Forstner Bits Do’s and Don’ts

Forstner bits aren’t your normal type of drill bit. There’s some things that they do that others don’t. They can cut holes that are smooth bottomed as well as the sides.

They come in handy for cutting mortises to make it easier to remove material with a mortise chisel. There’s some instances that you’ll want to use a forstner bit over a hole saw or even a spade bit.

I also go over how to properly use them and when not to use them. Plus some guidance on whether you should buy a whole set or individually.


Why Use A Forstner Bit Over A Spade?

Before we understand why a forstner bit should be used over a spade bit, we first need to know what it does. The forstner bit is designed to drill holes that have smooth walls. The bit also creates a nice smooth bottom for things such as dowels.

If your wood project calls for a lot of dowels the forstner bit will be more precise not only in depth but diameter. Sure a spade bit can drill a hole but the tear out could keep the dowels from fitting into the holes snug.

Forstner bits work very well with drill presses for a few reasons. The drill press has a depth stop to keep your bit from going deeper than desired. It also has a speed control which is needed when using these types of drill bits. The forstner bit is designed to be used at slower speeds.

Drill presses also guarantee straight ninety degree holes or any other angled hole that you may need. An example of where to use this type of bit is with mortise and tenon joinery.

The way that this works is when cutting mortises, you overlap your holes to remove most of the material. Then removing the rest of the wood from the mortise with a mortise chisel becomes much easier.

The point of a spade bit has more of a chance to walk on you than a forstner bit does. The design of the bit with its smooth sides keeps this from happening.

Spade bits are fine if drilling through two by fours and floor joists for wiring and plumbing. 

Using Forstner Bits Instead Of Hole Saws

Hole saws are great for drilling holes through thin material in a hurry. However holes saws do have limitations. They don’t work all that great if a hole needs to be bored through hardwood. They tend to burn and dull out.

Forsnter bits on the other hand do a great job of cutting holes through soft and hardwoods. It may take a little more time due to the slow speed drilling. When done the hole will be more precise and much smoother than what you’ll get with a hole saw. 

Hole saws also can’t drill as deep as a forstner bit either. The hole saw will only drill as deep as the height of the bit will allow. The forstner bit on the other hand can drill deeper holes. 

When hole saws get dull you either have to change it out with a new one or sharpen it. The process of sharpening a hole saw is quite tedious.

When a forstner bit gets dull the process of sharpening it is much like the way you would sharpen a chisel.

Forstner Bit In A Hand Held Drill?

Safely use forstner bits in a hand drill

Using forstner bits with a hand power drill, is it possible? The quick answer is yes but there are some things to keep in mind when doing so. As mentioned before, forstner bits work better when drilling at slower speeds.

The only way to ensure that you can get to a slower speed on a hand drill is to make sure that it’s a variable speed hand drill. You won’t be able to get by with any other type. 

Also with a hand drill it’s harder to drill exactly straight down into wood. Forstner bits when used with a hand held drill also have a tendency to walk or drift along the workpiece which will result in a nasty scar or won’t be where you need the hole to be. 

There are ways to get around this though. What you can do is take a piece of scrap plywood, drill your hole with the size of the forstner bit you need. After the hole has been bored, clamp the plywood over the work piece. What this does is creates a guide for the bit to ensure that it doesn’t walk on you.

The best type of forstner bit to use with a hand drill are the ones that have a wavy pattern along the cutting edge. This type enters the wood cleanly which in turn reduces the chances of walking and tearout significantly.

The design of forstner bits are different from your ordinary style drill bits. They don’t have flutes to remove material like an auger does as you’re drilling into a workpiece. 

The correct way to drill with a forstner bit is to lift it up from time to time so that the wood chips come out the hole. If you don’t do this important step you’ll end up over heating the bit which results in dulling. 

Forstner Bit And Router?

Is it safe to put a Forstner drill bit in a router? No it’s not a good idea for one good reason. The router, no matter what type, is a high speed woodworking tool. You can’t adjust the speed to get it slow enough for a forstner bit to work. 

Forstner bits tend to blow apart when used at high speeds which could potentially injure you.

What you should do instead if at all possible is use a drill press. If that’s not an option then the next best thing is to use a variable speed hand drill. But use this option with care to make sure that you don’t damage the forstner bit. Slow and steady wins the game.

Forstner Bits Burning My Wood?

The Forstner bit keeps heating up so how to avoid burning the wood? A few things can cause this. The easiest thing is that maybe the bit has become dull. You can either sharpen it which I would learn how to do. The other option is to just replace it. 

The other thing that could be causing the burning is maybe your’e drilling a little to fast. Try slowing down a bit and see if that solves the problem.

Forstner Bits: Buy Cheap or Buy Quality?

If you’re looking for a cheap/decent forstner bit set, there’s a few things to consider. First off if it’s cheap the cutting edge won’t last as long as one that’s made from quality material such as the carbide forstner bits. 

The carbide type works very well on MDF and hardwoods where high speed steel (HSS) would struggle a little bit.

It doesn’t mean that they won’t work. You’ll just find yourself having to sharpen them more often if you use them constantly.

My forstner bit recommendation, if you don’t have the money to spend on quality bits, is to only buy the certain sizes that you need right now. 

If you happen to be a woodworker that doesn’t use forstner bits all that often then buy the cheaper ones. No point in spending money on something that doesn’t get used very much.


This guy explains how to use a forstner bit in a hand drill