TTP HARDdrills 4mm drill bit - Pack of 10 Cobalt metal drill bits for drilling hard steel, cast iron, sheet metal & stainless, hardened heavy duty twist drills, 5% cobalt M35 jobber wood masonry

picnic comes from computer support - "problem in chair, not in computer"having struggled to remove some metal bolts and then struggled again to drill the bolts out, a little research led me to these drill bits. All the reviews suggested that they are the best.but I was drilling away and making virtually no progress and thinking "this can't be right"I'm more used to drilling wood or brick - I don't usually work with metalso - back on line - - first lesson - my drill was spinning too quickly - just left on the faster of 2 settings - so I selected the slower speed - about 400rpm. - still nothing - I'd been brought up with "let the drill do the work" but some of the videos show pressure being applied. so I lent into the drill a bit - and then - oh boy ladies and gentlemen we have swarf !so, after a frustrating couple of hours I had finally figured out how to use these and after that I drilled thru the bolt in a couple of minutes. the others followed - using the same drill bit - not fast but these are stainless steel bolts I'm drilling thru.so - a first class product - just take a moment to figure out how to use them !

Bought these to drill out broken hardened screws that had completely defeated normal HSS drill bits. With a slow drill speed, progress was immediate and multiple screws were drilled out with no perceptible deterioration in the performance of the bit. If you need to drill hard metals these bits are a revelation. I've since purchased smaller diameter bits for drilling lock wire holes in hardened bolts, which they have done with ease. Good price for what these do.

Had to drill out a few steel bolts that held bbq burners in place. Other drill bits (made from titanium!) literally snapped on contact. However, these TTP/Cobalt drills got the job done... Highly recommended... :-)

These bits save my car. I tried many tips, when I had to drill out a hardened screw out of the subframe on my car. You get 10 bits, I broke 3 , but the 4th one did the job. Any other HSS tips like bosh did not even drilled in to the hardened screw. Well done

Great drill drilled all 8 holes I needed in stainless steel extremely quickly, great value too!

Very good

great drill bit,great value

Used to drill domex with a bit of patience worked a treat.