I've now got some new Gühring M35 drill bits, and the two sizes that I use mostly for mild steel (gal angle) are 6mm and 10mm, and for these two sizes I have 135° TiN coat M35 bits. I have some XDP-2000 cutting fluid, and have a squirt bottle with 1:10 fluid:water solution.

Given that I have previously not had great success with mild steel drilling (never used fluid, have blunted Cobalt bits too quickly, too much burring which was probably due to too much pressure when breaking through) I thought a quick check of my proposed technique might be in order.

My process will be:

  • Using a 10mm 135° TiN coat M35 bit, drilling through 5mm mild steel
  • Hold the job in a drill press metal working vise
  • Give the drill tip and target a squirt of fluid
  • Drill press set to 500rpm
  • Use only enough pressure to make decent progress and back off when approaching break through
  • the DP is a Nova Voyager, so I can set it to stop drilling at about 6mm, which will be just 1mm through the 5mm MS, and then I can start it up again with less pressure to try to get a cleaner hole



For the first one, I'll try it unsupported underneath to see how the breakthrough goes. Then I'll deburr both sides.

Does that sound reasonable?


Read the full thread at metalworkforums.com...