Machining

Machining Guidelines

The alloys described here work harden rapidly during machining and require more power to cut than do the plain carbon steels. The metal is “gummy”, with chips that tend to be stringy and tough. Machine tools should be rigid and used to no more than 75% of their rated capacity. Both workpiece and tool should be held rigidly; tool overhand should be minimized. Rigidity is particularly important when machining titanium, as titanium has a much lower modulus of elasticity than either steel or nickel alloys. Slender work pieces of titanium tend to deflect under tool pressures causing chatter, tool rubbing and tolerance problems. 

Tooling

Make sure that tools are always sharp. Change to sharpened tools at regular intervals rather than out of necessity. Titanium chips in particular tend to gall and weld to the tool cutting edges, speeding up tool wear and failure. Remember—cutting edges, particularly throw-away inserts, are expendable. Don’t trade dollars in machine time for pennies in tool cost.

Feed rate should be high enough to ensure that the tool cutting edge is getting under the previous cut thus avoiding work-hardened zones. Slow speeds are generally required with heavy cuts. 

Lubricants

Sulfur-chlorinated petroleum oil lubricants are suggested for all alloys but titanium. Such lubricants may be thinned with paraffin oil for finish cuts at higher speeds. The tool should not ride on the work piece as this will work harden the material and result in early tool dulling or breakage.  Use an air jet directed on the tool when dry cutting, to significantly increase tool life.

Lubricants or cutting fluids for titanium should be carefully selected. Do not use fluids containing chlorine or other halogens (fluorine, bromine or iodine), in order to avoid risk of corrosion problems.

Machining Speeds

The following speeds are for single point turning operations using high speed steel tools. This information is provided as a guide to relative machineability, higher speeds are used with carbide tooling.

The machinability rating quantifies the machinability of various materials. The American Iron and Steel Institute (AISI) determined machinability ratings for a wide variety of materials by running turning tests at 180 surface feet per minute (sfpm) and arbitrarily assigned 160 Brinell B1112 steel a machinability rating of 100%. The machinability rating is determined by measuring the weighed averages of the normal cutting speed, surface finish, and tool life for each material. Machinability rating less than 100% is more difficult to machine than B1112 and material with a value more than 100% is easier.

  AlloyUNSMachinability* (Surface ft/min)Speed as a % of B1112Hardness (Nominal, HRB)Yield Strength (Min, ksi)
Nickel Alloys   RA330® N08330 35-45 24 86 30
    RA333® N06333 20-25 14 76-95 39
    RA 602 CA® N06025 20 12 - 39
    600 N06600 25-35 18 85 35
    601 N06601 25-35 18 65 30
    AL-6XN® N08367 65-75 42 90 45
    625 N06625 20 12 24 HRC 60
    617 N06617 20 12 87 49
    718 AMS 5662 N07718 20-40 18 37 HRC 70
    718 NACE / API N07718 -   32-40 HRC 120-145
    Nickel 200/201 N02200/1 170-200 112 45-75 55
    Monel 400 N04400 60-70 39 60-80 15
    Alloy 20 N08020 65 39 94 35
    K500 Annealed N05500 60 36   40
    K500 Aged N05500 25 15   85
    825 N08825 25-35 18 135-165 35
    800H/AT N08811 25-35 18 70 25
    X-750 N07750 20 12 65 123
    Waspaloy N07001 20 12 38 HRC 120
    C-276 N10276 20 12 87 41
    C-22 N06022 20 12 75-90 47
    B2 / B3 C10200 15-20 11 60-80 39
    G-30 N06030 15-20 10 90 45
    N155 R30155 15-20 11 92 57
    X N06002 20 12 96 -
    Invar 36 K93600
K93603
30-45 25 80 max 35 (Typical)
               
Super Duplex   ZERON® 100 S32760 30-65 29 32 HRC max 80
    ZERON® 100 FG (Fastener Grade) S32760 -   32 HRC max 105
Duplex   2205 S31803, S32205 50-65 35 31 HRC max 65
Lean Duplex   LDX 2101® S32101 78-106 56 31 HRC max 65
               
Austenitic   RA 253 MA® S30815 45-60 32 91 45
Stainless Steel   310 S31008, S31009 70-75 44 78 30
    309 S30908 70-75 44 83 30
    321 S32100 75 45 82 30
    347 S34700 75 45 87 30
    446 S44600 75 45 85 -
    416 Annealed S41600 170 103 27 HRC 49
    416 Hardened S41600 80 48 28 HRC  
    440C S44004 65 39 56 HRC  
    Prodec® 303 S30300 100-105 62 91 30
    Prodec® 304/304L S30400, S30403 90 55 92 30
    Prodec® 316/316L S31600, S31603 100 61 92 30
    Nitronic 50 (XM-19) S20910 20-35 17 96 55
    Nitronic 60 S21800 20-35 17 92 50
               
Precipitation   17-4 Annealed S17400 75 45 34 HRC -
Hardenable   17-4 H1150 S17400 80 48 33 HRC 125
Stainless   17-4 H1025 S17400 60 36 38 HRC 165
    17-4 HH1150 S17400 80 48 27 HRC 85
    15-5 Annealed S15500 75 45 33 HRC -
    13-8 Annealed S13800 75 45 44 HRC -
    A-286 (AMS 5737) S66286 30-35 20 31 HRC 95
    A-286 (AMS 5732) S66286 30-35 20 32 HRC 85
               
Titanium Alloys   6-4 R56400 30-40 21 - 120
    6-4 ELI R56401 30-40 21 30-34 HRC 110
    6-4 STA R56401 15-45 18 - 120-155
               
Cobalt Alloys   188 R30188 15 9 98 67
    Rene 41 N07041 12 7 33-40 HRC 115
    L605 (25) R30605 15 9 97 45
               
Carbon & Low   B1112 AISI B1112 165 100 - 120
Alloy Steels   12L14 AISI 12L14 325 197 84 60
    1215 AISI 1215 225 136 91 60
    1137 AISI 1137 135 82 88 55
    1018 AISI 1018 120 72 72 53
    1045 AISI 1045 75 45 84 45
    H11 T20811 75 45 56 HRC  
    4340 G43400 65 39 40-60 HRC 121
               
    The machining speeds are for single point turning operations using high speed steel tools. This information is provided as a guide to relative machineability, higher speeds are used with carbide tooling.