Free-Cutting Steels for Optimum Machining Economy

Free-cutting steels for optimum machining economy

MACHINING RECOMMENDATIONS Sandvik free-cutting steels with composition, mechanical properties, sur- Sandvik Steel, part of the high, consistent quality face finish and tolerance to meet these Sandvik Group, is a leading requirements. It also means that the High precision machines are gaining international supplier of tubular increasing use in the precision engin- addi tion of free machining additives, e.g. and bar products, strip, wire and eering industry to enhance productiv- sulphur, is optimised for each Sandvik ity. However, a prerequisite for the full steel grade and thereby giving excellent welding products for a wide range utilisation of such equipment is that the and uniform machining properties without of applications. The products are material being processed has the correct jeopardising other properties. made from stainless steels and properties; special alloys based on nickel, • excellent and uniform machinability Machining expertise titanium and zirconium. • consistent quality of surface, A cost efficient machining of the different straightness and tolerances Sandvik steel grades is best performed by The Sandvik Group is a high- using modern types of tools. Sandvik offers free-cutting steels – in technology enterprise with some stainless and carbon grades – for CNC In this brochure general machining recom- 300 subsidiary companies, 34,000 machines and automatic lathes. Materials mendations are given, and in the separate that offer the optimum combination of data sheets recommendations are given employees and representation in properties to ensure the high quality of for each specific steel grade. more than 130 countries. the final product and favourable manu- The recommended tools are Sandvik Sandvik is a trademark of Sandvik AB facturing economy. Coromant cemented carbide tools or high speed steel tools from Sandvik CTT. Optimised properties Detailed recommendations of the tools The properties of the different Sandvik can be obtained from your nearest steel grades are tailored to meet the Sandvik Coromant or CTT office. demands for excellent and uniform machin ing properties and at the same time having optimised mechanical and other properties. This means that each Sandvik steel grade has optimal chemical Turning Indexable-insert tools When machining in CNC-lathes indexable inserts of the type T-MAX P or U should be chosen. Wherever possible, index- insert tools should also be used in automatic lathes. Special toolholders for automatic lathes are marketed by Sandvik Coromant. Inserts with a positive rake angle and sharp cutting edge should be chosen. For further details on cutting data, see the data sheets for each specific steel grade. For details on insert types and holding tools, see the Sandvik Coromant catalogue for turning tools, C-1000:7.

Brazed carbide turning tools Brazed turning tools are used in smaller automatic lathes. The most common types are knife tools, tangential tools, forming tools and boring tools. Coromant 196 and 196S are recommended as knife and boring tools. Grade H10, and the somewhat tougher H10F, are most suitable for precision parts and feeds below about 0.05 mm/rev. Grade R1P is recommended for heavier feeds and less favourable conditions. A rake angle of 0° is frequently used for knife and boring tools, especially in longitudinal turning automatics, depending on the tool's operating mode, and to facilitate regrinding; however, a positive rake angle of 10-15 ° can provide superior results. Brazed tangential tools and forming tools are not manufac- tured as standard but can be made to order.

For the selection of cemented carbide grades and tool grind- For cutting data, see the data sheets for each specific steel grade. ing, the same recommendations apply in the case of knife and boring tools. For further information on boring tools, see the Sandvik Coromant catalogue C-1000:7.

High-speed steel tools High-speed turning tools are used in the same application areas as brazed carbide-tipped turning tools. The primary applications are parting-off tools for large diameters, as well as forming tools and other processes in which cemented carbide tools cannot be used. Since high-speed steel is tougher than cemented carbide, a slightly larger rake angle may be used than for cemented carbide tools. Corona C60, is a conventional high-speed grade which is suitable for use for both carbon and stainless steel.

