DRILLING INTO STEEL

[Deleted member 174758]

What I often find with the young joiners we get is that when you ask them to drill steel (for example to fix a timber connection piece to an RSJ) many invariably don't understand the need to centre punch the hole first, drill the hole in stages (e.g. 4mm, 8mm, 10.5mm), use a lubricant (cutting fluid, 3-in-1 or even WD40 at a pinch) and reduce the drill speed. When you get up to 10mm or so reducing the speed to between 500 and 1000rpm reduces the tendency of the drill bits to burn out and blunt too quickly or to "skate" and not cut well.

Another point to bear in mind is that whilst M2 grade (HSS) twist drills work on many lower grade steels and cast iron, they can be less than useless when attempting to drill electro-arc steels (made from scrap) such as that found in modern structural steels used in buildings (e.g. RSJ and UBs). For those I find you need to go to M42 HSS steel twist drills (also called "cobalt steel twist drills")

 

[lostinthelight]

Not unknown, depending on the type of steel for “work hardening” to take place . As JAK suggests , cobalt bit .
If your ok on a grindstone you could try changing the angle on the bit so its slightly more pointed and more likely to stay in the pilot hole
Edit: the old bit not the cobalt one

 

[^woody^]

Clamp another piece of material overr the hole, wood or suchlike, and drill through this first and it will act as a guide to stop the bit bouncing.

 

[gonch69]

I Use a bi metal hole saw on beams if not drilled for bolts its alot quicker and you only do it once

 

[Nicetoseeyoutoseeyounice]

All done, thanks to everyone for all your tips, I only have a single speed drill, as after I’d no pressure with the very small bit starting me off, then the 8mm zipped right though, I decided it was easier to just purchase some 8mm bolts and not continue with the 10mm as I’d hoped. Don’t know why, I did spray some WD40, but it all went good and now onto stage 2 of my project.
Thank you all once again.

 

[Deleted member 174758]

I Use a bi metal hole saw on beams if not drilled for bolts its alot quicker and you only do it once

Can you get them as small as 8 or 10mm, though? Smallest I can recall seeing (at least with a pilot drill, so it can be used without the need for a pillar drill or a mag drill) was 16mm

 

[catlad]

I have a 16 mm one I use for polycarbanate , I wasn't aware there was any smaller?