BLUE RING: for tough and alloyed steels
Where the green ring reaches its limit, the blue one begins: high-alloy and tough steels, stainless materials and alloyed tool steels up to 1,200 N/mm². 121 versions to DIN 371, DIN 376 and JIS B-4430 in HSSE, in form B and form C, from M 3 x 0.5 to M 42 x 4.5, many sizes available bright or with a TiCN coating.
Why TiCN
The titanium carbonitride layer reaches around 3,000 HV, harder than TiN at 2,600 HV, which makes it particularly wear resistant in abrasive materials. The trade-off is lower heat resistance: TiCN coated tools need thorough and even cooling. If you cannot guarantee that, the bright version serves you better. An overview of all coatings is in the article coatings for threading tools.
Cutting speed
For unalloyed and alloyed steels up to 1,200 N/mm² the guide value is 3 to 5 m/min, for stainless and acid-resistant steels 2 to 4 m/min. Use a thread cutting oil, highly activated with special additives, or a solid lubricant. See lubricants for the range.
Form B or form C
Form B has a spiral point lead of four to five threads, carries the chips forward and belongs in through holes. Form C with a 39° spiral flute lifts them out to the rear and is the choice for blind holes. Both forms are in the BLUE RING range, along with the TwinBox pairing tap and matching drill. Other designs are among the machine taps.
The neighbouring colours
GREEN RING for unalloyed steels up to 1,000 N/mm², WHITE RING for stainless and high-alloy chromium steels, RED RING for difficult-to-machine materials above 1,200 N/mm². The full table is on the machine taps with coloured ring page.
