Sheet1Design Guideline For ColletsINDEXIntroduction/ Index1Clamping diameter of collet2Other data3Slits (number ,width ,flattening)Types of component & slits positionSlits (length of slits & collet wallthickness)Slits forms4Collet exapansion values5Free bore details6Longitudinal grooves7Gripping bore8Type of collets9Material used for collets10Heat treatment11Collet expansion (process)12Sepcial manufacturing instruction13Calculating clamping force generated in collet clamping14Checking of collets15Typical drawing of colletsTraub AFortunaHMT ASH 160HMT TR 42

Sheet2Design Guideline For ColletsPage 11Clamping dia for standard colletsOn the finished drawing , the maximum clamping for any size is specifiedIt is to be noted that for automatic collets the max through hole depends on themax clamping of the concerned feed finger (feed collet )1.1Collets should not be used for diameter > 0.1 mm than the max. diameter forwhich it is to be designed2Other data on all finished as per following fig. 1fig 13.1Slit: Number , Width ,Flattening see fig.2Shaft Dcollet with shaft D3/4 Lcollet with shaft D 3/4 LBreadthFlattening on taper lengthfromuptoHexOctHexOctbB-203343341*320303343341.2430403343341.6540504343342650604344342.2760804644342.58801004644343101001206684343.512120150668468412*Collets for clamping

Sheet3Design Guideline For ColletsPAGE 23.2Types of component & slits position3.3Slits : Length of slits & wallthicknessFor fig 9Length of slitWallthicknessaboveuptot15115301.230401.440501.650601.860802801002.510012031201503.51504For fig 9Shaft D5101520253035405060708090100120150Length of slit l1530405060708090100110120130135140145150

Sheet4Design Guideline For ColletsFig 10Collets upto 40 free bore in which the material is fed from behind withoutfeeding bar (Turret)Fig 11collets in which the material is fed from frontFig 12Collets with free bore > 40 in which the material is fed from behind withoutfeedrod as well as automatics colletsFig 13Collets on lathe with collet head

Sheet3 (2)Design Guideline For ColletsPAGE 43.3SLITS (FORM)*Collets up to 20 mm get only slits (fig 10)*Collets above 20 mm get slits with slots ( fig 11)shaft baboveupto2040540606608088011010110.12*Collets in which the length is small in relation to the collet get a longitudinal & crosswise slit4Collet Expansion Values( For collet expansion process see 11.0 page 8 )shaft daboveuptoaboveuptoaboveuptoaboveuptoaboveupto121240408080120120collet0.5 +0.31 +0.51.5 +0.52 +0.53 +0.5expansion

Sheet3 (3)Design Guideline For ColletsPAGE 55Free Bore Details :For fig 13 14 15Free BoreaRaboveupto5.5101.55.57.51027.59.51239.514.7514414.752416524322083240201040602515608025208012030201201503520For fig 16Shaft Clamping KRupto302019540301955040191060502410756324109078241011010024101301202410

Sheet3 (4)Design Guideline For ColletsPAGE 66Longitudinal Grooves :In collets for profile bars, longitudinal slots as per fig.11 should be providedA/Faboveup toaboveup toaboveup toaboveup toaboveup to55101020204040.Hex0.6*0.41*0.81.2*0.81.8*12*1.2oct1.6*0.82*1.07Gripping Bore:for collets used on multispindle longitudinal & transverse grooves are provided. Form of grooves as per fig 12Transverse grooves for profile bars as per fig 13longitudinal grooves for round clamping bars as per fig 14A/Faboveup toaboveup toaboveup to2030304040A/F+1.2A/F+1.8A/F+2.5clamping aboveup toaboveup toaboveup to1025253636No of grooves369x604080

Sheet3 (5)Design Guideline For ColletsPAGE 78TYPE OF COLLET1Push type*Single conefig 17*Double conefig 182Pull typefig 193Internal expandingfig 20

Sheet3 (6)Design Guideline For ColletsPAGE 89Material:Collets are made out of following materialsC=0.55 - 0.68, Mn=0.74 - 1.26, Si= 0.76 - 1.041En 45A2DIN 1.28263IS:3749 ~ T55 Si 74BOHLER SP CS (C=0.6, Si=0.9,Mn=0.4, Cr=1.2, V= 0.1 )10HEAT TREATMENT :1Clamping portion to HRc 54.562Stock portion tempered to blue ,red yellow resp. from guide D to clamping area3Collet Expansion is done as a last operation (i.e. after finish bore grinding &slitting off the small portion near bore )the collet is heated by flame near the slit ends gradually & universally by rotatingon a cone with diameter markings. After heating the collet is pressed from top tillthe front diameter is expanded uniformly to a desired value. The collet is cooleddown on the fixture to room temperatureSmaller collet are uniformly hardened & tempered to HRc 4245 throughout the lengthNo selective or gradual hardening is carried out.

