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BreakingChips

Stainless · ISO P, cuts like steel

420 stainless speeds and feeds

Also: X20Cr13, 1.4021, 420S37, S42000

Starting points from the same engines as the calculators, with no tool or setup picked. The first number is where to start; the range is what the manufacturer charts allow. Open a calculator for your tool, machine and cut.

Draft data: researched from manufacturer charts, not yet reviewed by a machinist.

Annealed200 HB

Turning

CutSFMFeed, IPRDepth, in
Finishing800547–1,132244 m/min0.0070.004–0.0100.18 mm/rev0.0220.004–0.0400.6 mm
Medium673459–951205 m/min0.0140.007–0.0200.34 mm/rev0.0850.012–0.1582.2 mm
Roughing632432–894193 m/min0.0170.010–0.0240.43 mm/rev0.1490.060–0.2373.8 mm

For a CVD carbide insert, general stability, 15 min tool life.

Milling, solid carbide end mill

Speed 150 (100–250) SFM · 46 m/min

Chip load per tooth, before chip thinning
Cutter ØIPTmm/tooth
1/8"0.00030.0001–0.00040.006
1/4"0.00090.0005–0.00130.023
1/2"0.00160.0010–0.00210.039
3/4"0.00290.0028–0.00300.074
1"0.00340.0028–0.00400.086

Drilling, Ø1/2" at 3×D

DrillSFMFeed, IPR
HSS4530–710.00550.0050–0.0060
Cobalt7225–820.00550.0050–0.0060
Solid carbide, through-coolant202130–5500.00530.0050–0.0057

Feeds scale with drill Ø (0.5" here): the drilling calculator sets them for yours.

Tapping

Cut tap
42 (20–80) SFM
Form tap
28 (12–50) SFM

Hardened & tempered330 HB

Turning

CutSFMFeed, IPRDepth, in
Finishing485331–686148 m/min0.0070.004–0.0100.18 mm/rev0.0220.004–0.0400.6 mm
Medium408278–577124 m/min0.0140.007–0.0200.34 mm/rev0.0850.012–0.1582.2 mm
Roughing383262–542117 m/min0.0170.010–0.0240.43 mm/rev0.1490.060–0.2373.8 mm

For a CVD carbide insert, general stability, 15 min tool life.

Milling, solid carbide end mill

Speed 91 (61–152) SFM · 28 m/min

Chip load per tooth, before chip thinning
Cutter ØIPTmm/tooth
1/8"0.00030.0001–0.00040.006
1/4"0.00090.0005–0.00130.023
1/2"0.00160.0010–0.00210.039
3/4"0.00290.0028–0.00300.074
1"0.00340.0028–0.00400.086

Drilling, Ø1/2" at 3×D

DrillSFMFeed, IPR
HSS4530–710.00550.0050–0.0060
Cobalt7225–820.00550.0050–0.0060
Solid carbide, through-coolant202130–5500.00530.0050–0.0057

Feeds scale with drill Ø (0.5" here): the drilling calculator sets them for yours.

Tapping

Cut tap
42 (20–80) SFM
Form tap
28 (12–50) SFM

Sources