Drilling in Metal

[John G]

I'm about to drill some 5mm holes through some 16mm steel, and I want to ask the following questions:

1) Lubricant
Do you need to use a cooling lubricant when you are drilling through 16mm steel? Is any sort of oil OK (ie normal hobby oil/motor oil), or does it have to be a special lubricating oil?

2) Pilot hole a
Is it recommended to drill a pilot hole through the steel? If there is no pilot hole, isn't the drill bit tip doing a lot of work? (by "tip", I mean the 1/2mm tip between the flutes (or whatever the hell it's called), not the whole 5mm tip). If I didn't care about my drill bits, I would think no, but is it a good idea?

3) Pilot hole b
Last time I did any serious metalwork (school), we had these small, stubby pilot hole drill bits. They were about 1/16th, and very short, which tapered to a thicker body. Because they were so short the drill tip did not wander, and therefore you got very accurate pilot holes for your larger drill bit. Does anyone still use these, and where can you buy them from?

[DanP]

John,

Simply, No, no, and don't know.

You have no need for lubrication on 5mm holes but if you do want to use it, get cutting oil, might keep your drill bit sharper for longer (minimally). If the bit starts to get hot from continuous drilling just dip it in water to cool it.

Pilot hole for a 5mm drill bit would be very small. You really have no need for pilot holes when drilling 5mm.

Make sure you have your drill speed right and don't try to push the bit through the steel, let it cut it's way through. You know you're doing it right when you get a nice spiral swarf coming off both cutting edges of the bit. If this is not happening then:

You are running the drill too fast or slow. (Faster is probably better with a bit this small)

Sharpen the bit. PROPERLY. Dont just grind some off both sides. They must be even, of the same angles etc. Preferably, do it in a drill press. Much more control over everything.

Have fun,

Dan

[gatiep]

John

Those drills you mentioned are used commonly in metal machine shops. It is used as a centre drill when drilling into bar stock in a metal lathe, where the centre dril is held in the tailstock chuck. They are handy to line up larger drills or to make an indentation for the tailstocki centre to line up in.

Cya
Joe

[John G]

Thanks Joe,

The lathe story sounds familiar.

So where can you get them from? I haven't seen them in any Carbatec catalogue...

[gatiep]

L&T Venebles, Atkins Carlyle and Blackwoods in WA , not sure about the other states