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Technical Section - General
Hardness Conversion Table
Rockwell Hardness
Brinell
Tensile
Strength
C B A Hardness (Lbs./Sq.In.)
70 — 86.5 780 —
69 — 86.0 762 —
68 — 85.5 745 —
67 — 85.0 728 —
66 — 84.5 712 —
65 — 84.0 697 —
64 — 83.5 682 —
63 — 83.0 668 —
62 — 82.5 653 —
61 — 82.0 640 —
60 — 81.0 627 314,000
59 — 80.5 614 307,000
58 — 80.0 601 299,000
57 — 79.5 578 291,000
56 — 79.0 567 284,000
55 — 78.5 555 277,000
54 — 78.0 545 270,000
53 — 77.5 534 263,000
52 — 77.0 514 256,000
51 — 76.5 505 250,000
50 — 76.0 495 243,000
49 — 75.5 477 236,000
48 — 75.0 469 230,000
47 — 74.0 461 223,000
46 115 73.5 444 217,000
45 115 73.0 429 211,000
44 114 72.5 415 205,000
43 114 72.0 408 200,000
42 113 71.5 401 195,000
41 112 71.0 388 188,000
40 112 70.5 375 182,000
39 111 70.0 369 176,000
Lubricants
Lubricants or coolants are used on cutting tools to reduce friction or to
reduce heat.
Type of
Lubricant
Emulsion
Minimal
lubrication
Oil
Dry /
compressed
air
Description Advantages Disadvantages
Emulsions or water-soluble
cutting oils give lubrication
properties combined with
good cooling property. The
oil concentrate in emulsion
contains additives that give
different properties like
lubricators, preservatives
and EP additives to improve
bearing strength.
Minimal lubrication is a
small amount of oil
distributed with compressed
air to lubricate the cutting or
forming process.
Cutting oils have good
lubrication properties but do
not provide such good
cooling as water-based
cutting fluids.
Compressed air directed to
the cutting process.
Reduces heat.
Flushes away
chips.
Low cost.
Good
Good
Clean process.
Remove Chips.
Low cost.
Disposal cost.
Environment
Bad chip
removal.
Requires good
set up of nozzle
positioning
High cost.
Environment.
Works in a
limited no. of
applications.
Rockwell Hardness Brinell
Tensile
Strength
C B A Hardness (Lbs./Sq.In.)
38 110 69.5 363 171,000
37
36
110
109
69.0
68.5
352
341
167,000
162,000
35 109 68.0 331 158,000
34 108 67.5 321 153,000
33 108 67.0 311 148,000
32 107 66.5 302 144,000
31 106 66.0 293 140,000
30 105 65.5 285 136,000
29 104 65.0 277 133,000
28 104 64.5 269 131,000
27 103 64.0 265 130,000
26 103 63.5 262 128,000
25 102 63.0 255 125,000
24 102 62.5 248 122,000
23 101 62.0 241 119,000
22 100 61.5 235 116,000
21 99 61.0 229 113,000
20 98 60.0 223 110,000
19 97 59.5 220 108,000
18 97 59.0 217 107,000
17 96 58.0 212 104,000
16 96 57.5 207 101,000
15 95 57.0 202 99,000
14 94 56.5 200 98,000
13 93 56.0 197 97,000
12 92 55.5 192 95,000
11 92 55.0 189 94,000
10 91 54.0 187 93,000
9 90 53.5 183 91,000
8 89 53.0 179 89,000
7 88 52.5 174 87,000
Types Of Chips
Chip formation is mostly caused by plastic deformation. This
process, due to the friction generated during machining, generates
heat. Heat has the positive effect of increasing the plasticity of the
workpiece material, but the negative effect of increasing the wear on
the tool. When workpiece material reaches its breakage point, then
the chip is generated. Its form and development depend on different
factors, such as:
• Chemical-physical compatibility between tool and workpiece
materials
• Cutting operation
• Cutting conditions (speed, feed, material removal rate)
• Tool geometry
• Friction coefficient (with or without coating)
• Lubrication
Depending on different combinations of the above mentioned factors,
the chips can turn out in many different ways (see figure below).
1 Ribbon chips
2-3 Snarled chips
4-6 Washer-type chips
7 Arc chips
8-9 Element chips
Chips that are shaped as small “6’s & 9’s” are desireable in most
machining applications. this will allow for the best possible chip
evacuation from the deepest cavities. Tool life is also increased
dramatically when chips are kept small and manageable. When the
heat generated from cutting is kept in the chip instead of the tool,
wear is kept to minimum.
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