Essential Tools: Drill Bits, Taps and Dies


Things break, it’s just a reality of the universe, and Murphy’s Law will dictate that things will probably break in the worst ways at the worst times. For people living in the midwest where they still insist on using salt on the roads, breaking bolts is a way of life. For the rest of us living in civilized states breaking bolts is more of an occasional experience. No matter the frequency though, it is never a fun time. Luckily for us these have been issues since the first car, and over the years tools and techniques have been developed to help us remove those broken bolts and get on with our life.

Drill Bits

Not all drill bits are made equally. There are drill bits for wood, concrete, soft metal, and hardened metal. Not only are there different use types, but even different designs, materials, and coatings within each category. Drill bits are actually a complicated subject, and one can get quite lost down a rabbit hole trying to figure out the best drill bit for the application. Luckily for those of us working on cars most of the material we will be drilling into is some sort of steel or maybe aluminium so we can narrow things down quite a bit. The two main drill bits you will be using are general purpose High Speed Steel (HSS) and Cobalt (HSCO) bits. HSS bits are your general purpose bit. They can be used in anything short of hardened or stainless steel and can even work in wood, and PVC, though specialized bits for those applications will work a little better. The problem with HSS bits is when it comes time to drill out that broken bolt, they are just not up to the task, That is when it is time to break out the Cobalt bits. Not to be confused with the Lowes house brand Kobalt, Cobalt drill bits contain up to 8% of the element Cobalt in the steel, causing them to be harder and stay sharper than their HSS brethren. These are the go to choice when trying to drill out broken bolts that tend to be made out of hardened steel. Caution needs to be taken with HSCO bits though, the same principles that make the drill bits harder also make them more brittle and easier to break if the wrong force is applied.

There are also coated drill bits that claim to offer longer service life and better cutting. Most of these coatings are designed for use in specific applications though and may not be the best for general service. Coatings can also make sharpening a bit either impossible or not worth it if the metal under the harness coating is too soft. A good set of drill bits will set you back a decent amount of money, but at the same time shouldn’t break the bank. No matter what brand, using the drill bit correctly will ensure long service life. Using cutting fluid on the bit, setting your drill to the correct speed, and applying the correct amount of straight on pressure will help make sure you don’t end up instantly dulling your bits.

Taps and Dies

If you are going to try and save money on your tools, do it elsewhere. Taps and Dies are the tools used to cut threads on parts. Taps are used to create threads in a hole, and dies used to create the threads of a bolt or stud. Generally you will probably find yourself using taps more than dies, since most of the time the bolt or stud is replaceable. Either way a good full set of taps and dies are important and not something to cheap out on. The last thing you want after spending all that time drilling out that broken bolt is for your tap to break in the hole. Taps are made of very brittle hardened steel so you are going to have a real fun time trying to drill out a broken tap.

Just like with drill bits, proper use of both taps and dies will ensure long life out of your tools. The use of cutting fluid is always recommended, and using the right amount of force. When cutting threads by hand it is best to use just enough force to cut into the metal, turn the tool in about 1-2 turns then back it off 1/2-1 turn. This should help make sure you cut clean threads and help prevent the tap from breaking. Just like with drill bits taking your time and having some patience will help. Making sure you drill the proper size hole and making sure the hole is straight will also help make sure your tap makes good threads and does not break. Most tap and die sets come with a chart stating what size hole or stud should be used for each bit.

The proper use of drill bits, taps, and dies is something that is hard to get across in text form. Best thing to do is find someone who knows and ask them to teach you. Second best thing to do it to go get yourself YouTube certified. One thing I would suggest is to go practice now. Figure out how to properly use these tools on scrap metal now so when you need to use them it is not intimidating. There are a ton more tools out there for when things go wrong like extractors, left hand drill bits, and thread chasers. We will cover all those in a future article. Next week though we are going to go over the thing you put all these new tools in, the humble tool box.


the authorm.overstreet
Matt Overstreet has spent the last 12 years working as an automotive technician, specializing in diagnostics and electrical. After many years in the repair field he has switched his focus to combine the world of cars with his other lifelong hobby of writing, bringing a unique take and expertise to the automotive journalism landscape. Growing up in Michigan Matt had a front row seat into the automotive world. While hot rodding and drag racing were the prevailing styles in the Midwest, thanks to a perfect storm of Fast and Furious, Initial D, and Gran Turismo Matts obsession quickly turned to Japanese cars, though he still has a soft spot for Domestic cars. He currently resides in Denver Colorado enjoying the spectacular mountain roads and nearby race tracks. You can catch him during the race season at Pikes Peak International Raceways honing his driving skills in their Time Attack Series

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