Auger drilling bits have been around for a very long time and are still in use to this day. However, they have evolved in design over the years to make them more efficient.
Spade bits, on the other hand, have been around since 1968 when they were invented by the Irwins tool company. They have a flat spade or paddle-like design with sharp edges at the front to scoop out material.
To give you a better understanding of these two drill bits, we have done a head-to-head comparison, which is as follows.
Auger bits generally create cleaner holes with smoother sides and less splintering. As such, they are commonly used for general wood drilling in construction, woodworking in gardening, and many other areas.
However, spade bits create holes with rougher sides and are therefore used in areas that will be covered. For instance, when installing electrical conduits or water pipes through walls, this bit can be used because the holes will be covered by a better finishing.
2. Design: Flat vs. Spiral
The most notable difference between these two bits is their designs. Auger bits have a spiral design with a threaded tip at the front and two chisels at each end of the tip. These chisels are responsible for shaving the wood.
On the other hand, spade bits are flat. They have a simple design that is shaped like a spade or paddle with two sharp lips at each end and a sharp non-threaded guidance tip.
3. Ease of Use: Auger Bits Require Less Downward Pressure
Owing to its design, auger bits require less downward pressure when drilling, which makes them easier to use. The threaded tip bites and pulls the bit downwards and this creates a self-driving mechanism that can be very fast even with just the weight of the drill pushing down.
This is not the same case for spade bits. Their tips might be sharp but are not threaded and therefore, they don’t self-drive. As a result, you need to apply more downward force for quick digging. With just the weight of the drill, drilling can take a while.
The spiral design of auger bits makes them suitable for precision drilling. This means they can dig a hole that is the same width as the tool when cutting straight or at an angle.
On top of that, the threaded tip bites firmly into the wood to prevent shifting and this makes the cut highly precise.
With spade bits, you have better chances of customizing the shape and size of the drilled hole. This is because the tool can be easily angled at the beginning or even as you drill, which allows you to create a tapered hole or a smaller/larger hole than the width of the flat blade.
In this case, you should pick the one that fits your project’s requirements because none is better than the other. They are equally different.
5. Drilling Depth: Auger Bits are Better for Deep Drilling
Not only are auger bits very fast at drilling, but they can drill very deep. This made possible by their threaded tip, which self-drives the tool to very deep depths almost effortlessly.
Ideally, these bits can go up to 600mm deep while creating a very neat hole. In actual sense, the only limiting factor is the length of the tool.
However, since the bit has a lot of surface area in contact with the wood (at the front and sides) when making deep holes, it is recommended to do it at slower speeds to avoid overheating.
As for spade bits, they are not recommended for drilling at deep depths because you will have to apply a lot of downward pressure. On the bright side, they generate less heat even at fast speeds in deep depths.
6. Shaving Removal: Auger Bits Do a Better Job
Apart from drilling faster and deeper, another advantage that auger bits have is that they evacuate shavings very efficiently. This is due to their spiral section (flight), which directs shavings to the top, leaving the hole clear and unclogged.
Single-twist auger bits provide the most efficient evacuation, which enables you to drill deep holes without lifting the tool.
However, with spade bits, shavings usually pile up above the bit in the hole and at some point, you might not be able to see the paddle.
Therefore, this requires you to lift the bit and unclog the hole once it is filled up, which can be inconveniencing if you are drilling a deep hole or drilling multiple holes.
7. Cost: Spade Bits are More Affordable
Lastly, spade bits have the main advantage of being very affordable. Their simple flat design makes them cheaper than augers and this is quite logical because the material used to build them is less (they don’t have flights).
Note: It is worth pointing out that these two types of bits are not strong enough to be used on other materials such as metal. They are not versatile; stick only to wood drilling. Otherwise, look for a brad point bit.
To wrap it up, auger and spade bits are very different from each other in terms of design and use. Even though the former is better overall, the latter has some unique uses that still make it relevant to buy. This includes creating customized holes such as tapered ones.