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Bit torque |
Bit torque as a percentage |
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Drill bit size |
O.D. |
I.D. |
Core area |
Bit area |
mean bit radius |
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factor |
of BQ bit torque |
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LTK 48 |
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1.890 |
1.390 |
1.517 |
1.287 |
0.820 |
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1.056 |
40 |
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AQTK |
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1.890 |
1.202 |
1.134 |
1.670 |
0.773 |
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1.291 |
49 |
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ATW |
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1.890 |
1.185 |
1.102 |
1.702 |
0.769 |
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1.308 |
50 |
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AQ |
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1.890 |
1.062 |
0.885 |
1.919 |
0.738 |
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1.416 |
54 |
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BTW |
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2.360 |
1.645 |
2.124 |
2.248 |
1.001 |
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2.251 |
86 |
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BQTK |
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2.360 |
1.601 |
2.012 |
2.360 |
0.990 |
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2.337 |
89 |
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BQ |
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2.360 |
1.432 |
1.610 |
2.762 |
0.948 |
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2.619 |
100 |
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NTW |
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2.980 |
2.205 |
3.817 |
3.154 |
1.296 |
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4.089 |
156 |
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NQ2 |
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2.980 |
2.000 |
3.140 |
3.831 |
1.245 |
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4.770 |
182 |
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NQ |
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2.980 |
1.875 |
2.760 |
4.211 |
1.214 |
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5.112 |
195 |
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HTW |
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3.782 |
2.792 |
6.119 |
5.109 |
1.644 |
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8.397 |
321 |
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HQ |
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3.782 |
2.500 |
4.906 |
6.322 |
1.571 |
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9.929 |
379 |
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PQ |
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4.827 |
3.345 |
8.783 |
9.507 |
2.043 |
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19.423 |
742 |
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The assumption is that the force on the bit would be in proportion
to the area of the bit |
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in that way the torque to turn the bit would be effected by the bit
area, and the |
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diameter of the bit. The diameter used to calculate the torque
constant is the diameter |
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mid way between the outside, and inside of the kerf of the bit. |
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From this chart in is predicted that the bit torque for an AQ bit
would be half what is required |
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for a BQ bit. An NQ bit would require about double what a BQ bit
requires, and an HQ bit is |
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almost double and NQ bit. |
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This is about the same as what I would have guessed from
experience. |
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On a machine like a Hydracore 2000 with a variable displacement
motor or many other machines |
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with gear boxes, the only way to get this extra torque is to slow
the rotation speed down, either |
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by gearing down or increasing the motor displacement. This chart
gives a rough idea how much |
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to slow down. |
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One this chart also is listed the bit area, in square inches, which
can give you an idea how |
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much harder you have to push on the different sized bits. Also the
core area is a usefull |
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measurement so that you can determine the sample size. |
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Nigel Spaxman |
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