HSS drill bits V HSS co drill bits

[TrevorW]

Recently purchased a $5 HSS drill bit from Bunnings to drill through 2.5mm thick galv angle iron well lets just say ever melt the tip of the drill bit?, I did on the first use. Took it back to Bunnings and exchanged it, paid the extra $5 for a HSS Cobalt drill bit which cut through the relatively thin piece of metal like butter. What I did notice was that all the drill bits where either made in China, PRC or Vietnam. Lesson learnt don't buy cheap HSS drill bits they just don't cut it :)

[Drac0]

Did you use lubrication?
But yeah, cheap HSS drill bits are never a cheap solution except for the very, very thin metal or aluminium.

[leon]

Agreed Trevor, you need to buy high quality, I often do much drilling through steel etc and recently paid over $200.00 for a set ranging from 1mm to 10mm. at .05mm intervals.

All that stuff you see on TV about drills cutting through steel than bricks and then stainless steels is a load of crap, as the saying goes in general, you get what you pay for i guess.:shrug:

Leon:thumbsup:

[mura_gadi]

Guhring is German made, for tools, accessories etc I normally try and find German made, more often than not you can't go wrong with German made hardware.

[TrevorW]

found even the ph2 screw drivers in Ryobi or Ozito kits are next to useless as well :)

[doug mc]

As a retired fitter and turner, the quality of drill bit steel varies immensely. Same with the quality of bearings. The drill bits made in Australia, such as Sutton, are very good. Use a coolant or go slower. Toughness is just as important as hardness. Too hard they snap, too soft they blunt easily. Getting the right balance for hardened high carbon steels is an art as well as a science. Unfortunately this is one area that you get what you pay for.

[TrevorW]

where do i buy guhring in australia:thanx:

[mura_gadi]

https://www.guhring.com.au/

Licenced supplier/manufacture here in Australia, they even offer cash back for recycling your rotary bits... so the material used is of good quality.

But as mentioned, if you over heat your bits you can ruin the temper on the tips.

[ausastronomer]

When drilling steel you need to use the following:-

1) A sharp drill (which you had)
2) Cutting Oil (Lubricant) when the steel is thicker than about .8mm
3) Really slow speed with reasonable down pressure.
4) A drill press really helps in drilling steel / stainless steel, because you can set the speed and control the low speed rpm. You can get it much slower with 100% speed control, which you can't get with a cordless or corded hand drill. You can also get consistent down pressure (and more of it) which helps cut a consistent 1 piece swarf. The drill press helps to the extent that if I am drilling a piece of steel / stainless steel over about 2.5mm that I can easily unbolt and take the piece to the drill press, I will do that rather than use a portable drill in situ.

I have multiple sets of drill bits and countless single drill bits. You won't find much better than Australian made Sutton, or Patience and Nicholson (P&N). Buying a few boxes of these for a couple of dollars at a garage sale is better than a tray of new Chinese bits from Bunnings. You'll probably just need a friend with a bench grinder and the know how to re-sharpen them. I also have several of the newer cobalt bits. I also have a lot of cheap Chinese drill bits. The reason I have the cheaper bits is that I use them as "sacrificial" bits. If I have to get into a tight awkward space where there is any risk of breaking the drill bit, I would rather snap a $2 bit, than a $22 bit.

With drill bits, like most things in life you get what you pay for. The 2.5mm galvanised angle iron would have been galvanised mild steel. Had you followed the correct practices mentioned earlier for drilling mild steel, you would have found the $5 bits worked fine. They don't stay sharp as long, last as long and break easier. The cheap bits aren't as "forgiving" as the better quality bits and the cobalt bits.

Drilling stainless steel is even trickier. 304 stainless isn't too bad. 316 stainless can be quite tricky, if you don't know what you're doing. 316 work hardens as it gets hot, which means the faster you go the hotter the piece and the bit gets and the harder the piece becomes and the softer the bit gets. If you're not careful and use proper practices you end up with a melted munted mess. Some people will tell you that you need special bits for stainless like Cobalt and Titanium Nitride. If you were drilling it all day every day, I would agree, as the bits would last a lot longer and are slightly better for the purpose. For the occasional stainless hole HSS bits are fine. You need to go really slow, plenty of down pressure and plenty of lube. The other thing which can help drilling stainless is to sharpen the bit with a slightly shallower "lead", than you might otherwise have, but that isn't necessary for the occasional hole.

Cheers
John B

[TrevorW]

Thanks John although I didn't have an option but to drill using a cordless as the lengths of metal where 2 meters. Ok I didn't realise I'd have to use lubricant for such thin metal :)