Get the Most Accurate Positioning with Spot Drills
by Anthony Williams on August 28, 2019
Part of operating a milling machine is making sure your work is accurate. Modern milling machines allow end mill placement with pinpoint accuracy, making it possible to create incredibly intricate pieces with relative ease. When drilling into a workpiece, a walking bit can ruin all of your hard work. Instead of having to start an entire piece over because of a mechanical mistake, make sure your bit placement is accurate by starting with a spot drill. These simple little bits can help ensure that your drill bits provide the same accuracy you expect from your end mills.
The purpose of a spot drill is to get your workpiece reading for secondary drilling. Though these are drills of a sort, they are not used to create a full hole like a typical drill bit. Instead, spot drills are used to create a dimple in the workpiece to assist you in seating your drill bit perfectly. Spot drills have a short flute length and body to make them as rigid as possible. On rigid surfaces, traditional drill bits can easily be deflected off their target. This is because their length leads to a traditional twist bit being far too flexible.
Many machinists will try to get this effect using a cheaper center drill to start their holes instead of a spot drill. While center drills may look perfect for the job, preparing a piece for a lathe is different from preparing it to be drilled. There are two issues with this approach. First, the tip of a center drill is delicate, and can easily break while spotting, which can hold up your production. The second issue is that center drills typically have a 60° point angle. This is too narrow for most drill bit points and can actually lead to deflecting your bit.
The best tool for spotting is a true spot drill made from solid carbide. These bits are rigid and create spots with the correct angle to accept the tip of your drill bit without the worry of deflection. At Online Carbide, we make all of our spot drills here in the USA. We use the same quality carbide stock and grind equipment as industry leaders, but we offer our products at manufacturer direct pricing.
Our spot drills come in both 90° and 120° point angle options to accommodate the angle of your drill bit. You can find these spotting drills in sizes ranging from ?” to ½”. We also offer both our polished carbide bright finish and a titanium aluminum nitride (TiAlN) finish. Ordering a spot drill with our TiAlN can greatly extend the life of your bits by shielding them from heat.
If you want to avoid having a wandering drill bit ruin your hard work, take the precaution of spotting before you drill. If you need quality spot drills or end mills for your shop, you can save big and get amazing quality when you order from Online Carbide.