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    CHUCKS

    A chuckis a specialized type ofclamp used to hold an object,[1]

    usually an object withradial symmetry,especially acylindrical object. It is most commonly used to hold a rotating tool (such as thedrill bit in apowool)or a rotating workpiece (such as thebaror blank in the headstockspindle of alathe). Some chucks c

    also hold irregularly shaped objects (ones that lack radial symmetry). In some applications, the tool orworkpiece being held by the chuck remains stationary while another tool or workpiece rotates (for exampla drill bit in the tailstock spindle of a lathe, or a round workpiece being milled by a milling cutter).

    Many chucks havejaws, which aredogs that are arranged in a radially symmetrical pattern (like the pointof astar)to hold the tool or workpiece. Often the jaws will be tightened or loosened with the help of a chukey, which is awrench-like tool made for the purpose. Many jawed chucks, however, are ofhe keylessvariety, and their tightening and loosening is by hand force alone. Keyless designs offer the

    convenience of quicker and easier chuckingand unchuckingat the expense of higher gripping force tohold the tool or workpiece. Collet chucks, rather than having jaws, havecollets,which are flexible collarssleeves that fit closely around the tool or workpiece and grip it when squeezed.

    A few chuck designs are more complex yet, and they involve specially shaped jaws, higher numbers of jaquick-release mechanisms, or other special features.

    Some chucks, such as magnetic chucks and vacuum chucks, are of a different sort from the radiallysymmetrical mechanical clamps mentioned above. Instead, they may be surfaces (typically flat) againstwhich workpieces or tools are firmly held bymagnetic orvacuum force.

    To chucka tool or workpiece is to hold it with a chuck, in which case it has been chucked.Machining wowhose workholding involves a chuck is often called chucking work.Automatic lathes that specialize inchucking work are often called chuckers

    Self-centering

    A self-centering chuck, also known as a scroll chuck,[2]usesdogs (usually calledjaws), interconnected via scroll gear(scroll plate), to hold onto a tool or workpiece. Because they most often have three jaws, theerm three-jaw chuckwithout other qualification is understood by machinists to mean a self-centering threeaw chuck. The term universal chuckalso refers to this type. These chucks are best suited to grip circular hexagonal cross-sections when very fast, reasonably accurate (0.005 inTIR)centering is desired.

    Sometimes this type of chuck has four or six jaws instead of three. More jaws confer more secure grip (if work is truly cylindrical) and thin-walled work will deform less. Four jaws are also useful for square bar wo

    ndependent-jaw (non-self-centering) chucks with three jaws also can be obtained.

    There are hybrid self-centering chucks that have adjustment screws that can be used to further improve t

    concentricity after the workpiece has been gripped by the scroll jaws. This feature is meant to combine thspeed and ease of the scroll plate's self-centering with the runout-eliminating controllability of anndependent-jaw chuck. The most commonly used name for this type is a brand name, Set-Tru. To avoidunduegenericization of that brand name, suggestions for a generic name have included "exact-adjust".[3]

    Three-jaw chucks can often be found on lathes andindexing heads.

    http://en.wikipedia.org/wiki/Clamp_(tool)http://en.wikipedia.org/wiki/Chuck_(engineering)#cite_note-0http://en.wikipedia.org/wiki/Chuck_(engineering)#cite_note-0http://en.wikipedia.org/wiki/Chuck_(engineering)#cite_note-0http://en.wikipedia.org/wiki/Rotational_symmetryhttp://en.wikipedia.org/wiki/Cylinder_(geometry)http://en.wikipedia.org/wiki/Drill_bithttp://en.wikipedia.org/wiki/Power_toolhttp://en.wikipedia.org/wiki/Power_toolhttp://en.wikipedia.org/wiki/Bar_stockhttp://en.wikipedia.org/wiki/Spindle_(tool)http://en.wikipedia.org/wiki/Lathe_(metal)http://en.wikipedia.org/wiki/Milling_cutterhttp://en.wikipedia.org/wiki/Dog_(engineering)http://en.wikipedia.org/wiki/Star_(polygon)http://en.wikipedia.org/wiki/Wrench#Other_types_of_keyshttp://en.wikipedia.org/wiki/Collethttp://en.wikipedia.org/wiki/Magnethttp://en.wikipedia.org/wiki/Vacuumhttp://en.wikipedia.org/wiki/Machininghttp://en.wikipedia.org/wiki/Automatic_lathehttp://en.wikipedia.org/wiki/Chuck_(engineering)#cite_note-1http://en.wikipedia.org/wiki/Chuck_(engineering)#cite_note-1http://en.wikipedia.org/wiki/Chuck_(engineering)#cite_note-1http://en.wikipedia.org/wiki/Dog_(engineering)http://en.wikipedia.org/wiki/Total_indicator_readinghttp://en.wikipedia.org/wiki/Genericized_trademarkhttp://en.wikipedia.org/wiki/Chuck_(engineering)#cite_note-Whitney2011-2http://en.wikipedia.org/wiki/Chuck_(engineering)#cite_note-Whitney2011-2http://en.wikipedia.org/wiki/Indexing_headhttp://en.wikipedia.org/wiki/Indexing_headhttp://en.wikipedia.org/wiki/Chuck_(engineering)#cite_note-Whitney2011-2http://en.wikipedia.org/wiki/Genericized_trademarkhttp://en.wikipedia.org/wiki/Total_indicator_readinghttp://en.wikipedia.org/wiki/Dog_(engineering)http://en.wikipedia.org/wiki/Chuck_(engineering)#cite_note-1http://en.wikipedia.org/wiki/Automatic_lathehttp://en.wikipedia.org/wiki/Machininghttp://en.wikipedia.org/wiki/Vacuumhttp://en.wikipedia.org/wiki/Magnethttp://en.wikipedia.org/wiki/Collethttp://en.wikipedia.org/wiki/Wrench#Other_types_of_keyshttp://en.wikipedia.org/wiki/Star_(polygon)http://en.wikipedia.org/wiki/Dog_(engineering)http://en.wikipedia.org/wiki/Milling_cutterhttp://en.wikipedia.org/wiki/Lathe_(metal)http://en.wikipedia.org/wiki/Spindle_(tool)http://en.wikipedia.org/wiki/Bar_stockhttp://en.wikipedia.org/wiki/Power_toolhttp://en.wikipedia.org/wiki/Power_toolhttp://en.wikipedia.org/wiki/Drill_bithttp://en.wikipedia.org/wiki/Cylinder_(geometry)http://en.wikipedia.org/wiki/Rotational_symmetryhttp://en.wikipedia.org/wiki/Chuck_(engineering)#cite_note-0http://en.wikipedia.org/wiki/Clamp_(tool)
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    Self-centering three-jaw chuck and key with one jaw removed and inverted showing the teeth that engagehe scroll plate. The scroll plate is rotated within the chuck body by the key, the scroll engages the teeth ohe underside of the jaws which moves the three jaws in unison, to tighten or release the workpiec

