When choosing drill bits it’s important to choose the right one for the job.
There are several different shank types for drill bits, but we’re going to look at just two, the straight shank and the hex shank, there are many other types like brace shank, round shank, triangle shank, but we won’t be touching on there here.
Both are useful but does a straight shank drill bit offer any benefit over a hex shank? We’re going to have a look and find out about the differences between straight shanks and hex shanks.
What Is A Straight Shank Drill Bit?
The straight shank drill bit is probably the most widely used per number and is easily recognized. The shank will frequently be the same size as the shaft which is the part that does the drilling.
It is held in the drill most often by a three jaw drill chuck. A chuck is the part of the drill that holds the bit while it is in operation. It grabs the shank of the bit and is tightened to secure it in place.
Sometimes if the drill bit is very small the shank will be bigger so that the chuck can grasp it and be tightened around it. Similarly drill bits that are quite large may have a smaller shank so that it will fit into a standard chuck.
A straight shank drill bit can also be used in a collet chuck which is more like a segmented sleeve and is more useful for smaller drill bits.
Straight shank drill bits can be used in a power drill, drill press or hand drill.
What Is A Hex Shank Drill Bit?
The hex shank drill bit has a different profile than the straight shank drill bit. This one has six sides, hence its name. These too can be held by a three jaw chuck or one that is specifically designed for hex shank bits.
With this shape of drill bit there is no need to tighten as the shank does not slip due to its shape. They are widely used and are among the most commonly used drill bits especially for harder materials that are difficult to drill.
The hex shank bit cannot be used in a drill with a regular round collet and a special collet is needed for them. This shape has much more surface contact with the drill chuck and this makes them better for use at higher torque.
Like straight shank drill bits a hex shank drill bit is available in a variety of diameters and various lengths. They are also made from different metals, combinations of metals or coated depending on their intended use.
How Do They Differ?
This question seems like it should have an obvious and straightforward answer but in reality there are a few ways other than their shape that these two drill bits differ.
The straight shank drill bit has a cylindrical profile and so it relies on friction to hold it in place via the chuck. The hex shank drill bit has no need for friction to hold it as the shape of the shank means there is no slippage.
Hex shank drill bits therefore are more suited to higher torque use than a straight shank bit. But what does that mean?
Torque is the force that the drill can produce in order to turn the drill bit. This is not the same as speed, they are two different things, but together they produce the power of the drill.
So a hex shank drill bit is capable of more force than a straight shank drill bit and so can be used for drilling through tougher materials.
Is A Straight Shank Drill Bit Better Than A Hex Shank Drill Bit?
If a hex shank therefore has more torque does a straight shank bit offer any benefit over a hex shank? Well, it turns out that torque is not everything.
When it comes to accuracy in centering, a straight shank bit will typically outperform a hex shank drill bit.
This is because the hex shank bit has a tendency to wobble as it is boring into a material. While it may only be slight is it often enough to throw the center of the drilling off. It can happen because the shank is often much smaller than the shaft of the drill bit.
A straight shank drill bit does not typically wobble. This is mainly because the shaft is more often than not the same diameter as the shaft. It is also because the shank is cylindrical and will rotate smoothly.
Another benefit of the straight shank drill bit is that it can be used in a wider range of power drills, drill presses and routers.
What Jobs Are Best Suited To Straight Shank Drill Bits?
As straight shank drill bits can be used in all standard chucks you can pretty much use these bits for anything. They’re available to use for drilling wood, metal, concrete and masonry among other things.
There are even straight shank drill bits for glass. You can also have universal bits which can be used on wood, metal or ceramic. Many of them have an extremely sharp carbide tip.
The majority of straight shank drill bits will be spiral bits although there are auger, Forstner and glass drill bits which have a smooth shank.
Straight shank bits come in a large variety of sizes both in diameter and in the overall length of the bit. Diameters are typically available in 1 mm up to 40 mm and the working length of the bits are between 10 mm and 530 mm on average.
The jobs that a straight shank drill bit is used for will be one where it is very important that the bit is properly centered and where a high degree of accuracy is required.
What Is A Hex Shank Drill Bit Best Used For?
A hex shank drill bit, as we have seen, has a greater amount of torque. While this is not the same as speed it does mean that the greater amount of force that can be directed through the drill bit means the job will get done faster.
The higher torque also allows the hex shank drill bit to be used on materials with higher resistance. This could include hard metals such as cast iron or even geological formations such as rock.
However the angle of the shank which allows greater torque also creates a slight wobble in the drill bit. This can affect the accuracy of the drilling which may not be centered.
These drill bits can be titanium nitride coated which reduces friction and extends the life of the bits. They are typically made from high speed steel which also reduces wear and increases durability.
The best use for hex shank drill bits therefore are for tough materials where precision is not paramount but durability and strength are needed.
Final Thoughts
Choosing the right drill bit for the job is important and this is not always just about the diameter and length. The type of shank also has a bearing on how well the drill bit performs.
We hope this guide to the straight shank drill bit and the hex shank drill bit has been informative and helpful.