ASME B94.33:1996 pdf download JIG BUSHINGS
1 SCOPE
This Standard covers the American National Standardpractice for sizes types. tolerances, and identification ofjig bushings and locking devices used for securing thebushings in the jig or bushing plate.
2 PURPOSE
The purpose of this Standard is to provide the necessary information for the design, procurement, and installation of jig bushings.
3 GENERAL
3.1 Press Fit Bushings
Press fit bushings to guide the tool are installed di-rectly in the jig without the use of a liner, and are employed principally where the bushings are used for shortproduction runs and will not require replacement. Theyalso are intended for use where the closeness of the cen.ter distance of holes will not permit the installation ofliners and renewable bushings. Press fit bushings aremade in two types: with heads and without.
3.2 Renewable Bushings
Renewable bushings to guide the tool are for use inliners, which in turn are installed in the jig. They are usedwhere the bushings will wear out or become obsolete before the jig or where several bushings are to be inter-changeable in one hole. They are usually made with aknurled head to facilitate removal.
There are “fixed”and “slip” milled notches combinedon the head of renewable bushings. There is one type ofrenewable bushing: slip-fixed renewable.
(a) The fixed side of the rcnewable bushing is usedwith the intention of leaving it in place until worn out.(b) The slip side of the renewable bushing is used withthe intention of changing it frequently in a given size ofliner. This side is most often used where two or more operations requiring different inside diameters are per.
formed in a single jig, such as where drilling is followedby reaming, tapping, spot facing, counterboring, or someother secondary operation.
3.3 Liner Bushings
Liner bushings are provided with and without headsand are permanently installed in a jig to receive the re-newable bushings. They are sometimes called “masterbushings.”
3.4 Bushing Specifications
The dimensions and tolerances of jig bushings shallconform to the specifications given in the tables and noteson the following pages.
3.5 Jig Plate Thickness
The standard lengths of the press fit portion of jig bushings as established are based on standardized uniform jigplate thickness.
4 JIG BUSHING DESIGNATION SYSTEM
4.1 Inside Diameter
Specify jig bushing by inside diameter of hole size, ina decimal dimension.
4.2 Bushing Type
Specify bushing type by using letter abbreviation asfollows:
(a)SF: Renewable, Slip-Fixed
(b) L: Liner, Plain
(c)HL: Liner, Headed
(d) P: Press Fit, Plain
(e) H: Press Fit, HeadedCarbide bushings should use the letter “C” after thetype designation (e.g. a slip-fixed renewable carbidebushing would be designated SFC)
ASME B94.33:1996 pdf download
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