How to make a brad point bit from a twist bit?

28th February 2020


	How to make a brad point bit from a twist bit


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			In some woodworking and furniture making circles, grinding your own brad point bit is seen as a desirable skill that shows off your qualities as a craftsman. It may also become a necessity if looking for brad point drills in unusual sizes (e.g. 13/64″), as these may be difficult or impossible to find.

			Being able to create your own brad point bits allows you to control the length of the brad point in the centre of the bit, as well as the shape of the spurs. It also provides a way to guarantee that you will always have a brad point bit in the size that you need, even if you can’t find one to buy.

			There are two different methods that make this possible, one of which uses a rotary cutting tool and drill press, while the other uses a specially customised wheel on a bench grinder.

			The most important thing to remember for both methods is that the tip of the brad point bit has to be dead centre for the bit to drill with any accuracy. If it is not, the bit will drill a wider hole than its diameter, as it will spin off centre as soon as the brad point engages with the wood.

			Method 1
			This method involves using a drill press to rotate your twist bit while grinding it with a rotary cutting tool. The cutting tool should have a fibre reinforced cut-off wheel attachment (which is normally attached to a rotary cutting tool to cut through metal rather than grinding or polishing it). Using a drill press and clamping the rotary tool into place makes it easy to keep everything correctly aligned.

			Step 1 – Secure bit Secure your twist bit firmly in the chuck of your drill press.

			Step 2 – Set up rotary tool Your rotary tool needs to be fixed to your drill press table using a clamp. You will be using a cut-off wheel attachment, which will need to be able to spin freely for the duration of this task. Clamping your rotary tool into place, as well as using a drill press to secure your bit, guarantees accuracy.

			Check that your drill bit and rotary tool are correctly aligned with each other. The cut off wheel should be rigged to contact the bit just off centre, so that a brad point can be created.

			Step 3 – Grind brad point Activate your rotary tool and your drill press. Carefully lower the drill bit so that it makes contact with the cut off wheel, which will begin to carve out a brad point. Once you are happy with the length of your brad point, deactivate the drill press and the rotary tool.

			Your brad point does not have to be a specific length, as long as it sticks out beyond the cutting edge of the spurs. Longer brad points allow for drilling at an angle with more precision, but this is not often necessary.

			Step 4 – Shape spurs To correctly shape the spurs of your brad point bit, you will need to grind a slope behind the tip of each one. This is known as a “back rake”. Remove your bit from the drill press and colour in the top around the blunt brad point with a black marker. This will make it easier to see which part of the bit you have ground.

			Remove your rotary tool from the clamp and grind the edges behind each spur by hand so that they slope gently backwards, at an angle of around 10 to 20 degrees. Stand with the bit facing you, and grind the spur on the right hand side, starting from the lower edge and coming to a point at the top.

			Once you are done, the black mark you have made will have disappeared. Check your work by looking at the bit side on. The spur should have a smooth slope to it.

			Step 5 – Sharpen brad point You will now need to sharpen the brad point on your bit. If you choose to continue using your rotary cutting tool and drill press for this part of the process you will not be able to clamp your rotary cutting tool, as you will need to hold it at an angle. For a step by step guide, see: How to sharpen a brad point bit

			Method 2
			This method involves grinding the tip of your twist bit into a new shape using a bench grinder. For a step-by-step guide on customising a grinding wheel for this task, see: How to customise a grinding wheel to sharpen a brad point bit

			Step 1 – Choose drill bit Select the twist bit you would like to grind to a brad point. As more of your bit will be in contact with the grinding wheel at a time than it would be for the first method, high speed steel bits will work best for this process. This is because they are more resistant to heat than tool steel and less likely to lose temper through overheating.

			Step 2 – Set up a jig It’s important to be accurate when creating a brad point bit, as the brad itself must be perfectly centred. If it’s not, you will not be able to drill holes of an accurate size.

			Your twist bit will need to contact the grinding wheel slightly to one side of its centre. You will need to be able to remove the bit and replace it on the tool rest (the metal shelf in front of the wheel) on exactly the same line multiple times.

			To make sure this is possible, clamp a piece of wood with a straight edge onto the tool rest so that you can use it to rest your bit against. This will help you to relocate it in the same place each time you need to move it.

			Step 3 – Grind spurs Place the twist bit on the tool rest. Using the wooden jig as a guide, slowly push it towards the grinding wheel until it comes into contact with the angled groove. The wheel will begin to cut into the tip of the bit and form it into a brad point shape. The side of the wheel will shape the edge of the brad point.

			Remove the bit from the wheel and spin it 180 degrees on a regular basis to grind the opposite side. This will prevent your bit from overheating and keep your grind even.

			Your bit will take on a W shape.

			You can decide how long you would like the brad point in the centre to be. If you are planning on drilling angled holes, you may find a longer brad to be advantageous. Usually, though, you should stop grinding when the point is sticking out just beyond the end of the spurs.

			Step 4 – Complete shaping Your newly ground brad point bit is almost complete, but there will still be sections of web that will need to be ground down. If you follow the line of one of the flutes that starts from the point of either spur, you should see that there is extra material that still needs to be removed. This will be connected to the brad point in the middle of the bit.

			These should be carefully ground down on your grinding wheel so that there is a smooth, flowing line down from the tip of your spurs. You will find that removing this material also sharpens your brad point, which will be in contact with the outside of the wheel while you grind.

			As you grind, one of the spurs that you have created will be on the far side of the drill bit and obscured from view at times. Take extra care to make sure this does not come into contact with the grinder, or you will ruin its shape and have to start again.