Shank, besides being a funny word, a shank is very useful. Well, what is a shank? A shank is the part of a drill bit or any other bit that you insert into a drill, router or other tool that will accept a bit. For example, take a drill bit. You have the actual drill and the actual bit itself. The shank is what the drill chuck holds onto in order for the bit to stay in place. Over the years there have been many types of shank designs. This page will cover the six most common or widely used.
The most common type of shank is the Hex Shank. A hex shank has 6 sides that are held into place by a chuck. The hex shank allows for high tourqe. While they do make different size hex shanks, the most common is the 1/4″
Another common shank is the Straight Shank. These are used a lot with router bits and drill bits. As you can see by the shaft of the bit, a shank is usually the same size as the drill bit. In regards to router bit shank sizes, the most common are 1/4″ and 1/2″. One plus about the straight shank is the acuraccy to centering. While with a hex you might get some wobbling, a straight should not wobble at all.
The next type of shank is the SDS. One of the biggest advanatges is the quick loading of these shanks. Remeber, they will not fit into any chuck, the power tool has to be able to accept these types of bits. These are more common in power tools that require hammering into hard surfaces. If you use a SDS bit you will notice that after you insert the bit into the chuck, the bit will move up and down a little. This acts like a piston, which gives the tool a better capablity of hammering.
Another type of shank is the Brace shank. While they are still produced today, they where one of the first types of shanks avaliable. How these work is they are tappered at the end, so a user can jam or insert this shank into a specific tool. There was no real way to hold the bit into place, so the harder you push the bit into the tool, the better it will stay.
The above picture is of a Morse Tappered Shank. These are primarly used in metal working. What they do is sit directly into the drill itself and are self locking. The major advange with this type of shank is very acrurate centering.
The Triangle shank is the last shank we will talk about, and it obviously has three sides. A triangle shank is just an allternative that is used in place of a hex shank for drills. While you do see this type, its not very common.