It is found that 120 to 130 such holes can be drilled before it is advisable to resharpen the twist drill.
Bore it with a twist drill, or nosebit, to the depth of an inch and a half.
But if a twist drill is ground more flat like a flat drill, it will not "grab" into the metal as it passes through.
A twist drill is made with a slight taper toward the shank end.
A hole is next drilled in the end of the rod by using a twist drill in the tailstock.
These reamers are held while in use in a socket inserted in the tailstock spindle, as when using a twist drill.
For these reasons the fluted drill or the twist drill is preferable, especially as their diameters are maintained without forging.
He had decided to tell of the lunch-box and twist drill episode, but to say nothing, for the present, of the strange white fire.
twist drill bits will bore both wood and iron, and they are not expensive up to three-eighths inch or one-half inch.
This drill will go through a wall almost as quickly as a twist drill and with much less labour.