A lot of the holes I drill tend to be into brick, masonry, or concrete, and I find that I am constantly having to change drill bits as they become dull and lose their edge.
For me this is a problem as masonry bits are not cheap so I looked at the best ways to re-sharpen them and save some money here’s what I found:
To sharpen a masonry drill bit you need a bench grinder, cold water, safety goggles, hold the drill bit in both hands horizontally on the machine stop keep it at 60 degrees to the grinding wheel. Press the drill against the grinding wheel, twist the drill clockwise, and drop the shank of the drill pushing the tip up the grinding wheel, repeat on the other side, keep the cutting edges symmetrical.
By sharpening my own masonry drill bits I have saved my self lots of time and money now that I don’t have to go to the store and buy new ones every time they become blunt or dull.
By practicing these techniques you can save time and money too but there are even easier ways to sharpen a masonry drill bit which I’ll show you at the end of this post, let’s take a look:
Setting up the grinder and your workbench
Find a space on your workbench that allows access to stand in front with plenty of space to move your arms and elbows, clear any tools or junk away. Move anything flammable away from the grinding area.
Set a small 8” or 10” bench grinder securely to your work surface, place it close enough to the edge that you can stand in front of it so that you can easily move your hands around without bumping the workbench or anything else.
The bench grinder should be bolted or clamped firmly so that it won’t move.
Make sure you have some clean cold water nearby, some bench grinders have a small container for quenching water, however, I prefer to use an old plastic ice cream tub as they are larger and the water will stay cooler for longer.
Parts of a Drill bit
There are several different parts to a drill bit the “Tip” this end cuts the hole and is made up of the cutting lip, chisel edge, and relief heel.
These are the areas that cut the hole when drilling and become blunt or dull over time and will need resharpening.
The length of the drill is called the shank these can be straight for use in most hand drills or have a morse taper for use in pillar drills.
Along the length of the drill, there are grooves called the flutes that allow swarf and debris to be removed whilst the drill turns. The outer surface along the flute length is called the land and this runs all the way to the cutting lip.
The flutes are cut two thirds the length of the drill on a straight shank to allow the chuck to grip the shank fully.
Setting the drill bit correctly
Hold the drill bit in both hands using the tips of your thumb and forefingers this allows you to move the drill in any direction.
The grip should be right hand about 1” from the drill tip and left hand on the drill shank, find a position that you feel is comfortable. This will come with practice.
Grind the drill bit cutting edge
Caution: You will be putting your hands near to a high-speed wheel so take care, put on some protective clothing, I wear safety glasses and use ear protection, as grinding wheels can send out sparks and be very loud. DO NOT WEAR GLOVES as they can get trapped in the wheel
Always remember safety first!
Turn on the grinder and holding the drill bit firmly in between your fingers, place the forefinger of your right hand on the grinder’s tool stop. Hold the drill bit so that the tip is within 1mm of the grinding wheel.
Use the existing brill bit cutting edge as a guide to set the angle of the drill, you need to set this to 60 degrees or as close as you can.
Touch the masonry drill bit against the grinding wheel, and apply some pressure to clean up the face, only hold the drill against the grinding wheel for a short period, this will help to stop the drill from getting too hot.
Remove the drill bit and check the face is ground clean and evenly, look for any chips or uneven areas. You are aiming for a clean cutting lip.
You can use an angle gauge to check the drill bit cutting face it should be at 118 degrees or a quick tip is to put two hex nuts together and hold the drill in between them.
You can use the angle between the hex nuts because they have 6 sides and are set at 60 degrees (360 / 6 = 60)
Repeat this process on the other cutting face by turning the drill over in your hands.
Aim to have both cutting edges symmetrical and the same length,
Grind the drill in short bursts and use the water to cool the drill bit down, be careful as a small piece of metal can become hot very quickly when grinding I tend to dip the drill bit into cold water after each grinding.
Grind the drill bit clearance face
With the cutting face ground, the masonry drill bit will need to have clearance behind the cutting edge, this area is called the heel, grinding this back, stops the drill from dragging or rubbing.
Again hold the drill in between your thumb and forefingers and rest your finger on the tool stop.
This time with the drill set at 60 degrees to the grinding wheel, offer the drill to the grinding wheel and an incline so that the surface behind the freshly ground cutting edge touch’s the grinding wheel first.
The goal is to remove material from behind the cutting edge so that only the cutting edge will contact the surface when you are drilling holes.
There are two ways to do this and which one you use will depend on your preference and the type of drill bit you are sharpening.
The first method is quick easy but not 100% correct, keep the drill stable in your hands and apply pressure so that the grinding wheel removes material in one area,
Check the cut is even and parallel to the cutting face, this will give clearance and can be used on most TCT (Tungsten Carbide Tipped) drill bits which are commonly used as masonry drills
The second method requires a little more practice and can be used on most standard twist drills as well as for resharpening masonry drill bits.
Again holding the drill bit in both hands set the drill against the grinding wheel as before parallel with the cutting edge.
With a slight incline on the drill bit, push the drill forward, up and twist it clockwise using your fingers, this all happens in one motion, this gives a better grind and will make the clearance more even across the drill bit.
This action will take practice so try it on a few old drills at first. Aim to have equal lengths on both cutting and clearance surfaces.
Use a sharpening tool
As I said at the beginning of this post you can resharpen masonry drills and save yourself time and money, if you want to save even more time or don’t want to learn the skills above another option is to use a drill sharpener.
One of the best makes of drill sharpener on the market is Drill doctor, they have several different machines to suit your wallet and your needs.
I recommend the Drill Doctor XP as it will sharpen most drills including masonry up to ½” dia, the Drill Doctor XP is easy to use by following the instructions, it comes with a 3-year warranty, and you can buy spares and replacements easily and is a reasonable price.
On Larger drill bits the Drill doctor can take a few passes, so be patient and take your time.
Drill doctor makes sharpening drills really easy, check out the latest prices here and put a new lease of life into your old drills.