Machine Drawing

Annexure 445

dharm
d:\N-Design\Des23-1.pm5

Table 6 Tap drill sizes

Metric coarse threads British Standard Whitworth (BSW) threads

Size Pitch Max. minor Drill size size Threads per Max. minor Drill size

(mm) (mm) diameter (mm) (inch) inch diameter (mm)

(mm) (mm)

18 2.5 15.744 15.5 1 5/8 5 35.921 35.5

20 2.5 17.744 17.5 1 3/4 5 39.096 39

22 2.5 19.744 19.5 1 7/8 4 1/2 41.648 41.5

24 3 21.252 21 2 4 1/2 44.823 44.5

27 3 24.252 24

30 3.5 26.771 26.5

33 3.5 29.771 29.5

36 4 32.270 32

39 4 35.270 35

42 4.5 37.799 37.5

Table 7 Properties and uses of irons, plain-carbon steels and alloy steels

Material and approximate Tensile strength

composition (%) (Mpa)

Typical uses

Wrought iron Fe (almost pure) 340 Chain links, ornamental work, etc.

Grey cast irons 170–350 Brackets, machine frames, pistons, cylinders,

(3-4) C, (1.2-2.8) Si, pipes, pulleys, gears, bearings, slides, etc.

(0.5-1) Mn

Malleable irons 280–510 Brake drums, levers, links, shafts, hinges,

(2-3) C, (0.1-0.5) P, spanners, chains, wheels, vice bodies, etc.

(0.5-6) S, (1-5) Si,

(0.4-2.1) Ni, (0.1-5) Cr

Spheroidal-graphite (SG) irons 370–725 Machine frames, pump bodies, pipes, crankshafts,

Nodular irons hand tools, gears dies, office equipment, etc.

Low-carbon steels 430–480 Lightly stressed parts, nails, car bodies, chains,

(up to 0.25) C rivets, wire, structural parts, etc.

Medium-carbon steels 480–620 Axles, spindles, couplings, shafts, tubes gears,

(0.25-0.6) C forgings, rails, hand tools, dies, ropes, keys, etc.

High-carbon (tool) steels 620–820 Hammers, chisels, screws, drills, taps, dies, blades,

(0.6-1.5) C punches, knives, chisels, saws, razors.

Nickel steels 310–700 Axles, crankshafts, car parts, camshafts, gears,

(0.1-4) C, (0.04-1.5) Mn, pins, pinions, etc.

(1-5) Ni

Stainless steels 650-900 Chemical plants, kitchen equipment, cutlery,

(0.05-0.1) C, (0.8-1.5) Mn, springs, circlips, etc.

(8.5-18) Ni, (12.5-18) Cr

Low-alloy nickel-chrome steels 930–1500 Highly stressed parts: conrods, shafts, gears,

(1-5) Ni, (0.6-1.5) Cr driving shafts, crankshafts, etc.

Manganese steels 700–850 Cutting tools, stone crushing jaws, dredging

(0.35-1.2) C, (1.5-12.5) Mn equipment, press tools, railway crossings, etc.

Heat-resisting steel 690 Components exposed to high temperatures, etc.

(0.1) C, (1.5) Si , (1) Mn,

(19) Cr, (1) Ni