Drill chucks are used to hold drill bits for drilling operations of all kinds. Drill chucks are used on hand drills as well as on lathes and milling machines. Keyless drills eliminate the need for a chuck key to tighten and loosen the jaws to remove or place a drill bit and have both good and bad aspects over traditional keyed chucks.
Ease of Use
Keyless chucks eliminate the need for a chuck key to open and close the jaws of the chuck. You simply hand tighten the chuck after inserting the drill bit or cutting tool into the space between the three jaws. Machinists and others who use drill chucks have a tendency to lose chuck keys, so this prevents that from happening; you do not use a chuck key to open or close the jaws of a keyless chuck. Over time the teeth of a keyed chuck can break or chip, making the process of opening and closing a traditional chuck difficult, but keyless chucks do not suffer this fate.
Comparable quality keyless chuck drills cost more than those with keyed chucks. The mechanism that opens and closes a keyless chuck is more difficult to make, and the cost is passed on to the consumer. Both types are made of hardened steel, so they should last about the same length of time before having to be replaced; therefore, the overall cost of ownership is slightly higher with keyless models. You can get a quality medium-size drill with a keyless chuck for roughly $75.
When using a drill for milling or making precision holes that must be within a small tolerance, the amount of runout is important. Most experts and machinists would agree that keyed chucks are more accurate related to overall runout with some models as little as .0006 inch. The jobs where the holes have no specific tolerance and are used for clearance allows the use of a keyless drill chuck for quick changes on manual milling machines. Runout is not a factor for drilling with a hand drill in most cases.
Keyless chucks can only be spun clockwise as the drill would automatically come loose if it were used counterclockwise. This limits the use with tools other than standard twist drills and end mills for machining and drilling operations. Some machinists use tools that need to be spinning counterclockwise and will have to use keyed chucks in this instance. Some computer numerical control (CNC) lathes and CNC mills demand that the tool be spinning counterclockwise, so many machinists prefer to use keyed chucks for these operations.