Precision ground metric drill bits made from M42 high speed steel bars with 8% cobalt achieving a hardness of some 63.5 - 65 Rockwell. The Cobalt allows the drill bits to hold their hardness at higher temperatures. Intended for use on alloy and hardened steels, cast iron, titanium and many other really tough, hard-to-drill, materials such as stainless steel. Perfect for home and production use. Available in a range of metric sizes. It is advisable to use coolant when appropriate.
19 July 2017
Disappointing resultsI purchased two of these to drill 20 holes in 8mm stainless steel bar. The drill bit was just 5mm, so not that large of a diameter. Working at slow speed on a drill press with constant pressure and using plenty of cutting oil, the first bit broke the cutting edge while drilling the first hole. The second bit was used to finish the first hole and broke the cutting edge on the second hole. I then used an older HSS bit to drill the remaining holes without a problem. Unlike the previous reviewer, these didn't work for me.
Red Barn Man
12 June 2017
Worth the extra costThese are little short of fantastic. Wanted to drill a number of 10mm diameter holes in 8 and 10mm steel (using a battery electric drill) over 50 in total - all achieved with just one of these drill bits and a little oil. Edges a little blunter now but will still cut without having to pilot with a smaller drill first because of the split point design. I don't think I'll ever bother with ordinary HSS drills again!