T. O. 1-1A-9
2-92. Cutters for Milling. High speed tool steel is used for most milling on stainless. The other grades are used under
certain conditions, such as cemented carbides; however, capacity of equipment and cost of tooling for specific uses
requires consideration.
2-93. All the standard cutter designs used for cutting carbon steel can be used to cut stainless but preferred design is
those with helical (spiral) teeth. The use of helical cutter minimizes vibration and chatter especially when cutter/cut
exceeds 1 inch. Chip removal and loading of cutter can be aided when milling slots by staggering teeth to cut
successively on alternate sides and half the bottom.
2-94. Cutter lands should be ground to narrow width (0.020 to 0.025) with clearance (3°-10° primary angular) behind
cutting lip to reduce frictional heat resulting from rubbing. The exact amounts the land is ground will depend on diameter
of cutter, material hardness, grade, etc. However, in grinding the lands, care should be taken to avoid unnecessary
weakening of support for cutting edge. As a further measure against rubbing, a secondary clearance of 60-120 starting at
the back of the land is recommended. On side cutter, angular clearance of 30 to 10° to avoid frictional heat and rubbing
is recommended.
CAUTION
Before starting operation/equipment, carefully check for proper set up, safety, rigid support of
work and cutters, running condition of equipment, and flow of coolant/lubrication. Once
cutting is started, it should be carried to completion to avoid the effects of changes in metal
temperature. Naturally the continuous operation will depend on satisfactory operation of
equipment and other factors.
2-95. The recommended cutting speeds, tools, angles, and feeds for milling are cited in tables 2-10 and 2-11. The
information in these tables is only provided as a starting point, or as a guide.
TABLE 2-10. SUGGESTED MILLING CUTTING SPEEDS AND FEEDS.
FEED INCH
SPEED
ALLOY TYPE/GRADE
1/
SFPM
TOOL MATERIAL
301, 302, 304, 309,
0.002-0.005
35-70
High Speed Steel
310, 314, 316, 321,
347, 17-4PH, 17-7PH,
420, 431, 440, 442,
0.002-0.007
30-95
High Speed Steel
446
403-410, 430
0.002-0.008
35-90
High Speed Steel
440F
0.002-0.008
35-70
High Speed Steel
303
0.002-0.008
50-100
High Speed Steel
430F, 416
0.002-0.006
50-130
High Speed Steel
420F
0.002-0.006
35-80
High Speed Steel
1/ Use heavy feeds for rough cuts and light feeds for finishing.
TABLE 2-11. SUGGESTED TOOL ANGLES - MILLING.
TOOL MATERIAL
TOOL ANGLES
HIGH SPEED STEEL
CEMENTED CARBIDE/C
ALLOY
Rake Radial g
10o-20o
Use lower angle
Rake Axial A/
30o-50o
Use lower angle
Clearance
4o-8°
Approximately same
Land Width
1/64"-1/16"
Approximately same
1/ Saws, form relieved cutters, and miscellaneous profile cutters, etc. , are
sometimes used with rake angle as low as 0 degrees.
2-74
