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DRILLS

Combustion equipment depends on accurate sized orifices and drillings to control fuel and air throughput. It is essential that correctly sized gas and air jets are used in order to be sure of thermal capacity, primary aeration and consequently quality of combustion.
Many established burner designs have used imperial and M.T.D. (numbered & lettered) sized drills, so it is important that these sizes can be equated to the metric (mm) sized drills in use today.

MTD & inch Size Dia. mm. Area sq. mm.   MTD & inch Size Dia. mm. Area sq. mm.   MTD & inch Size Dia. mm. Area sq. cm.
80 0.343 0.092   31 3.048 7.298   5/16" 7.938 0.495
79 0.368 0.107   1/8" 3.175 7.918   O 8.026 0.506
1/64" 0.396 0.123   30 3.264 8.368   P 8.204 0.529
78 0.406 0.130   29 3.454 9.373   21/64" 8.334 0.546
77 0.457 0.164   28 3.569 10.004   Q 8.433 0.559
76 0.508 0.203   9/64" 3.571 10.018   R 8.611 0.582
75 0.533 0.223   27 3.658 10.509   11/32" 8.730 0.599
74 0.572 0.257   26 3.734 10.951   S 8.839 0.614
73 0.610 0.292   25 3.797 11.327   T 9.093 0.650
72 0.635 0.317   24 3.861 11.709   23/64" 9.126 0.654
71 0.660 0.343   23 3.912 12.019   U 9.347 0.686
70 0.711 0.397   5/32" 3.967 12.365   3/8" 9.525 0.713
69 0.742 0.432   22 3.988 12.492   V 9.576 0.720
68 0.762 0.456   21 4.039 12.812   W 9.804 0.755
1/32" 0.792 0.493   20 4.089 13.136   25/64" 9.921 0.773
67 0.813 0.519   19 4.216 13.965   X 10.084 0.799
66 0.838 0.552   18 4.305 14.560   Y 10.262 0.827
65 0.889 0.621   11/64" 4.366 14.975   13/32" 10.318 0.836
64 0.914 0.657   17 4.445 15.520   Z 10.490 0.864
63 0.940 0.694   16 4.496 15.877   7/16" 11.113 0.970
62 0.965 0.732   15 4.572 16.420   29/64" 11.509 1.040
61 0.991 0.771   14 4.623 16.786   15/32" 11.905 1.113
60 1.016 0.811   13 4.699 17.344   31/64" 12.301 1.189
59 1.041 0.852   3/16" 4.763 17.816   1/2" 12.700 1.267
58 1.067 0.894   12 4.801 18.103   33/64" 13.096 1.347
57 1.092 0.937   11 4.851 18.488   17/32" 13.493 1.430
56 1.181 1.096   10 4.915 18.975   35/64" 13.889 1.515
3/64" 1.191 1.114   9 4.978 19.468   9/16" 14.288 1.603
55 1.321 1.370   8 5.055 20.069   37/64" 14.684 1.694
54 1.397 1.533   7 5.105 20.474   19/32" 15.080 1.786
53 1.511 1.794   13/64" 5.159 20.904   39/64" 15.476 1.881
1/16" 1.588 1.980   6 5.182 21.090   5/8" 15.875 1.980
52 1.613 2.043   5 5.220 21.401   41/64" 16.525 2.145
51 1.702 2.275   4 5.309 22.137   21/32" 16.668 2.182
50 1.778 2.483   3 5.410 22.992   43/64" 17.064 2.287
49 1.854 2.701   7/32" 5.555 24.239   11/16" 17.463 2.395
48 1.930 2.927   2 5.613 24.752   45/64" 17.859 2.505
5/64" 1.984 3.091   1 5.791 26.344   23/32" 18.255 2.618
47 1.994 3.123   A 5.944 27.749   47/64" 18.651 2.733
46 2.057 3.325   15/64" 5.951 27.820   3/4" 19.050 2.851
45 2.083 3.408   B 6.045 28.706   49/64" 19.446 2.970
44 2.184 3.748   C 6.147 29.679   25/32" 19.843 3.093
43 2.261 4.014   D 6.248 30.668   51/64" 20.239 3.217
42 2.375 4.430   E 1/4" 6.350 31.674   13/16" 20.638 3.346
3/32" 2.380 4.449   F 6.528 33.472   53/64" 21.034 3.475
41 2.438 4.670   G 6.629 34.522   27/32" 21.176 3.522
40 2.489 4.867   17/64" 6.746 35.750   55/64" 21.826 3.742
39 2.527 5.017   H 6.756 35.858   7/8" 22.225 3.880
38 2.578 5.221   I 6.909 37.493   57/64" 22.622 4.020
37 2.642 5.481   J 7.036 38.885   29/32" 23.019 4.162
36 2.705 5.748   K 7.137 40.016   59/64" 23.416 4.307
7/64" 2.776 6.054   9.32" 7.143 40.073   15/16" 23.813 4.454
35 2.794 6.132   L 7.366 42.620   61/64" 24.209 4.604
34 2.819 6.244   M 7.493 44.102   31/32" 24.606 4.756
33 2.870 6.471   "19/64""" 7.539 44.642   63/64" 25.003 4.911
32 2.946 6.819   N 7.671 46.220   1.0" 25.400 5.068

TECHNICAL SUBJECTS

» Air Heating
» Combustion
» Controls
» Fan Application Engineering
» Gas & Air Flow
» Metal Melting
» Standards

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Comtherm Limited accepts no responsibility or liability for the accuracy of information provided on this web-page. technical data and dimensions should be confirmed with the relevant Comtherm Limited Sales or Technical office.