Even the hardest bits will grow dull over time, even carbide-tipped masonry bits. This means that they will need to be sharpened when needed.
But, is it possible to sharpen a masonry drill bit? You can sharpen the masonry bit or concrete drill bits by grinding. This will help maintain their efficiency and avoid creating flaws or breaks in the material. But to sharpen the bits you will need the proper tools.
Tools: Grinder & Wheel
A grinder will help restore the masonry bits you use on concrete to be sharp and in like-new condition when you sharpen them the right way. This means that you can use the same bits repeatedly until they finally reach the point where they cannot be sharpened.
Bench Grinder
A bench grinder or a pedestal grinder is the standard machine tool for sharpening masonry bits. It has grinding wheels on both ends that rotate at high speeds and can sharpen most bits rather quickly. But you need the right type and grade grindstone. At my shop, I use the green silicon carbide grinding wheel to sharpen the carbide-tipped masonry drill bits.
You will also need other products and supplies such as safety goggles to protect your eyes and cold water to cool down the bits. Gloves are not recommended despite their protection because you might get them caught in the grinding wheel.
Drill Sharpener
While the bench grinder is a general-purpose tool, the drill grinder is a tool that is specifically designed for grinding drill bits. A drill sharpener usually has a diamond wheel and you can precisely set the cutting tip angle to grind.
The downside is that drill grinders are limited by the available collet sizes.
Bench Grinder or Drill Sharpener
Both types of grinders can do the job, but the bench grinder that is secured to the table or platform can be quite effective for grinding large diameter masonry bits.
For smaller diameter bits up to ¾-inch or 20mm, I recommend using a drill sharpener. The main reason is the safety that is inherent in a drill grinder.
A bench grinder offers better versatility and should be available in every shop. You can mount the silicon carbide grindstone on one end and the regular aluminum oxide wheel on another side. The regular wheel can grind softer steel such as angle irons and HSS drill bits. A good bench grinder can be quite useful in this regard.
Angle Grinder
For extra-large size SDS and SDS-plus masonry bits used in construction industry, you could use an angle grinder. Make sure that you secure the bit on a vise such that it will not move, so only your movements will apply in sharpening the masonry bits. It is one of the many uses of an angle grinder which is a very versatile power tool.
Silicon Carbide or Diamond Wheel
A diamond wheel is quite sharp and durable, allowing for many uses over its lifetime. The downside is that they are expensive and often cannot be mounted on a regular bench grinder.
If you can get a diamond wheel, do so. If not, you will need a silicon carbide (green color) grindstone or find a suitable replacement that is designed for masonry bits.
How to Sharpen a Masonry Drill Bit (By Hand)?
Sharpening masonry bits is a straightforward process, but you will need to take several steps in order to ensure that you do the job right. And most importantly, that you protect yourself in the process. While sharpening bits is easy when you do it the right way, you will need to protect yourself as one slip can cause considerable a painful injury.
Step-1: Preparation
If you have not set up your grinder, you will need to do so on your workbench. Clear away any unnecessary items and clean the bench by wiping it with a cloth. Anything that is flammable should be removed far away from the grinding area. Keep in mind that one spark landing on a flammable surface or liquid is enough to ignite it.
Now, secure your bench grinder to the surface. It will need to be close to the edge so you can easily stand in front and move your hands with the bit in place. You do not want to bump into the workbench or any object nearby, so be sure that you have secured the grinder properly and cleared away any obstructions.
Place your coolant or cool water near the grinder, preferably in a container large enough that the water will stay cool for a long time. This means avoiding using small cups along with large buckets. Something in-between is ideal if it can be set within easy reach. Now, place the bits you want to sharpen on the bench near the grinder and you are ready to begin.
Step-2: Inspect Each Bit
Start with the first bit and look at the tip, this is the area in which you will sharpen. The shank is the long stem that is at the top and the portion with spiral grooves is the body that connects the bit to the drill. Unless something has attached itself to the shank, you should never have to use the grinder on that part of the bit.
Hold the bit so you can clearly see the tip and rotate it to view all of it. Change the angle so you can see the tip fully and note any dullness, flaws, or other imperfections. These are the areas that you will sharpen. Now you are ready to sharpen the bits.
Step-3: Masonry Drill Bit Point Angle
The point angle of a masonry bit tip is 135 degrees. This is the included angle of the tungsten carbide tip. It may vary according to the manufacturer and the material that you are drilling holes into. I have seen drill bits with angles ranging from 118° to 135°.
The Irwin Joran masonry drill bits that I use have a tip angle of 135°. Below is a screenshot of the bit that I measured on the profile projector.
