Tool Truck: Drill Bits

Drill Bits

Professional Tools. Professional Facts. You Ask The Questions, We Get The Answers.

Question:

My drill bits seem to get dull quickly. Is there a kind of drill bit that lasts longer than the rest? What is the best kind to buy?

Answer:

When it comes to drill bits, there are a lot of choices such as high-speed steel, black oxide, cobalt and titanium. While there are differences between these bits, all of them, regardless of the type, are generally well-suited for drilling metal.

Before you look for features and benefits of different bits, it’s important to first understand why drill bits get dull. What kills a drill bit is too much heat. Once a bit gets too hot, it loses its temper and becomes dull. Even if you sharpen it, it will dull again quickly, so you have to avoid building too much heat in your bits to make them last.

The heat buildup is caused by friction and the only way to reduce friction is to drill with the correct speed and pressure. If you spin a drill bit too fast, if you don’t put enough pressure on it or if you put too much pressure on it, you’re ultimately just building heat without cutting.

To refine your drilling technique, you should start with a good variable-speed drill with good trigger control. Start drilling at a slow speed with fairly heavy pressure. You should see metal chips and progress immediately to indicate proper cutting. Make minor adjustments in speed and pressure to get good results.

Different metals and different size drill bits will require different pressure and speed, so it takes a little getting used to.

Equally important as your technique is cutting oil. Simply put, cutting oil reduces friction and cools the bit and you should absolutely use it when drilling any type of metal.

As far as what to buy, more expensive bits such as cobalt or titanium-coated ones are designed to resist heat and friction, which will help them stay sharp longer. They will work better on harder metals like stainless steel, but keep in mind, you can ruin them just as quickly if you get them too hot. If you’re doing a lot with harder metals, you should consider bits that can handle the additional heat.

So, when it comes time to buy, consider the types of metals you work with most, look at your budget and make the best decision, keeping in mind that no matter what you buy, using the proper technique is what will make them last.

One final tip is the subject of a pilot hole. Many bits are available with a 135° split-point tip and these will generally start to cut quickly without a center punch or pilot hole, but if they don’t, this is a point where a lot of heat buildup will occur.

Drilling a pilot hole will not only ensure a perfect center but it will also allow your bits to cut immediately. A popular choice by technicians are double-ended bits, available in multiple small sizes and 10-packs. These are an economical choice that will save wear on your master set.

Jump on the tool truck. You will always be able to find the drill bits to fit your needs, always in stock, on your local tool truck. TS

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