A par­al­lel key con­nec­tion is used to ef­fect a shaft-hub con­nec­tion (see pic­tu­re). It is the most com­mon­ly used form-lo­cking con­nec­tion for pul­leys, gear wheels and cou­plings wi­th shafts wi­th pre­do­mi­nant­ly one-si­ded tor­que load. This ty­pe of con­nec­tion is cost-ef­fec­ti­ve, ea­sy to mount and ea­sy to re­lease. The par­al­lel key sits in the shaft and hub key­way and acts as a dri­ver but, in con­trast to the struc­tu­ral­ly si­mi­lar slot wedge con­nec­tion, is on­ly load-bea­ring la­te­ral­ly, the rear sur­face ha­ving a de­gree of play. Par­al­lel key con­nec­tions are pu­re dri­ve-ty­pe con­nec­tions. In con­trast to the wedge con­nec­tion, the parts are not clam­ped firm­ly tog­e­ther. The­re must al­ways be cle­arance bet­ween the par­al­lel key and the bot­tom of the hub key­way (see pic­tu­re). The par­al­lel la­te­ral sur­faces of the par­al­lel key lie against the la­te­ral sur­faces of the shaft and hub key­way and so trans­mit the tor­que load bet­ween shaft and hub th­rough a tight fit. The par­al­lel key func­tions by sur­face pres­su­re and shea­ring. To avo­id the per­mis­si­ble strength va­lues be­ing ex­cee­ded, the length of the par­al­lel key should be at least 1.2 times grea­ter than the dia­me­ter of the shaft.

The ad­van­ta­ges of a par­al­lel key con­nec­tion are its high ac­cu­ra­cy, the cen­tral lo­ca­ti­on of the hub, the lack of can­ting and ten­sio­ning, the lack of any need to fit and dri­ve in as wi­th wed­ges and the re­sul­ting lack of da­ma­ge to the com­pon­ents (im­portant if rol­ling bea­rings are be­ing built in). The on­ly re­al di­s­ad­van­ta­ges are that the hubs must be ad­di­tio­nal­ly pro­tec­ted against axi­al dis­pla­ce­ment and their vul­nerabi­li­ty to mu­tu­al tor­que. The ad­van­ta­ges, ho­we­ver, si­gni­fi­cant­ly out­weigh the disadvantages.

The stan­dards for par­al­lel keys by pat­tern and di­men­si­ons are set by DIN 6885. The pic­tu­re be­low shows the dif­fe­rent pat­terns of par­al­lel keys de­li­ver­ed by Crum­men­erl GmbH.

Cus­tom di­men­si­ons and pat­terns are pos­si­ble. DIN 6885 al­so sti­pu­la­tes that a fit wi­th the to­le­rance field P9, N or JS9 in ac­cordance wi­th DIN 7155 must be used for the to­le­rance of the slot width. The par­al­lel key the­r­e­fo­re is equi­va­lent to a uni­form shaft wi­th to­le­rance po­si­ti­on h (up­per de­via­ti­on = 0). The ba­ses for the de­sign and cal­cu­la­ti­on of par­al­lel key con­nec­tions are set out by DIN 6892. Par­al­lel keys in pat­tern A and B are available wi­th tap­ped ho­les for for­cing screws, pat­terns E and F al­so wi­t­hout such tap­ped ho­les. In pat­terns E and F the for­cing screw is lo­ca­ted to one si­de and not cen­tral­ly. This en­ables le­vera­ge, which fa­ci­li­ta­tes the re­lease of the par­al­lel key from the slot.

