Spotting drill vs. center drill - what's the difference?

Before drilling a hole, it’s common to use a spotting drill or center drill to ensure accuracy for the drill. Spotting drills and center drills may look similar at a glance, but they are actually intended for two different purposes. Let’s take a look at the uses for each.

When should you use a spotting drill?

Drilling a very precise hole can be challenging. Irregularities in the material, flex in the drill, and other factors can contribute to imprecise results.

A spotting drill is used to create a small dimple or divot in your workpiece prior to drilling. A traditional drill can flex, causing it to “walk” or wander off of the desired location and decrease accuracy. The dimple created by the spotting drill helps locate the center and can prevent this problem.

Spotting drills are shorter and stiffer, reducing flex, and have few, if any flutes. Spotting drills also have a point angle that’s slightly larger than the point angle on your drill, so that the center of the drill is the first portion to contact the workpiece. If the reverse is true (the spotting drill point angle is smaller) damage to your drill could result.

Spotting drills are offered from popular brands like Micro 100 and YG1

When should you use a center drill?

The primary function of a center drill is drilling a hole to be used as a lathe center. Center drills have a pilot section, acting as an oil reservoir. All Industrial Tool Supply offers center drills from brands like Harvey Tool and Fullerton Tool. 

A secondary purpose is using a center drill as a substitute or alternative to a spotting drill in some circumstances. Even though it may not be the intended purpose of the tool, it can work for some applications.

Can a spotting drill substitute for a center drill, or vice-versa?

Sometimes. While it’s ideal to use the correct tool whenever possible, machinists will sometimes substitute a center drill for the purpose of spotting, instead of using a spotting drill - perhaps because center drills are sometimes less expensive than spotting drills.

Downsides of making this substitution: center drill pilot tips can be delicate, and subject to breaking at a much higher frequency than spotting drills. Center drills commonly have a point angle of 60 degrees - as mentioned above, this may or may not be ideal, depending on the drill angle. If the point angle is less than desirable, the drill could deflect, reducing accuracy.

Finally, center drills can also generate more heat during machining.

All Industrial Tool Supply offers a wide selection of both spotting drills and center drills, so you can use one, or both to get the desired results based on your project, resources, and the material. Call our team of experts to discuss the pros and cons and we’ll help you choose the right one.