When To Use Spot Drills, Stub Drills, And Jobber Drills

By Author: Geoffrey Less
Total Articles: 73
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While drilling holes is a relatively simple process when it comes to carpentry, moving from wood to metal poses some unique challenges. This is especially true when precision is required. In order to achieve the best results possible, you have to be sure to use the right tools when you are drilling into hard materials. Knowing when to use spot drills, stub drills, and jobber drills will help you create the perfect hole every time.

Spot Drills
Spot drills are the smallest type of drill bit in terms of cutting surface size. The cutting area of a spot drill is limited to the sharp point of the tool and they typically have small flutes that do not tend to extend far beyond the point. Instead of actually drilling holes, spot drills are used to “spot” holes by creating a dimple on the surface of a workpiece to mark the location of a hole.
The spotting process helps ensure that holes drilled with larger tools will ...
... be accurate. It is very easy for drill bits to deflect off of hard surfaces and miss their marks. As long as the tip of the spot drill is greater than the angle of the final bit, the longer bit should be able to seat itself easily.
Stub Drills
Stub drills are relatively short, but they do have the familiar twisted flutes that most people associate with drill bits. The shorter length of these drill bits helps to increase their rigidity, producing more accurate results. Depending on the material being drilled, you can sometimes use stub drills successfully without spotting.
Jobber Drills
When most people imagine a drill bit, they are picturing a Jobber drill. These twisted drill bits are the best tools for drilling deep holes in a workpiece. These drills have a long cutting area with spiral flutes for evacuating chips from the hole. While they are great for drilling deep holes, using jobber length drills in a milling machine can have complications.
The long length of Jobber drills make them the most likely candidate for missing their mark and drilling off center holes. Because these tools are so long, they naturally wobble when operating at high speeds. This is one of the reasons why spotting is so important when drilling into harder materials. With a correctly sized spot drill and a high quality jobber bit, you should be able to drill holes easily even when working with hard materials like steel and cast iron.
If you are looking for quality drill bits for your shop, solid carbide tools are always the best option. Carbide, a composite material made from metal and ceramic, is the perfect material for making tools that can handle high speeds and temperatures. Because the cutting power comes from the fatigue-resistant ceramic content, these tools will maintain their edges for long periods of time. Carbide cutting tools can also withstand higher temperatures than tools made from high speed steel alloys.
To find quality carbide drill bits for your shop, check out Online Carbide. They are an American manufacturer of solid carbide end mills and drill bits that they offer at manufacturer direct prices so shop owners can save on the high quality tools they need. You will find spot drills, stub drills, and jobber drills on their website in addition to a selection of high quality end mills. To see all of the tools they have to offer, just visit www.onlinecarbide.com.
For more information about Drill Mills and Drill Bit Manufacturers Please visit : Online Carbide.