The most com­mon­ly used ma­te­ri­al to­day is C45K. Crum­men­erl GmbH ma­nu­fac­tures par­al­lel keys in this ma­te­ri­al in lar­ge quan­ti­ties but al­so makes them from 34CrNiMo6, 42CrMo4 (for grea­ter load-bea­ring), Ni­ros­ta and other spe­cial al­loys. In spe­cial ca­ses, ti­ta­ni­um al­loys are al­so used. Ad­he­rence to fac­to­ry stan­dards and spe­cial heat tre­at­ments are stan­dard to us

A par­al­lel key con­nec­tion is used to ef­fect a shaft-hub con­nec­tion (see pic­tu­re). It is the most com­mon­ly used form-lo­cking con­nec­tion for pul­leys, gear wheels and cou­plings wi­th shafts wi­th pre­do­mi­nant­ly one-si­ded tor­que load. This ty­pe of con­nec­tion is cost-ef­fec­ti­ve, ea­sy to mount and ea­sy to re­lease. The par­al­lel key sits in the shaft and hub key­way and acts as a dri­ver but, in con­trast to the struc­tu­ral­ly si­mi­lar slot wedge con­nec­tion, is on­ly load-bea­ring la­te­ral­ly, the rear sur­face ha­ving a de­gree of play. Par­al­lel key con­nec­tions are pu­re dri­ve-ty­pe con­nec­tions. In con­trast to the wedge con­nec­tion, the parts are not clam­ped firm­ly tog­e­ther. The­re must al­ways be cle­arance bet­ween the par­al­lel key and the bot­tom of the hub key­way (see pic­tu­re). The par­al­lel la­te­ral sur­faces of the par­al­lel key lie against the la­te­ral sur­faces of the shaft and hub key­way and so trans­mit the tor­que load bet­ween shaft and hub th­rough a tight fit. The par­al­lel key func­tions by sur­face pres­su­re and shea­ring. To avo­id the per­mis­si­ble strength va­lues be­ing ex­cee­ded, the length of the par­al­lel key should be at least 1.2 times grea­ter than the dia­me­ter of the shaft.

The ad­van­ta­ges of a par­al­lel key con­nec­tion are its high ac­cu­ra­cy, the cen­tral lo­ca­ti­on of the hub, the lack of can­ting and ten­sio­ning, the lack of any need to fit and dri­ve in as wi­th wed­ges and the re­sul­ting lack of da­ma­ge to the com­pon­ents (im­portant if rol­ling bea­rings are be­ing built in). The on­ly re­al di­s­ad­van­ta­ges are that the hubs must be ad­di­tio­nal­ly pro­tec­ted against axi­al dis­pla­ce­ment and their vul­nerabi­li­ty to mu­tu­al tor­que. The ad­van­ta­ges, ho­we­ver, si­gni­fi­cant­ly out­weigh the disadvantages.

The stan­dards for par­al­lel keys by pat­tern and di­men­si­ons are set by DIN 6885. The pic­tu­re be­low shows the dif­fe­rent pat­terns of par­al­lel keys de­li­ver­ed by Crum­men­erl GmbH.

Cus­tom di­men­si­ons and pat­terns are pos­si­ble. DIN 6885 al­so sti­pu­la­tes that a fit wi­th the to­le­rance field P9, N or JS9 in ac­cordance wi­th DIN 7155 must be used for the to­le­rance of the slot width. The par­al­lel key the­r­e­fo­re is equi­va­lent to a uni­form shaft wi­th to­le­rance po­si­ti­on h (up­per de­via­ti­on = 0). The ba­ses for the de­sign and cal­cu­la­ti­on of par­al­lel key con­nec­tions are set out by DIN 6892. Par­al­lel keys in pat­tern A and B are available wi­th tap­ped ho­les for for­cing screws, pat­terns E and F al­so wi­t­hout such tap­ped ho­les. In pat­terns E and F the for­cing screw is lo­ca­ted to one si­de and not cen­tral­ly. This en­ables le­vera­ge, which fa­ci­li­ta­tes the re­lease of the par­al­lel key from the slot.

The most com­mon­ly used ma­te­ri­al to­day is C45K. Crum­men­erl GmbH ma­nu­fac­tures par­al­lel keys in this ma­te­ri­al in lar­ge quan­ti­ties but al­so makes them from 34CrNiMo6, 42CrMo4 (for grea­ter load-bea­ring), Ni­ros­ta and other spe­cial al­loys. In spe­cial ca­ses, ti­ta­ni­um al­loys are al­so used. Ad­he­rence to fac­to­ry stan­dards and spe­cial heat tre­at­ments are stan­dard to us