USEFUL DATA
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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 |
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TECHNICAL SUBJECTS
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