3 Parting-off and grooving Sandvik Coromant tools of type CoroCut are recommended for parting-off and grooving. Grooving for O-rings or other special profiles, see the Sandvik Coromant catalogue for turning tools, C-1000:7. For parting-off of slender stock in automatic lathes, brazed carbide tools should be used. We recommend the type 197 turning tool. Where machining conditions are unfavourable, it is advantageous to use high-speed steel tools ground as shown in the figure. Parting-off shall always be done with an ample supply of cutting fluid.

Parting with Q-Cut tools.

10°–15° 2°–3° A Grinding of high-speed steel parting-off tools. A = Top rake 10-15°, B = Clearance angle, 7-10°. B

For further details on cutting data, see the data sheets for each specific steel grade.

CoroCut 2-edge tools.

Threading Thread turning should preferably be done by using Sandvik Coromant T-MAX U-Lock threading tools and the cemented carbide grade GC1020. The appropriate number of passes for pitches of 0.5-3.0 mm are 4-10. Detailed information is available in the Sandvik Coromant catalogue for turning tools, C-1000:7. In applications where cemented carbide tools cannot be used for reasons of size, the external threading should be done with a threading die in a self- opening die head and internal threads with a tap. The rake angle should be 10-15°. Helical-fluted taps are recommended for more complex threading. The appropriate cutting speed for a particular threading opera- tion is determined by the degree of difficulty presented by the thread, the diameter, pitch and shape. Consequently, it may be necessary to resort to values outside the recommended values. However, it is important to maintain a sufficiently high cutting speed and to ensure an ample quantity of cutting fluid. If the cutting speed is too low, a built-up edge will form on the tools, resulting in scratched threads. For cutting data, see the data sheets for each specific steel grade.

4 Drilling Holes > Ø 12.7 mm Short-hole drilling with Sandvik Coromant drilling tools of type Coromant U-Drill are recommended for diameters between 12.7-58 mm. When producing holes with diameters greater than 58 mm, short-hole drilling is used up to 58 mm, followed by internal turning up to the desired final diameter.

Holes about < Ø12.7 mm Twist drills made of cemented carbide are recommended as the first choice and high-speed steel as the second choice. For high- speed steel drills a helix angle of 28° and a point angle of 118° are normally used. For very small-diameter holes, twist drills of cemented carbide is the most favourable solution. In these cases, it is normally required that both the drill and the material rotate. The hole should be cleared of chips starting at about 4 x the drill diameter. In many cases, it is sufficient to stop the feed for chip- breaking.

For cutting data, see the data sheets for each specific steel grade.

Milling Facemilling, square-shoulder facemilling and end milling Sandvik Coromant CoroMill milling cutters are recommended.

Hobbing Gears are often hobbed by the gene ra ting pro cess, instead of the indexing method. Hobs of the cemented carbide grade Coromant H10 are normally used. For short production runs hobs of high speed steel can also be used. A positive rake of 10-15° is recommended. Feeds: Generating process 0.01-0.03 mm/tooth Indexing method 0.001-0.003 mm/tooth

Slotting and slitting For slots between 5 and 112 mm the milling tool Coromant 331.31 is used. For further details on cutting data, see the data sheets for each specific steel grade. See also the Sandvik Coromant catalogue C-1100:6. For cutting data, see the data sheets for each specific steel grade.

5 Reaming Cutting fluids Both straight-fluted and helical-fluted reamers are used. The Turning in CNC and centre lathes: latter are to be preferred, since they work a great deal more Cutting emulsion of EP type. smoothly, although helical-fluted reamers are more expensive Drilling, threading, reaming and milling: and more difficult to grind. Cutting oil and/or emulsion of EP-type in combination with The bevel lead of the reamer should be about 45°, the rake additive fatty oil. angle 3-5° and the clearance angle 6-8°. Recommendations are for guidance only, and the suitability A cylindrical land with a width of 0.1-0.3 mm, depending of a material for a specific application can be confirmed only on the diameter of the reamer, is left next to the edge on the when the actual service conditions are known. clearance side. Continuous development may necessitate changes in the tech- nical data without notice. In automatic lathes, it has been found advantageous to use reamers ground to gundrill geometry. A suitable cemented carbide grade is Coromant H10.

