Locomotive Taper Reamers.

- Taper reamers for locomotive work are generally made in two styles, with squared and with taper shanks. The commonly accepted standard taper for these reamers is 18 inch per foot. The fluted part of taper shank reamers is made the same as for those with squared shanks, the over-all length, of course, depending on the Morse taper shank used, which is the same for corresponding sizes as for chucking reamers. The size is measured at the extreme point.

Dimensions of Locomotive Taper Reamers with Squared Shank

Twist drills 1⁄4 inch in diameter and larger are made with either straight or taper shanks. The taper of the shank is almost always the Morse standard. A short neck is provided between the grooved portion and the shank. Smaller sizes of drills are, in nearly all cases, made with straight shank only, and have no neck. The lead of the helix of the groove is either the same for the full length of the groove (constant angle drills), or the lead is gradually increased from the point towards the shank (increased twist drills). For constant-angle drills the lead of the helix is usually from 6.5 to 7 times the diameter of the drill. For increased-twist drills the lead at the point is 6 times the drill diameter, and increases at such a rate that

the first turn of the helix is made in a distance equal to 7 times the drill diameter. The inclusive angle of the cutting point is 118 degrees; that is, the cutting edge makes an angle of 59 degrees with the center line of the drill. The thickness of the web or central portion between the bottom of the grooves usually increases from the point towards the shank. The increase is at the rate of 0.010 inch per inch for drills larger than 1⁄2 inch, and at the rate of 0.013 inch per inch for smaller sizes. The space between the grooves and the width of the grooves should be equal. All drills larger than No. 60 wire gage are backed off or relieved. Smaller sizes are usually not relieved. The cylindrical part or barrel of the drill is ground slightly tapered from the point towards the shank, the largest diameter being at the point. This taper is from 0.006 to 0.010 inch per foot. Straight shank drills, 3% inch in diameter and less are usually not ground after hardening. Larger sizes of straight shank drills and all taper shank drills are ground after hardening. From 0.010 to 0.015 inch should be allowed for grinding on carbon steel drills, and from 0.020 to 0.025 inch on high-speed steel drills. The temperatures to which drills are drawn after hardening are for carbon steel drills about as follows: Wire gage sizes Nos. 80-67, 480 degrees F.; Nos. 66-57, 470 degrees F.; Nos. 56–31, 460 degrees F.; Nos. 30-1, 450 degrees F.; 14-24 inch, 440 degrees F.; %-44 inch, 435 degrees F.; -11⁄2 inch, 425 degrees F.; 1-2 inches, 415 degrees F.; 2 inches and over, 410 degrees F. High-speed steel drills are drawn to from 500 to 600 degrees F. The accompanying tables give dimensions for twist drills and drill fluting cutters.

Dimensions of Twist Drills and Grooving Cutters-Wire Gage Sizes
See illustrations with table on opposite page.

0.013 0.008 0.011 0.007 0.018 0.011 0.014 0.010 0.022 0.015 0.017 0.012 0.027 0.017 0.021 0.015 0.030 0.019 0.025 0.018 0.033 0.022 0.028 0.020| 0.043 0.027 0.035 0.025 0.055 0.035 0.046 0.032 0.064 0.041 0.053 0.037 0.073 0.047 0.061 0.012 0.081 0.052 0.068 0.047 0.088 0.055 0.0731 0.051 0.101 0.065 0.085 0.059 0.116 0.075 0.097 0.068

0.124 0.081 0.104 0.073 0.133 0.087 0.112 0.079 0.143 0.094 0.119 0.085 0.152 0.100 0.128 0.090 0.160 0.105 0.135 0.096

0.173 0.114 0.146 0.103 0.187 0.123 0.157 0.111

416

4

4

5/16

63%

I

48

44

4%

5%

2 54

6%

6%

7/16

0.038 0.040 0.017 0.200 0.131 0.168 0.119 0.042 0.045 0.019 0.225 0.147 0.189 0.133 0.045 0.050 0.021 0.250 0.164 0.211 0.148 0.048 0.050 0.023 0.275 0.180 0.232 0.163 0.051 0.055 0.025 0.300 0.197 0.253 0.178

0.054 0.055 0.027 0.325 0.213 0.274 0.193 0.058 0.060 0.029 0.350 0.230 0.295 0.208 0.062 0.060 0.031 0.375 0.246 0.316 0.223 0.066 0.060 0.033 0.400 0.262 0.337 0.238 0.074 0.065 0.037 0.450 0.295 0.379 0.267 0.082 0.065 0.041 0.500 0.328 0.422 0.297 0.090 0.070 0.045 0.550 0.361 0.464 0.327 0.098 0.075 0.049 0.600 0.394 0.506 0.356 0.106 0.080 0.051 0.650 0.426 0.548 0.386 0.114 0.085 0.053 0.700 0.459 0.590 0.416 0.122 0.090 0.055 0.750 0.492 0.632 0.445 0.128 0.090 0.057 0.800 0.525 0.675 0.475 0.134 0.095 0.059 0.850 0.558 0.717 0.504 0.140 0.095 0.061 0.900 0.591 0.759 0.534 0.146 0.100 0.063 0.950 0.623 0.801 0.564 0.152 0.100 0.065 1.000 0.656 0.844 0.594 0.158 0.105 0.066 1.050 0.689 0.886 0.623 0. 164 0.105 0.067 1.100 0.722 0.928 0.653 95% 0.170 0.110 0.068 1.150 0.754 0.970 0.683 9% 0.176 0.110 0.069 1.200 0.788 1.012 0.713 0.188 0.115 0.071 1.300 0.853 1.097 0.772 1012 0.200 0.120 0.073 1.400 0.919 1.181 0.831 0.212 0.125 0.075 1.500 0.984 1.265 0.891 0.224 0.130 0.075 1.600 1.050 1.350 0.950 10% 0.236 0.130 0.075 1.700 1.115 1.434 1.009 104 0.244 0.135 0.075 1.800 1.181 1.518 1.069 10% 0.252 0.135 0.075 1.900 1.247 1.603 1.128 111⁄2 0.260 0.140 0.075 2.000 1.313 1.687 1.187 11% 0.268 0.145 0.080 2.100 1.378 1.772 1.247 1234 0.276 0.150 0.080 2.200 1.444 1.856| 1.306 13% 0.284 0.155 0.080 2.300 1.509 1.940 1.365 0.292 0.160 0.085 2.400 1.575 2.025 1.425

2

7

78

11/8

Twist Drill and Steel Wire Gages. The differences in the gages for small diameter twist drills and steel wire are a constant source of trouble to those who have to deal with drills and steel wire; and gage numbers mean nothing except if the name of the gage employed is specified. Some drill manufacturers are discouraging the use of gage sizes and are asking that the sizes of drills ordered be denoted in decimals of an inch. There are three well-known standards for twist drills and steel wire that are commonly used at the present time. These are the Stubs steel wire gage, the gage used by the Standard Tool Co. and the gage used by other leading manufacturers, such as the Morse Twist Drill & Machine Co., and Brown & Sharpe Mfg. Co. The latter has been termed, in the accompanying tables, "the manufacturers' standard."