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==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 [[Drill bit|bits]].
* Loss of the key wastes time if not attached to the [[flex|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 bit]]s 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 [[flex|mains lead]] with a cable tie to
avoid wasted time searching for it.


===Removal===
# Open the chuck jaws wide.
# 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.
# Insert chuck key, or attach [[Clamps|locking pliers]] to the top of
a keyless chuck
# 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===
# Remove chuck from the drill,
# 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]].
# 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 jsut
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 hex hole. ways to do
this include:
# place 2 small screws inside, the first one head first, the 2nd point
first. Tighten the 2nd screw down firm with a screwdriver. The
[[screw]]s need to be the right width for this to work.
# 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
off dead drills.


==See also==
* [[Drill bit]]
* [[Hex bit]]


[[Category:Tools]]
[[Category:Repair]]