Slide bearings - Wolf Kunststoff-Gleitlager GmbH

CCCCCC5.1.1.4. Bearing wall thickness (sk) subjectedto edge pressureWe recommend to use thick-walled bushings in casethe construction of the bearing seat is subjected to errorsin geometry and misalignments in order to achieve alower spring constant on the wall of the slide bearingbush, which in this case also works as a spring dampingelement. This causes better deformations (adaptation ofthe bushing to the incorrect geometry) and therefore areduction of stress as well as an increase of workinglife.5.1.2. Bushing width bThe bushings most frequently used in practice have amaximum width of about 0,8 up to 1,2 x screw diameter.This is due to the high costs of production (in general, awide bearing bush is more expensive than two halfbushings) and to the specific dynamic load-carryingcapacity.The bigger the proportion b / d, the lower the specificdynamic load-carrying capacity of a slide bearing bush(see ill. 26), because the danger of overheating (causedby the accumulation of heat in the middle of the slidebearing bush) rises with an increasing bushing width.5.2. Bearing clearance5.2.1. Inside diameter of the bushing afterinstallationThe slide bearing bushes are available in four differentclasses of bearing clearances.According to stress exerted on the application and itsdemand of accuracy you can chose either a big (D), asmall (F) or even a negatively (N) constructed (includingpre-stressing) installation bearing clearance.All standard designed slide bearing bushes (abbreviation“C”) show an inside diameter with the ISO-tolerance D8after stuffing them into the casing with a tolerance H5.The dimension list shows the maximum and minimumdiameters (d1 maxor d1 min) respective to this class ofbearing clearances.Please take the figures for the other classes of bearingclearances from the ISO-tolerance table.When using casings of bigger tolerance ranges the holeof the stuffed slide bearing bush increases accordingly(see page 12).Bearing clearance5.2.2. Screw diameterThe tolerance of the screw diameter must not exceedthe nominal dimension, for it may not fall below theminimum installation bearing clearance. Therefore,according to the ISO-standard, the tolerance ranges “a”to “h” are suited for the screw. Concerning the quality ofthe screw, we recommend the ISO-tolerance class 6 to7.We recommend an ISO-tolerance of h6 or h7 as astandard tolerance of the screw.When operating with screws of other dimensionaldeviations the inside diameter of the slide bearing bushcan be matched accordingly, in order to achieve therequired clearance (see preface ).5.2.3. Installation bearing clearanceThe installation bearing clearance is determined by thedimensions of the slide bearing hole ø d1in the moldedstate and by the tolerance of the screw diameter. Theinstallation bearing clearance is measured in a standardconditioning atmosphere (20°C and 50 % rF) after stuffingthe slide bearing bush into the bearing seat with anISO-quality of H5 in the operational state.The minimum and maximum installation bearingclearance yields from the following formulas:Se min = ød1min - Ao screw [ 4]Se max= ød1 - Au screw [5]maxin which:Se = installation bearing clearanceAu = lower dimensional deviationAo = upper dimensional deviationød1max = taken from formula [2]ød1 = taken from the dimension listsminThe question, whether slide bearing bushes with areduced installation bearing clearance are suited for yourapplication, depends on the stress and will be settled inthe course of the slide bearing calculation (see chapter12.2.).PrefaceContentsMaterialoverviewIndex Slide bearings Slide bearings Conditions ofTribologyMathematical Design(with collar) (cylindrical) installationexample guidelinesWolf Kunststoff-Gleitlager GmbH • Heisenbergstr. 63 - 65 • 50169 Kerpen-Türnich • Tel. 02237/9749-0 • Fax. 02237/9749-2016