Support
The smaller bushes are supplied with three or four holes , and the larger with five . Note : in some instances the fourth hole of the smaller bush , which is located so as to run into the split , is there for providing balance only . You therefore should never use this hole , either for fastening or for removal of the bush .
In the smaller size of taper bushes , two holes are used for fastening and one for removal and in the larger taper bushes , three holes are used for fastening , and two are used for removing the bush .
Note that it is common that the grub screws are BS Whitworth . If screws get lost , obtain a proper replacement from the supplier .
The entire taper lock bush and the bore of the hub are supplied with a protective anti-rust coating . This must be removed as the safe and secure operation depends on metal to metal contact , without any grease or oil remaining behind on the surfaces . Use a solvent to clean up the components . It is good practice that a taper lock bush should always be fitted with a key .
With regards to the the fitting of a parallel key ; the key must be an interference fit in the sides of the keyway , it must have a transition fit in the sides of the bush keyway and a clearance fit at the top of the keyway .
If a parallel key , which offers no top clearance is fitted , the bush will ride on this , and will not seat correctly on the shaft . Stresses will be set up , with stress concentrations at the corners of the keyway . In time , if not immediately , cracks will appear . If left , these will progress more and more deeply into the bush . Any bush which has any sign of cracking must be discarded .
Inspect the shaft and key carefully for burrs , and remove if necessary , to ensure that the bush will go onto the shaft without obstruction . Having checked the key size regarding the required top clearance and transition fit at sides of the bush keyway ; fit the key to the shaft keyway . Here it should be an interference fit .
INSTALLATION When installing the taper bush , line up the holes in the bush and the hub , and insert the bush . Place a small drop of oil on the treads of the grub screws , and insert these into the holes which are threaded in the hub , remembering that it is important not to get any oil at all onto the surfaces of the taper bush itself . Turn the grub screws loosely into place . Slide the assembly onto the shaft . Note that the bush will hold its place on the shaft where you position it , as it is being tightened . The hub will pull along the bush as you pull up the grub screw . Bear this in mind for alignment purposes .
Do not attempt to open the bush by driving a screwdriver into the split section . This will , almost without doubt , break the bush , rendering it useless . If there is difficulty in getting the bush to slide onto the shaft , this should be investigated and resolved . Be sure that all burrs have been removed . Check that you are not trying to fit an inch size taper lock onto a metric shaft , or the other way around .
In this regard , there is a possible problem between 1 inch and 25mm as the two are very close . They are however not interchangeable , 1 inch equals 25,4mm .
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RACA Journal I October 2022 47