THIS GUIDE IS OFFERED AS AN AID TO MY CUTTING TOOL BUYERS IN CHOOSING WHICH MATERIAL IS BEST SUITED FOR THEIR MACHINING OPERATIONS.

PART TWO

HIGH SPEED STEELS

THE HIGH SPEED STEELS CAN BE CLASSIFIED INTO THREE TYPES:

1. TUNGSTEN HIGH SPEED STEELS.

2. MOLYBDENUM HIGH SPEED STEELS.

3. HIGH SPEED STEELS CONTAINING COBALT.

AS A GENERAL RULE, THE TUNGSTEN GRADES SUCH AS T1, T2, ETC. ARE NOT QUITE AS TOUGH AS THE MOLYBDENUM GRADES, BUT ARE MUCH SIMPLER TO HEAT TREAT. THE MOLYBDENUM HIGH SPEED STEELS SUCH AS M1, M2, M3, M7, AND M10 ARE MUCH MORE WIDELY USED THAN THE TUNGSTEN GRADES.

BOTH THE TUNGSTEN AND THE MOLYBDENUM HIGH SPEED STEELS (TYPES 1 AND 2) ARE RECOMMENDED FOR THE MACHINING OF EASY MACHINABLE MATERIALS.

HIGH SPEED STEELS WITH COBALT (TYPE 3) CONTAIN 5 TO 12% COBALT. THIS ADDITION OF COBALT PROVIDES GREATER HOT HARDNESS AND WEAR RESISTANCE, BUT RESULTS IN A SOMEWHAT LOWER TOUGHNESS.

IN GENERAL, IT HAS BEEN FOUND THAT STEELS WITH COBALT ARE NOT PARTICULARLY ADVANTAGEOUS IN THE MACHINING OF THE READILY MACHINABLE MATERIALS. THEY ARE, HOWEVER, MOST BENEFICIAL FOR MACHINING HARDENED STEELS, AND FOR THE MORE DIFFICULT TO MACHINE METALS SUCH AS TITANIUM AND NICKEL BASE HIGH TEMPERATURE ALLOYS.