When referring to handheld drills or drilling units, run-out (or runout) occurs when the drill bit does not circulate around its own axle in an absolute straight line (picture 1). It is
very difficult to get rid of all run-out, but it is important to minimize it as the end quality of the hole is ultimately affected. In other words – the final hole will not be 100% round if there is too much run-out.
There are many factors affecting the amount of run-out:
- The drill bit
- The chuck or collet
- The operator
- The tool
How to ensure run-out is reduced
When tightening a tool chuck, use all 3 positions to tighten with an even torque, using the chuck key. This will create equal pressure from all three jaws in the chuck holding the drill bit and reduce run-out (picture 2). Check the inside of the chuck jaws for damage or wear. If the jaws are worn, this could create excessive run out. A chuck is a consumable and should be changed from time to time, depending on usage.
When run-out occurs…
It is helpful to know the statistics regarding reasons for run-out, so that you can assess and anticipate why this may be happening. Most likely – 90% of the time – the drill bit in use is damaged or corrupt. 9% of the time run-out is experienced, the tool’s chuck teeth are damaged or worn out. Only 1% of the time is the actual tool damaged or not assembled correctly (picture 3).