    ndependent-jaw

    ndependent four-jaw chuck, also known as a universal chuck, with

    he jaws independently set. The key is used to adjust each jaw

    separately.

    An older and larger 4 jaw chuck. Note how it is able to grip an

    rregularly cut piece of used metal. Though not found on small

    chucks it is common for larger chucks (the one in the second photo

    was made around 1900 and is 24" in diameter) to have many of the

    eatures of afaceplate.The jaws are stepped on one side and full

    height for gripping on the other and are reversible. Generally the jaws are usable for holding either outsid

    as shown here, or inside as in gripping the inside of a pipe.

    http://en.wikipedia.org/wiki/Lathe_faceplatehttp://en.wikipedia.org/wiki/File:FourJawChuckIndependent.jpghttp://en.wikipedia.org/wiki/File:FourJawChuckIndependent.jpghttp://en.wikipedia.org/wiki/Lathe_faceplate
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    On an independent-jaw chuck, each jaw can be moved independently. Because they most often have fouaws, the term four-jaw chuckwithout other qualification is understood by machinists to mean a chuck witour independent jaws. The independence of the jaws makes these chucks ideal for (a) gripping non-circucross sections and (b) gripping circular cross sections with extreme precision (when the last few hundredtof a millimeter [or thousandths of an inch] of runout must be manually eliminated). The non-self-centeringaction of the independent jaws makes centering highly controllable (for an experienced user), but at theexpense of speed and ease. Four-jaw chucks are almost never used for tool holding. Four-jaw chucks cabe found on lathes and indexing heads.

    Self-centering chucks with four jaws also can be obtained. Although these are often said to suffer from twodisadvantages: inability to hold hex stock, and poor gripping on stock which is oval, only the latter is true.Even with three jaw self centering chucks, work which is not of uniform section along the work (and whichnot free of spiral or 'wind')should not be gripped, as the jaws can be strained and the accuracy permanenmpaired.

    Four-jaw chucks can easily hold a workpiece eccentrically if eccentric features need to be machined.

    One may dispute if there really are advantages of using a three jaw chuck over a four jaw chuck. It may be that therere better times to use each type of chuck. As is discussed in other topics, four jaw chucks are used when the work

    equires it.

    The same thought should apply when discussing three jaw chucks. When the work requires that the part be loaded aunloaded with minimal amount of time and effort, then a three jaw chuck is a good choice.

    Three jaw chucks are also a good choice if there is a large quantity of parts to machine, and the operations beingperformed do not require a high degree ofprecisionorconcentricity.

    Since the jaws on a three-jaw chuck all move in unison, centering a cylindrical part is not a concern. The part will ru

    oncentric with the chuck, providing that there are no foreign particles between the jaws and the part, or that the chu

    s installed on thespindleproperly and the chuck has not worn irregularly.

    The jaw faces can also be reversed to accommodate larger diameters. You will notice in the video that the mechanis

    hat moves/guides the jaws is not removed or reversed. The jaw faces are simply reversed and keyed back into placetop the jaw guide

    There are certain disadvantages to using a three jaw chuck. Three jaw chucks get used a great deal resulting in a lot

    wear and tear on the chuck. Because of the wear and tear, there should be an appropriate amount of maintenanceperformed.