Hence the proper angle to hold on the grinder to sharpen masonry bits is 60 degrees to 67.5-degrees which will give you an included angle of 120° to 135°. This provides enough sharpness to ensure that any dullness will be removed while not removing too much of the cutting tip itself. Before turning on the grinder, you may want to practice a little in holding the bit so that you get a 60-degree angle when sharpening.
Step-4: Turn on the Grinder
Turn on the grinder and ensure that it is running smoothly. Place the bit in your hand so the tip is exposed as this will contact the grinding wheel. Place your forefinger on the grinder tool stop, this will help you guide the bit while keeping your fingers far enough away to be safe.
Step-5: Start Grinding the Cutting Edges
Be sure to hold the tip of the bit close to the grinding wheel and get set before pushing it in. Gently press the bit into the wheel and do so in pulses. This means pressing in for a few seconds and then pulling away slightly for a few seconds. This will help keep the bit from overheating in your hand. The goal is to sharpen the bit while keeping the temperature down, so you can hold it.
Step-6: Check the Sharpness
Once you have done a little sharpening, check the area which has been sharpened for any chips or areas of unevenness. This will indicate if the bit is either flawed or if you are holding it at the wrong angle.
Step-7: Grind the Clearance Angle
In addition to the edge, you will need to smooth out the heel of the masonry bit. This is the area just behind the cutting edges. This area should have clearance, so the drill can slide into the masonry easier and not drag or rub against the material. You’ll want to remove the material from the heel by setting the angle to the same 60 or 67.5 degrees but tilt the bit upwards and grind just behind the cutting edge.
As with the cutting edges, you’ll want to gently pulse the surface for a few seconds at a time to avoid overheating the tool bit. As you grind the relief rotate the bit slightly; this will let you gradually grind the surface evenly. Remember to dip the bit into the cool water every so often, especially if you are feeling it heating up in your fingers.
Step-8: Blunt the Edges
What? Yes, you heard me right.
The cutting edges of concrete drill bits are fairly blunt. This is to avoid the sharp tip getting chipped-off and breaking easily. When you use a masonry bit on a hammer drill, it not only rotates but also keeps hammering into the material to break into concrete, brick, mortar, stones, etc. If you keep the cutting edges tack sharp it will break the edges easily.
Use a buffing wheel or belt sander to slightly blunt the sharp cutting tips to increase the longevity of your tool bit.
Once you have completed sharpening to your satisfaction, you can move on to the next bit. Keep in mind that this will take some time, but it is time well spent to ensure that your masonry drill bits are sharp and ready to use.
Using Drill Sharpener
Drill sharpeners such as Drill Doctor are not only convenient but are also a safe way to sharpen drill bits. You can use a drill sharpener on a masonry bit or concrete drill bit, provided it has a diamond grinding wheel.
Here are the steps I follow on my cheaper Taiwan-made sharpener. The basic steps should be similar for most of the sharpeners, but I suggest you refer to the user manual and follow the normal operating procedure of the sharpener.
#1. Select the Correct Size Collet or Chuck
Measure the diameter of the drill bit and select the appropriate collet or chuck. For example, on DrillDoctor you can hold bits ranging from bits from 3/32″ to ¾″ in the ¾″ chuck.
#2. Set the Alignment and Depth
The diameter of your bit decides the web thickness. You need to consider this when you want to set the edge of the bit straight. Most drill bit sharpeners have an alignment port where you can align accurately and set the depth. Now it is time to clamp the drill bit in the chuck or collet.
#3. Set the Angle to 135°
Out of the box, these tools are set to 118° angle, which is the point angle of the general-purpose twist drill. For masonry drill bits, you want to change the angle to 135° or whatever was the existing angle.
#4. Sharpen the Carbide Tips
Insert the collet holder along with the drill bit into the drill sharpener and start grinding. Depending on the sharpener model, you may need to rotate the collet holder within the limits set on the tool.
The following image should give you a clear idea about the working of a drill sharpener. For your safety, please keep the covers closed while you do the sharpening.
Grind till the tungsten carbide tips are sharp. In case you see the remains of the broken tip, take out the collet holder, loosen the collet and push the drill bit further out. Repeat the grinding process.
#5. Grind Relief on the Heel
Once you are satisfied with the sharpness of the cutting edges, it is time to grind the clearance at the heel area.
Finally, make a very small radius on the cutting edges with a polishing stone and your masonry drill bit ready to cut through concrete.
Sharpening Masonry Bit for Steel
The regular HSS or even the tough cobalt or titanium drill bits can not penetrate hardened steel. Carbide bit works best in such cases. However, solid carbide drill bits are expensive.
You can use tungsten carbide-tipped masonry drill bits to drill hardened steel.
The method is exactly the same, except that you will not perform the last step. When drilling holes in hardened steel you want the cutting edges to be sharp. Hence, in this case, do not polish to make the radius on the sharp edges.
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