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Boring Tools and their Makers


 
  "Mephisto" Bits - How They Are Made - American Machinist,
Vol. 2, January 1, 1920.
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The manufacture of auger bits is one of the oldest of the tool industries in this country.

 

 

Photo courtesy of the
Great Planes Trading Company

Many of the factories have remained in the families of their founders for generations and, as is usual in such cases, radical improvements in either the product or the processes of manufacture have been slow. The bit described in this article has been improved, not by adding anything to it but by taking something from it.

Some of the processes in its manufacture are different from those generally used in bit making. Boring is only whittling in a circle and just as one uses only one blade with which to whittle so it is only necessary to have one cutting blade on an auger bit. Likewise, it is only necessary to have one scoring lip to cut off the chip.

The steel used in the auger bits made by the W. A. Ives Manufacturing Co., Wallingford, Conn., is made to its own specifications using genuine Swedish pig as a base. It has a slightly higher content of manganese than of carbon, to give stiffness; while for the endurance of cutting edges, a trace of tungsten is added.

The blanks for the bits are sheared from a flat bar of suitable size, and after being heated the shanks are drawn out and the squares formed in dies in high-speed Bradley hammers as may be seen in Fig. 1.

Fig. 1 Forging the shank.

Next, the blade is die forged in the same type of hammer. In this operation, known as plating, the blade is left thicker at the center than at the edges, the shape being similar to that of a slitting or feather-edge file.

This shape is not carried out to the extreme end, a blank space about twice as long as the width of the blade being left for drop forging the leader-screw blank and scoring lip and to leave enough thickness of metal for forming the cutting lip.

The appearance of this end after drop forging may be seen in Fig. 2, in which A is the blank for the leader screw, B the scoring lip and C the part from which the cutting lip is upset.

Fig. 2 - The drop-forged head.

It will be noted that an unusually large flash is left from the drop-forging operation. This is to ensure the maximum compression of metal at the vital part of the bit and to make certain that any accidental overheating of the metal at the edges and the extreme end will not affect the cutting parts. Trimming off the flash is done in an ordinary punching machine provided with suitable dies.

The appearance of the bit blank after it has gone through the operations described is shown in Fig. 3.

Fig. 3 - Operation before twisting.

A is the blank as cut off by the shears; B has the shank drawn out and the square formed; C shows the blade after plating. Here the thickened center and the flat at the end left for drop-forging may be seen. D shows the result of the drop-forging operation, and E represents the appearance after the flash has been trimmed.


 
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