September 14, 2016
By Gilbert VandenHeuvel
I’d like to teach you a little about drill bits. That may seem boring, so I’ll keep it to the point.
There are lots of different kinds of drill bits for many different jobs. Today we are going to concentrate on drill bits for metal, Twist Drill Bits, like the one in the picture above.
History of Twist drill bits
The twist drill bit is the type produced in largest quantity today. The twist drill bit was invented by Steven A. Morse of East Bridgewater, Massachusetts in 1861. The original method of manufacture was to cut two grooves in opposite sides of a round bar, then to twist the bar (giving the tool its name) to produce the helical flutes. Nowadays, the drill bit is usually made by rotating the bar while moving it past a grinding wheel to cut the flutes in the same manner as cutting helical gears.
The geometry and sharpening of the cutting edges is crucial to the performance of the bit. Small bits that become blunt are often discarded because sharpening them correctly is difficult and they are cheap to replace. For larger bits, special grinding jigs are available. A special tool grinder is available for sharpening or reshaping cutting surfaces on twist drill bits in order to optimize the bit for a particular material.
With the proper technique and some practice, bits can be sharpened on a bench grinder too. Click HERE to watch “how-to” video and always wear safety equipment.
It’s all about the Point Angle
Different versions of the twist drill bit are available to suit particular machinery and particular materials to be cut. Twist drill bits are available in the widest choice of tooling materials. However, even for industrial users, most holes are drilled with standard high speed steel bits. Here at Dwyer Mfg we work with a lot of stainless steel which is much harder then regular mild steel. We sell the same bits we use every day, Walter High Performance bits, model: SST+ .
A more aggressive angle, such as 90 degrees, is suited for very soft plastics and other materials; it would wear rapidly in hard materials. Such a bit is generally self-starting and can cut very quickly.
A shallower angle, such as 135 or 150 degrees, is suited for drilling steels and other tougher materials. This style of bit may requires a starter hole or the use of a center punch, but does not bind or suffer premature wear so long as a suitable feed rate is used. When drilling stainless steel it’s best to use strong pressure and low rpm to reduce heat with maximum cutting. Click HERE for detailed info on Walter’s 135 degree bits.
Dwyer Mfg prides itself on being able to offer quality bits for the lowest price around. Link to our web-store for pricing. With a good inventory, we can either ship or have the sizes you need ready for pick up.
Credits to Wikipedia (LINK HERE)