Knurling For knurling with knurls of tool steel, a peripheral steel corre- sponding to the cutting speed for turning with high-speed steel is recommended. Feed, radial about 0.01 mm/rev. axial about 0.02 mm/rev.

Tolerances Drawn condition Ground condition

Diameter Diameter tolerance Ovality Diameter Diameter tolerance D1 +/- D2 +/- D3 +/- D4 +/- for D4 h7 h8 h9 h10 h11 mm mm mm mm mm mm mm mm mm mm mm mm

0.05 –0.125 0.007 0.004 0.002 >1–3 +0/-0.010 +0/-0.014 +0/-0.025 +0/-0.040 +0/-0.066

0.125 –0.25 0.009 0.005 0.003 >3–6 +0/-0.012 +0/-0.018 +0/-0.030 +0/-0.048 +0/-0.075

0.25 –0.50 0.011 0.007 0.004 0.003 0.002 >6–10 +0/-0.015 +0/-0.022 +0/-0.036 +0/-0.058 +0/-0.090

0.50 –1.0 0.014 0.009 0.005 0.003 0.002 >10–18 +0/-0.018 +0/-0.027 +0/-0.043 +0/-0.070 +0/-0.110

1.0 –1.60 0.018 0.011 0.006 0.004 0.002 >18–30 +0/-0.021 +0/-0.033 +0/-0.052 +0/-0.084 +0/-0.130

1.6 –2.5 0.023 0.014 0.008 0.005 0.003 >30–50 +0/-0.025 +0/-0.039 +0/-0.062 +0/-0.100 +0/-0.160

2.5 –4.0 0.030 0.018 0.010 >50–80 +0/-0.030 +0/-0.046 +0/-0.074 +0/-0.120 +0/-0.190

4.0 –6.30 0.038 0.022 0.013 Ground material is delivered with ISO tolerance class h7, h8 or h9 for diameters 6.30 –10.00 0.048 0.028 up to 13 mm, depending on steel grade. Please refer to the data sheets, for each specific steel grade. 10.00 –16.00 0.060

6 Conversion – hardness and tensile strength

BRINELL ROCKWELL TENSILE STRENGTH MPa Approximate conversion between hardness values and tensile strength for unalloyed and low-alloyed steels of all orked orked types. Conversion between VICKERSHV SteelHB ball SteelHRB ball DiamondHRC cone Annealed Cold 0.5%w C Cold 1.0%w C Hardened VICKERSHV hardness values is based on 940 68.0 940 SS 11 25 00 and ASTM E 920 67.5 920 900 67.0 900 140-77. 880 66.4 880 860 65.9 860 840 65.3 840 820 64.7 820 800 64.0 800 780 63.3 780 760 62.5 760 740 61.8 740 720 61.0 720 700 60.1 700 680 59.2 2350 680 660 58.3 2280 660 640 57.3 2200 640 620 56.3 2120 620 600 55.2 2040 600 580 54.1 1960 580 560 53.0 1890 560 540 51.7 1820 540 520 50.5 1750 520 500 49.1 1670 500 480 47.7 1590 480 460 437 46.1 1520 460 440 418 44.5 1450 440 420 399 42.7 1380 420 400 380 40.8 1310 400 380 361 38.8 1250 380 360 342 36.6 1200 1180 360 340 323 34.4 1120 1110 340 320 304 32.2 1060 1030 1040 320 300 285 29.8 980 950 970 300 280 266 27.1 860 900 860 900 280 260 247 24.0 800 810 780 830 260 240 228 20.3 750 740 710 240 220 209 95.5 690 650 620 220 200 190 91.8 630 570 540 200 180 171 87.3 570 490 180 160 152 82.1 510 400 160 140 133 75.1 450 140 120 114 67.0 390 120 100 330 100

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S-245-ENG Jan 2000. Production: Sanmedia. Printed by Sandvikens Tryckeri, Sweden.