Drilling steel

Clarkey

Clarkey

Clarkey

Soldato
Joined
18 Oct 2002
Posts
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So I'm attempting to drill some 10mm holes through some 6mm mild steel. It's taking for EVER though, taken like 40 mins to do one hole. I have a bunch of HSS drill bits, and they were not cheap either, really none are effective at all. Even trying to do a 3mm pilot hole is a chore and a half.

What is the secret with this? Do I simply need different drill bits? I used the same bits to drill some thinner steel and they worked ok for that.
I've read that for this kind of thing you should drill very slow, with oil, and you should see a constant spiral of swarf coming out. I've tried this and did not see this result.

Any suggestions welcome, I need 7 more of these holes and don't want to be here for the rest of my life doing it. Oh yeah, it's for a seat frame so motors related, right..
 
Are you using good quality drill bits designed for metal?

Is the drill rotating the right way (some can reverse)?
 
It's all about pressure, you cannot apply enough pressure using a hand drill.

You want to keep the temperature low (low speed if big drill bit) to avoid hardening the steel locally as this will make it really hard to drill through as it will be nearly as hard as your drill bit - and will ruin your drill bit.

With a pillar drill you will be able to absolutely plough through it.
 
Speed and pressure

40 mins sounds like you've burnt the drill bit out and just creating heat.

Loads of pressure start slowly and see if you are taking any metal away, if not vary speed and pressure. There really is no point drilling without making progress.

Did you centre punch where you want to start?
 
Clarkey said:
A handheld one. A friend has a pillar drill though which I'll try to get the use of later though, I guess it will be better.



I did, didn't make the drilling any better but the deafening noise is reduced to nothing.
Click to expand...
Did you use oil from the start? Chances are the bit is blunt already.
 
Sounds like your bits are blunt.

Resharpen your bits on a bench grinder then drill using a pillar drill. Slow speed and with plenty of pressure, maybe stick some oil on if things don't progress quickly.

I can plough through 10mm steel without issue using bits from a set of 30 I bought from screwfix for a tenner.
 
Well, I watched some youtube videos of how to sharpen the bits. Looked easy enough so fired up the old bench grinder and had a go. Drill SO much better now, and I do get the constant spirals of swarf coming out which looks cool. I think the drill motor really doesn't like it when running very slow while leaning on the bit, super hot so I'm leaving it to cool down while having a brew.
 
deafening noise = BLUNT..

Trouble now is you've been at the one hole so long you'll have work hardened the hole as well, making it even more difficult to drill.

Start on a new hole with a freshly sharpened drill bit, starting off with a pilot drill at full speed of the drill, lean on it enough that it drills without sounding like it's about to snap and you have a decent amount of swarf coming off the bit. If you have no swarf or just fine dust. STOP, you are either not leaning on it enough or the drill is blunt.
Work your way up to 10mm in 3 to 4 steps 2,6,8,10 and as you do so, slow the drill speed down.

EASY
 
Pistol drills are poor for drilling through that kind of thickness plate, no real speed control. You want a good quality drill bit, plenty of lubricant and a slowish speed (depends on drill size). chances are the pistol drill is far too fast, burnt out the drill bit and work hardened the plate. Slow and steady and keep the bit cool.

Edit: as Fuzz said above, start small and build up to 10mm.
 
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