Computer numerical controlled milling machines are capable of doing a lot of jobs in a fraction of the time it would take to perform by hand. Despite this fact, the jobs that a milling machine can perform are limited by the cutting tools being employed. While end mills can perform a lot of milling operations, traditional twist drill bits are still the preferred tools for creating holes in a workpiece. Sadly the high speeds that milling machines operate at can cause some drill bits to miss their targets. That is why it is important to know how and when to spot drill so you can get clean and accurate results. Computer numerical controlled milling machines are capable of doing a lot of jobs in a fraction of the time it would take to perform by hand. Despite this fact, the jobs that a milling machine can perform are limited by the cutting tools being employed. While end mills can perform a lot of milling operations, traditional twist drill bits are still the preferred tools for creating holes in a workpiece. Sadly the high speeds that milling machines operate at can cause some drill bits to miss their targets. That is why it is important to know how and when to spot drill so you can get clean and accurate results.
Drill bits are designed to produce holes in a workpiece, making them invaluable tools in many manufacturing environments. The biggest issue with drill bits is that they are extremely long relative to their width. This can cause them to oscillate when they reach high speeds. While you might not think of drill bits as flexible, they oscillate enough for the point of the bit to swing away from the central axis of the bit’s rotation.
The issue of stability can make accuracy a huge problem. When making contact with hard surfaces, such as metals, oscillating points on long twist drill bits can walk off their mark and cause the hole to be drilled in the wrong location. When accurate is crucial, these kinds of mistakes can ruin the workpiece.
One of the best ways to improve the accuracy of your holes is to use a shorter drill bit. If you do not need the full length of a jobber style drill bit, stub length drill bits are a great alternative. These shorter drill bits tend to be far more stable at high speeds. However that shorter length is a limitation when it comes to working with these tools. If you need to use a longer drill bit, then you might want to consider using a spot drill first.
Spot Drills are extremely short drill bits that are essentially just a fluted cutting point. Instead of being designed to drill holes, these tools are meant to create a small, sone shaped dimple on the surface of your workpiece to mark the location of the holes that will be drilled with your longer twist bit. As long as the point angle of your long bit is equal to or less than the point angle of your spot drill, the bit should easily seat itself in the dimple instead of walking off its target. This extra step takes a little more time, but is necessary if you are manufacturing components with tight tolerances.
Another way to increase the accuracy of your holes is to use solid carbide drill bits. Carbide is a composite material made up of ceramic powder cemented together with metal. The ceramic nature of carbide tools makes them more rigid than their metal counterparts. This means that carbide drill bits can often be used without spot drilling. In addition to being more accurate, carbide drill bits will also stay sharp longer and offer a superior tool life to metallic tools. This is because the ceramic granules that make up the cutting edges are resistant to heat fatigue and nearly twice as hard as steel.
If you are looking for high quality carbide drill bits for your shop, Online Carbide is an American manufacturer specializing in precision ground solid carbide end mills and drill bits. Their inventory includes solid carbide jobber drills, stub drills, spot drills, and center drills. You can see all of the tools they have for sale when you visit www.onlinecarbide.com.
