how to sharpen metal drill bits

As an electrician and a home handyman, drill bits are a part of my everyday electrical tool kit. Most people at one time or another have used some sort of drill bit be it a wood drill, masonry drill or a metal drill bit. The problem arises when these drill bits go dull.

Today I am going to show you how you can sharpen drill bits using everyday items that you can find in your tool shed. As well as the correct procedure to sharpen each drill bit so that they are razor sharp to make your job easy.

Now before we start I just want to say that it is important to use eye protection like safety glasses or mono goggles. As we will be grinding away metal at high speeds it is important to be safe. Make sure you know how to quickly turn off any machinery if something goes wrong. Now let’s get into sharpening your tools.

How to sharpen drill bits using a bench grinder

I like to sharpen all of my drill bits using a bench grinder. This process can give you a very sharp edge and it is one of the most popular methods around.

Start by looking at the tip of your drill bit, to work out why it won’t cut. There are a few possible reasons such as:

  • Is the drill bit tip broken
  • Does the cutting edge look blunt
  • Are there chips in the cutting edge
  • Do you need to drill a pilot hole first?

Any of these reasons will cause a drill bit to go slow in the cutting of metal or wood. The point angle and point edge will do all of the cutting.

Drill bit point angle

Place the drill bit close to the grinding wheel at around a 45 deg angle and start to grind down the cutting angle. It’s important to have the trailing edge of the cutting angle lower than the front. This way you won’t have any high spots.

As you are grinding away, make sure to continually cool your drill bit using a small container of water. Every few seconds dip the tip of the drill bit into the water to cool it down. Excessive heat will decrease the hardness of the drill bit and we don’t want that.

Make sure that point angle is exactly the same on each side of the drill bit otherwise you will have excessive vibrations when drilling which may cause the bit to jam or break. The hole will also become uneven.

Keep looking at the face or tip of the drill to see how it looks. This is all done by eye and it may take a few goes to get it perfect. Often all that is needed is a new cutting edge which should only take a few seconds of grinding.

For a real test clamp down a piece of metal or wood and use a battery drill to make a hole. Each chip or swarf should come out even in the drill flutes. If only one side is cutting you will need some more sharpening of the drill bit.
If the bit doesn’t cut very well, you may have ground down too heavily on the cutting edge, versus on the heel of the bit. Try regrinding at a steeper angle, so that the heel or trailing edge of the cutting tip is formed behind the cutting edge. We don’t want any high spots.

You can also use a hand grinder with a grinding disc. Don’t use a cutting disc as there is not enough thickness in the disc to sharpen the drill bit safely.

It is best to clamp the hand grinder into a bench vise and then use the same process to put a nice cutting edge on the drill bit.

How to sharpen drill bits with a Dremel

how to sharpen drill bits with a dremel

Dremels are a tool every handyman should have in their toolbox. Not only can they drill and grind but they are great for sharpening small drill bits. Remember to always wear hearing and eye protection when working with your Dremel.

I like to use the circular barrel sandpaper tooltip. These are often included wit in the spare parts kit in various grades. Use something finer like a 200 grit sandpaper with the highest speed setting.

If you don’t have the barrel fitting you can also use a flat disk or a round stone to sharpen your drill bit. I tend to use a Dremel for 1/2 inch or lower drill bits otherwise it will take too long to sharpen them.

Use a bench vise to clamp down your drill bit tightly. Then use a Dremel to slowly grind away the tip of the drill bit leading edge until you have a nice sharp cutting edge. Do this on both sides of the flutes. Remember to keep your angles identical on both sides.

how to sharpen drill bits

Drill a test hole to make sure your drill bit is cutting nice and true. Any wobbling, squealing or excessive heat generation may indicate an incorrect sharpening edge.

How to sharpen a drill bit with a file.

The problem with sharpening a drill bit with a regular file is both metals have been hardened. This means we must use a diamond file to put a cutting edge onto a drill bit.

Diamond files use thousands of miniature diamonds which have been glued on to a base. For more expensive files the manufacturers use a process of electroplating diamond on to a steel file blank using nickel.

As diamonds are one of the hardest materials on this earth they are great to use as a cutting agent. The benefit of using a diamond file is they cut in both directions, unlike a regular file that only cuts on the push stroke.

