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Do you keep breaking drill bits when drilling holes? You are not alone. I also experience it, especially with small bits. But over time I have learned some tips and tricks that have helped me avoid breaking too many bits.
In this article, I share from my experience in woodworking the most likely reasons your drill bits break and 6 things you can do to stop it.
What causes drill bits to break and how to prevent it?
As I mentioned, you can’t entirely avoid breaking drill bits, especially the small ones. Sometimes it is the only way to know that the bit is worn and needs replacement.
But breaking drill bits every time is not okay. It definitely means you are doing something wrong and you need to correct it before you damage your workpiece or the drill. It is not even good for your pocket to always buy a set of new drill bits for every project.
The following are the 7 most common reasons why drill bits break too easily and some corrective measures you can take to remedy the problems.
1. Applying excessive force when drilling
If you push the drill bit too hard into the workpiece, you will exert too much force on it. The excessive force can be unbearable for small drill bits especially when you take into account the rotation force of the drill.
The simple solution to this problem is to avoid applying a lot of pressure on the drill. Remember your work is to guide the drill so that it can make a nice hole for you. I broke so many small drill bits before I learned this simple hack.
If you push the drill bit too hard, you not only risk breaking it but also damaging the tool and the workpiece. As you probably know, a large bit can take more pressure before breaking, which means the drill will bear the extra pressure. As a result, the motor may overheat or the chuck shatter before the drill bit crumbles.
2. Poor quality drill bit
Cheap quality drill bits often fail when you put them to the real test. The deeper you drill the harder it is for the bit and a bad quality bit will fail. As you drill deeper into the workpiece, it becomes harder for the bit to cut through the grain. If you are using a bad quality bit, it will shear apart and break.
The best solution is to use good quality drill bits especially if you are drilling holes into a hard material or if you want to drill deep holes. In my experience, I have found bits made from stainless steel to be more reliable.
3. Not maintaining the same angle when drilling
Even the best quality drill bit will break if you don’t maintain the same angle when drilling. This is a mistake most people do especially when trying to make a pocket hole without a jig.
When you change the inclination of the drill bit, you will not only widen the hole but also subject the bit to forces on the side that will cause it to bend. And if the bit is made of brittle material such as cobalt it will break when you exert too much pressure on the side.
Therefore, you should always maintain the angle you start off with when drilling a hole with a drill bit. This is not difficult when drilling perpendicularly but can be tricky when drilling a hole at an angle. You can use a drill guide to help you drill angled holes more accurately and consistently. I like to use the Kreg pocket hole jig to drill angled holes into wood and it makes pocket hole joinery so easy to do.
4. Drilling too slow or too fast
You will likely break or damage the drill bit if the feed rate is too high or too slow. Drilling too fast or too slow can cause the bit to overheat and become brittle, increasing the chances of it breaking or chipping off. You should run the drill at a moderate speed, especially when drilling dense materials.
Another mistake you should not do is to force the drill bit too hard into the material. Most of the time, all you need for those smaller bits is the weight of the drill. Any additional force may cause the bit to break.
4. Not cleaning the hole frequently
Do you clear the chips from the hole or do you just drill all the way through? If you don’t remove debris that is the likely reason why your drill bits break. The dust increases friction
The best practice is to drill a short depth at a time and back out to allow the chips to clear out of the hole. The chips carry away heat and prevent the drill bit from overheating. This style of drilling small depths and clearing the chips is called peck drilling.
If you don’t clear away the debris frequently enough, heat will build up in the hole and will burn the wood as well as cause the drill bit to overheat. When a drill bit overheats, it may harden and become brittle, thus increasing the chances of breaking.
The size of the chips formed in the hole also matters when drilling into different materials. If the chips are too small, they will be compact inside the hole and cause overheating even before you clear them out.
This is quite common when drilling metals, especially stainless steel and other hard metals. Most machinists would attest. The best way to avoid it is to drill at low RPM and apply slightly more pressure if you are using a bigger drill bit. It will help create proper size chips.
5. Using a worn out drill bit
A drill bit with a dull tip does not easily cut through the material. It experiences resistance that may cause it to spin at a slower rate. As a result, the bit may overheat due to increased resistance and may eventually break. Not to mention the extra force the drill puts out on the worn bit may cause it to break prematurely.
The best way to avoid worn drill bits is to inspect them every time before use. Some signs that tell you a drill bit is worn and needs replacement include a blunt tip, chipped-off edges, burning marks, or a bent shank.
6. Using the wrong drill bit
Most drill bits have specific materials for which they are built. There are bits for wood, metal, glass, etc. If you use a drill bit on the wrong material, you will damage it or even break it.
A common mistake most of us do is to use drill bits for wood on metal or vice versa and complain when they break. You should always use the correct type of drill bit for the material you are working on. Most of the time the packaging for the bits will be labeled accordingly for easy identification.
That being said, there are some general-purpose drill bits that you can use on a variety of materials. For instance, a high speed steel (HSS) bit can work on wood, plastic, and soft metal but will break if you use it on hard materials such as steel.
The table below is a summary of common types of drill bits for hand drills, their composition, and where to use them.
Common types of drill bits
|Carbon steel with chrome and vanadium
|Best for soft metal, soft wood, and plastic.
|Steel alloy with Titanium Nitride coating
|Best for soft metal and hardwood
|Steel alloy with 5-8% cobalt
|Best for hardened metals such as bronze, stainless steel
7. Blunt drill bit tip
Another thing to consider is how sharp the tip of the bit is. It is often given in angles. The most common drill bits are either 118 degrees or 135 degrees sharp. The smaller the angle the sharper the tip. There are also bits with sharper tips such as the brad nail drill bits and others with a pilot hole screw at the tip.
Drill bits with sharp tips skid less when cutting without a pilot hole and cut faster. Unfortunately, they are more likely to break because the sharp tips are fragile.
Generally, 118 bits are good for soft materials whereas 135 drill bits work well with harder materials.
Well, these are some of the most common reasons why drill bits break and simple things you can do to avoid them.
But because no amount of care will prevent small drill bits from breaking entirely, you should always have a set of replacement bits on hand so that when that time comes, you will not waste your productive time looking for replacement bits.
Also, use cutting oil when drilling into the metal workpiece to cool and lubricate the drill bit. Just squirt the oil into the hole as you drill to absorb the heat. Do not use water to cool the bit because water is not a good lubricant and can cause the metal to rust. Moreover, water has a low boiling point, meaning it will evaporate easily and not cool the bit as effectively as cutting lube.
What other tricks and tips do you use to make your small drill bits last longer? Tell us in the comment section.