Sheet3 (7)Design Guideline For ColletsPAGE 912Special Manufacturing Instructions :12.1No turning lines ,deep tool marks, serrations etc are to be permitted on collets.All sharp edges to be rounded off smoothly.12.2Radial runout of the clamping bore to be measured w.r.t. stock dia (Guide dia. )beforeopening off the slits completely12.3No. of slits & division should be made equispaced within 5" to ensure maintaining T.R. withinclose specification & collet T.R. accuracy12.4collet are provided with hard rubber , polyurethane material stoppers to prevent loose chips ,coolant etc entry thro the slits inside the collets fig 16small or thin walled collets may be co tempered instead of hardened in oil , at a temperatureabout 250 c.The additional tempering of the clamping end ,to spring hardness is best effected bycutting it stand on glowing plate or submerging it in a lead bath .For Bohler SPCS the correct tempering temperature is 480c to 500c12.5Typical Manufacturing & heat treatment of collet*Finishing with grinding allowance on the fitting parts, including boring , finish threadingor tapping*mill the slots, leaving a narrow thward at each slot near chucking part so that thedistortion during hardening is largely avoided

Sheet3 (8)Design Guideline For ColletsPAGE 10Fig 23*Harden at temp. mentioned abovequenching in oil or austempering*Temper the whole collet at 220c to 240c*Temper the chuckend only. At the process described above the heat falls off graduallyon one end to the other the tempering temperature may be guessed from temperingcolor therefore the surface should be rubbed bright with emery & care should betaken that heating is uniform around the circumference when tempering has progressedfor enough (about halfway down the chuck lips ) cool the whole collet rapidly inquench oil*Finish Grinding ( stock or locating diameter & taper w.r.t. collet axis by clamping thecollet between centers made on pre-bore & free-bore ends in slot stage )Then taking reference of locating diameter grind the bar clamping bore which is usuallythe max limit of the component to be clamped in the collet*Finally the parts of thwards left tending between the slots & remove burr from slot ends*Expand the collet (see procedure on collet expansion )

Sheet3 (10)Design Guideline For ColletsPAGE 1113Calculating the Clamping force in collet :Action of clamping forces in colletClamping forces W developed by the collet is determined as follow :Force Q produced by a drive ( a pneumatic cylinder or manually ) acts upon a collet along its axis0-0 . Suppose the collet is having n number of jaws; each jaw will receive a part of force Q=Q'/n&will act like a wedge mechanism.Each force Q/n produces reaction force Q'/n The conical surface E-H takes up reactionforce R/n where R is the resultant force in the force triangle ABC.The part W'/n is found from theforce triangle ABCW'/n = Q'/ntan xhenceW'=Q'/tan xsince W'=W & Q'=QW=Q/tan xkgf ( N )

Sheet3 (11)Design Guideline For ColletsPAGE 12In operation , the collet is subject to friction on its taper surface E-H & on its whole surfaceIn addition, a force needed to flex the jaws & a force needed to compress the return springshould be taken into accountThenW= Q{1/ tan (x + Q1)+tan Q2} - (T+F)with a collet chuck without the workpiece stopW= Q{1/ tan (x + Q1)} - (T+F)whereQ1=angle of friction on chuck & collet surfacesQ2= angle of friction on collet hole & workpiece surfaceT=force of flexing collet jawsF=force of compressing return springsForce T can be assumedcollet T kgfaboveup to305103050102550802550Force F is found from spring diagramThe angle of friction Q1 & Q2 are taken 543' each.

MBD0013F10C.unknown

MBD00145B4B.unknown

MBD001D7396.unknown

MBD0020FBAB.unknown

MBD001D2EF5.unknown

MBD0014112F.unknown

MBD00135E8C.unknown

MBD001377BF.unknown

MBD0013B88B.unknown

MBD00136D90.unknown

MBD00127E92.unknown

MBD0012BCBF.unknown

MBD0013421D.unknown

MBD00129E01.unknown

MBD001216C9.unknown

MBD00125227.unknown