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On my belt sander, there is a small cast aluminum drive pulley/wheel about 1.25" diameter that slips over a 5/16" shaft. Two flats on the shaft mate with two flats inside the bore. The internal flats in the bore have sheared off, so now the wheel just spins on the shaft instead of driving it.

The manufacturer no longer makes the cast aluminum wheel, and no parts stores via google have any old stock left.

I have two ideas for fixing it 1) mill keyways (too expensive) or 2) drill a hole for a 'shear pin' (spring pin, roll pin; which is my plan at the moment). I'm open to other suggestions.

For the pin, what is the optimum diameter and what metal? If it is small, it'll likely shear under normal use. If it is large, then the shaft will be weakened too much.

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  • $\begingroup$ the diameter has to be proportional to the force applied and the thickness of the available materials : there are suggested sizes for this type of pin - but I can't lay my hand on them at the moment... $\endgroup$ – Solar Mike Oct 19 '17 at 5:58
  • $\begingroup$ Its a 110v 5A motor. $\endgroup$ – mike Oct 19 '17 at 6:28
  • $\begingroup$ Is it feasible to use thermal release Loctite to bond the pulley to the shaft? Then you can avoid any machining. $\endgroup$ – user6335 Oct 19 '17 at 8:26
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    $\begingroup$ Please add photo of the pulley. $\endgroup$ – GisMofx Oct 20 '17 at 13:03
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One other possibility is to mount the motor / pulley in a drill stand and drill a "keyway" axially between the shaft and pulley then put a pin in that hole - 2mm dia but 10mm long which would work well...

You may have to do the first pass with a similar metal to the shaft : a nut and then drill again with the pulley as the drill may wonder off as the pulley is soft in comparison...

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  • $\begingroup$ This method of keying is apparently called a "Scotch Key". But the term seems to be archaic and seldom used. The method is sound though, it is most often used for "in the field" repairs because all you need is a drill and a hammer. $\endgroup$ – user6335 Nov 20 '17 at 8:14
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you can also try mixing some 5 minute epoxy with fine metal dust as a filler/thickener, to yield a heavy paste, and then apply enough of it to the shaft to fill the gaps between it and the bore.

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