The process to sharpen a drill bit with a file is the same as using a bench grinder or Dremel. I like to start from the trailing edge and work my way forward just taking a very small amount of material away.

This way as I reach the cutting edge all of my angles should be the same. Just take your time and you will end up with a very sharp cutting drill bit.

How to sharpen left-handed drill bits

The only difference between a left-handed drill bit and a right-handed jobber drill bit is the twist on the shaft. The cutting edge is designed to cut in reverse.

The process is the same as putting on a sharp cutting angle edge and then grinding away the lip relief angle. Everything will be opposite to sharpening a standard jobber drill bit.

You may wonder why there are left-handed drill bits? Well, they are designed to extract broken screws and bolts without having them twist in any further.

Sometimes when you are using a left-handed drill bit the bolt or screw will come out as the drill is cutting into it due to the anti-clockwise forces.

In fact, I had to use a set when I had a broken bolt in a Sea-Doo jetski cooling water ride plate. Without the left-handed drill bit, there could have been a possibility of the screw getting twisted in further and being lost into the cooling system.

Drill Point Angle Chart for Different Metals.

Harder materials such as stainless steel require a larger point angle, and softer materials require a sharper angle.

Sharpen Drill bit point angle, lip angle, helix angle chart
Metals MaterialPoint angleHelix angleLip relief or
clearance angle
Aluminum90 to 135 deg32 to 4812 to 26 deg
Brass and Bronze90 to 118 deg0 to 2012 to 26 deg
Cast iron90 to 118 deg24 to 327 to 20 deg
Mild steel118 to 135 deg24 to 327 to 24 deg
Stainless steel118 to 135 deg24 to 327 to 24 deg
Plastics and Wood60 to 90 deg0 to 2012 to 26 deg

How to keep your drill bits sharper for longer.

When cutting into metal always use a cutting fluid for lubrication and to keep the drill bit cool. Overheating the drill tip is a sure way to lose its hardness and cause the drill to become blunt and dull.

If you don’t have any cutting fluid you can use small drops of engine oil, WD40 spray, CRC, or even saliva. If you are out in the middle of nowhere just take your time drilling and stop every few seconds to allow the drill bit to cool down. This way your tip will stay sharper longer.

I have seen inexperienced users create so much heat that the drill bit was glowing red hot and quickly failed.

When I put them away a light spray of WD40 or any other lubrication oil will keep them from rusting over time. Lanox is a favorite of mine, I use it everywhere.

How to Sharpen Drill Bits with a drill doctor 750x.

how to sharpen drill bits with a drill doctor

The professional way of sharpening your metal drill bits is to use a machine called a Drill Doctor. Now, these have been around for a while and there is a whole range of different models. They can sharpen sizes from 3/32-inch to 3/4-inch, which will cover most handyman sizes.

Each has the basic features to sharpen your drill bits but others have spare cutting wheels, custom point angles, split bits, and more advanced features.

I would say for those that want or need a perfectly sharpened drill bit then this is the way to go. For those that are a DIY that has a blunt drill bit, well I would say save your money and use a bench grinder or a Dremel.

The only side effect I can see with using the drill doctor is the time required to set up the machine. By the time I get it out, plug it in, set up the drill in the jig tool, make a fine adjustment, and start to grind it, I would have already been finished on the bench grinder.

For machine shops and metal workers that are continuously drilling into metal, I would say the Drill Doctor is a must. It is a very clever little machine.

Conclusion

Always use the correct drill bit and speed for the job. Never use a masonry drill bit to try and cut into metal or wood. It can cause excessive heat and the drill could fail.

I never like to trust cheap drill bits from China that you find on eBay and supermarket shelves. You will find that they haven’t been heat-treated properly and tend to use cheaper materials to make the drill point. Stick with the hardware store bits.

If you are cutting into glass, tile, or ceramic objects, always use a diamond tip drill bit on a slow setting with plenty of cooling fluid.

When sharpening drill bits, take it slowly and stick with the correct point angles for the material you are cutting into. A point angle of around 120 deg to 135 deg is the most common angle which will cut into most materials.

If you have a spare drill bit you can use it as a template to match up with the one you are sharpening.

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