Chuck

Overview

Keyed chuck

The traditional drill chuck used for most of the 20th century.

• Slower & less convenient to use than keyless.
• Level of grip with these is consistently good, but there are situations in which they can come loose, mainly with hammer action and large bits.
• Loss of the key wastes time if not attached to the mains lead (the key fairy is mischevious).

Keyless Chuck

Quick & easy to use, these are a real convenience advantage over keyed chucks.

However there are several subtypes of keyless chuck, with performance among such chucks inconsistent.

Some keyless chucks give poor grip compared to keyed, often coming loose, especially with hammer action. Some can occasionally overtighten in use, making bit removal very difficult. Some keyless chucks are prone to come loose when operating anticlockwise. Some are very good, particularly locking keyless chucks, which can perform even better than keyed chucks.

There are also 2 styles of sleeve arrangement:

• 2 part sleeve: requires 2 hands to operate
• single sleeve: requires one hand to operate. To get maximum tightening, set the drill to its lowest gear.

SDS

SDS offers massive performance advantages over the older types of chuck in hammer mode. There are 2 SDS chucks in use:

• SDS, SDS+: 2 slightly different names for the exact same thing. Most SDS chucks are this size
• SDS max: larger heavier duty version of SDS, used mainly on handheld breakers

Hex

Great for instant bit changes, but otherwise the worst performing chuck type

• take a wide array of screwdriving, drilling & nutdriving bits, plus others
• only takes hex based bits
• small & light
• side to side waggle
• hex shank drill bits are prone to breaking and spinning
• drill bits fall out of non-locking hex chucks in use

Types:

• Locking - pull back sleeve to release bit
• magnetic - bit just pulls out, but drill bits tend to get left in the workpiece. Good for screws, not good with drill bits.
• sprung - bits pull out easily, again not good for drill bits

Keyed chucks

Keys

There are different key sizes. If you get a multi-headed replacement key, it saves time to put some paint on the bit that fits.

The key can be attached to the mains lead with a cable tie to avoid wasted time searching for it.

Removal

1. Open the chuck jaws wide.
2. Unscrew the screw down the centre between the jaws. These often have a reverse thread and can be very tight. A manual impact driver can be useful.
3. Insert chuck key, or attach locking pliers to the top of a keyless chuck
4. Tap the key with a hammer to unscrew the chuck from the drill

Repair

Whether the chuck is sticking, loosening unwantedly or the jaws are out of position, the repair procedure is much the same. Remove the chuck from the drill, remove its outer cover, and clean the parts up.

Application of oil where not appropriate can result in chucks coming undone when they shouldn't.

In some cases its possible to reassemble a broken key ring and have the chuck then work fine long term. I did this once, and have had no problem with it. The broken parts are kept in place by the outer cover, and it works perfectly.

Disassembly

1. Remove chuck from the drill,
2. Clamp the outer body of the chuck near the drill-ward end (don't clamp near the key tightening ring), ideally in a vice in 2 indented bits of wood.
3. Tap the stem towards where the drill bit tip would be, to push the chuck assembly out from the outer cover

The mechanism is simple, and self assembly is fairly self evident.

Keyless Chuck

Jammed keyless chuck

If the chuck jams with a bit in it, apply a strap clamp to the sleeve, and tap it round with a mallet. Its often possible to stop the drill's shaft rotating by sticking something into the drill motor's cooling fan, the drill of course should be unplugged.

Hex Chuck

These are trivial to replace and not worth repairing. There is just one issue sometimes found: some chucks are designed for use with 2" bits only, and the more common 1" bits sit too deep in the chuck to use. The solution is to reduce the depth of the hexagonal hole. Ways to do this include:

1. place 2 small screws inside, the first one head first, the 2nd point first. Tighten the 2nd screw down firm with a screwdriver. The screws need to be the right width for this to work.
2. place a sheared off part of a hex bit in, with folded paper down one side. Force it down. You must get the size right first time, its not possible to remove it if its wrong.

SDS Chuck

These need greasing very occasionally.

Replacement

Replacing a chuck is a fairly easy job, and doesn't cost much.

• For keyed & keyless chucks, ensure the replacement is the right size of thread, and takes a suitable maximum size of tools.
• Some chucks are unsuitable for hammer use, and non-SDS hammerable chucks are unsuitable for SDS use in hammer mode (SDS applies much greater forces).
• Single sleeve keyless chucks rely on the drill motor not turning while being undone. Fitting one to an old drill that turns easily can make it very hard to undo. In such cases pick a 2 sleeve chuck or a keyless.
• Screw-on chucks with no central fixing screw will tighten themselves to the drill shaft.
• When a central fixing screw is used, ie in most cases, attach locking pliers to the chuck or insert the key, and tap it to tighten. Then open the jaws and fit the central screw firmly.
• Drills that don't use a screw-on chuck also exist.

Chucks are available from the usual builders' merchants, or can be had from dead drills.

Chuck adaptors

Some chuck adaptors have issues:

• adaptors with a hex shank increase bit wobble
• adaptors with an SDS shank are totally and utterly unable to handle sds hammering. Don't try it even for a moment, or you'll find out how chucks are made.

See also

• Drill bit
• Hex bits