    Three jaw chucks are considered or assumed to run perfectly concentric, but often that is not the case. Chips get insi

    he faceplate of the chuck and into thescroll,where the jaws are connected to the chuck. These chips often cause the

    croll and the teeth of the jaw bottoms to bind, and eventually these parts will wear away and become less than perfe

    As a result, the chuck does not grip the part perfectly even andrun outcan occur.

    Three jaw chucks are limited in the size of parts that they can hold, and generally are not considered the best choice heavy duty machining is being performed.

    A drill chuck is a specialised self-centering, three-jaw chuck, usually with capacity of less than 0.5 in13 mm) and rarely greater than 1 in (25 mm), used to hold drill bitsor other rotary tools. This is the type o

    chuck that a machining layperson is most likely to be familiar with.

    http://www.jjjtrain.com/vms/glossary/p/precision.htmlhttp://www.jjjtrain.com/vms/glossary/p/precision.htmlhttp://www.jjjtrain.com/vms/glossary/p/precision.htmlhttp://www.jjjtrain.com/vms/glossary/c/concentric.htmlhttp://www.jjjtrain.com/vms/glossary/c/concentric.htmlhttp://www.jjjtrain.com/vms/glossary/c/concentric.htmlhttp://www.jjjtrain.com/vms/glossary/s/spindle.htmlhttp://www.jjjtrain.com/vms/glossary/s/spindle.htmlhttp://www.jjjtrain.com/vms/glossary/s/spindle.htmlhttp://www.jjjtrain.com/vms/glossary/s/scroll.htmlhttp://www.jjjtrain.com/vms/glossary/s/scroll.htmlhttp://www.jjjtrain.com/vms/glossary/s/scroll.htmlhttp://www.jjjtrain.com/vms/glossary/r/run-out.htmlhttp://www.jjjtrain.com/vms/glossary/r/run-out.htmlhttp://www.jjjtrain.com/vms/glossary/r/run-out.htmlhttp://en.wikipedia.org/wiki/Drill_bithttp://en.wikipedia.org/wiki/Drill_bithttp://en.wikipedia.org/wiki/Drill_bithttp://en.wikipedia.org/wiki/Drill_bithttp://www.jjjtrain.com/vms/glossary/r/run-out.htmlhttp://www.jjjtrain.com/vms/glossary/s/scroll.htmlhttp://www.jjjtrain.com/vms/glossary/s/spindle.htmlhttp://www.jjjtrain.com/vms/glossary/c/concentric.htmlhttp://www.jjjtrain.com/vms/glossary/p/precision.html
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    Some high precision chucks use ball thrust bearings to reduce friction in the closing mechanism andmaximizing drilling torque. One brand name for this type of chuck, which is often genericized in colloquialuse although not in catalogs, is Super Chuck.

    Apin chuckis a specialized chuck designed to hold small drills (less than 1 mm (0.039 in) in diameter) thcould not be held securely in a normal drill chuck. The drill is inserted into the pin chuck and tightened, thepin chuck is then inserted into the larger drill chuck so that the operation can continue. Pin chucks are alsound on high speed rotary tools, such asdie grindersandjig grinders

    Top: an assembled keyless chuck. The tightening action of this chuck style is

    performed by twisting the body using firm hand pressure only. While convenient, this feature can cause th

    chuck to loosen if too muchtorqueis applied. Bottom: the traditional keyed style of drill chuck with its key

    Thearboris shown separately to the right. These chucks require a key to provide the necessary torque to

    ghten and loosen the jaws. The rotary action of the key turns the outer body which acts on an internal

    screw; this in turn moves the threaded jaws in or out along a tapered surface. The taper allows the jaws to

    encompass various sizes ofdrill shanks.The end view shows the three small jaws that slide within the bo

    http://en.wikipedia.org/wiki/Die_grinderhttp://en.wikipedia.org/wiki/Die_grinderhttp://en.wikipedia.org/wiki/Die_grinderhttp://en.wikipedia.org/wiki/Jig_grinderhttp://en.wikipedia.org/wiki/Jig_grinderhttp://en.wikipedia.org/wiki/Jig_grinderhttp://en.wikipedia.org/wiki/Torquehttp://en.wikipedia.org/wiki/Torquehttp://en.wikipedia.org/wiki/Torquehttp://en.wikipedia.org/wiki/Arbor_(tool)http://en.wikipedia.org/wiki/Arbor_(tool)http://en.wikipedia.org/wiki/Arbor_(tool)http://en.wikipedia.org/wiki/Drill_bit_shankhttp://en.wikipedia.org/wiki/Drill_bit_shankhttp://en.wikipedia.org/wiki/Drill_bit_shankhttp://en.wikipedia.org/wiki/Drill_bit_shankhttp://en.wikipedia.org/wiki/Arbor_(tool)http://en.wikipedia.org/wiki/Torquehttp://en.wikipedia.org/wiki/Jig_grinderhttp://en.wikipedia.org/wiki/Die_grinder