Hi all.

Deep end milling work with slender cutters in pre hardened P20 steel can really push the limits of milling....and expose issues that are not usually so apparent.

I have been cutting a mould cavity - finishing with a 1/8" end mill 21 mm deep and thought it might be useful to post what have learned - and welcome any input on this subject .

Some tricks I learned are:
  • Undercut the cutter so only the last portion in in contact with the work.
  • Lap the cutter razor sharp or use a new cutter
  • Use conservative speeds and feeds
  • Rough out with a cutter only slightly bigger than the finishing cutter so the finishing rad cut is small.
  • Take only a tiny finishing cut - in this case 0.06mm and 0.20 mm deep cuts
  • Tungsten carbide is better than HSS


Just spilled a drink on my keyboard and will have to quit early !

Cheers. Keen