arm.

I find that Bosch Professional bits are both good value (especially in packs of 5 or 10 from Amazon etc.), cut really well, and last ages compared to the ones that you can get online from UK Drills and the like...

Its the torque of the machine and the sharpness and hardness of the bit that determines the optimum speed and heat generated.

If the bit is dull (doesnt bite), it doesnt matter how fast you go, you will just create heat.

If the bit is sharp and hard, and the machine/drill has sufficient torque, you can go as fact as you like and apply as much force as you can or as much as the bit can take before bending enough to snap, but faster equals more heat.... coolant enables you to go faster.

Mild or harder steel tends to make a horrible squeeking noise when you press to hard.

I have only ever used coolant on copper, which heats extremely quickly and becomes 'sticky' when drilled or milled. Never used coolant on steel - just go slower with a sharp bit - it should cut like toffee or the bit is too dull. I know that our CNC guys use coolant on everything, but that's a different game....

Wd40 is not cutting fluid.
A drop of engine oil is better if you don’t have proper cutting fluid.