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Catek Parts: Spherical Nut Dimensions


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Vote for me for the geekiest post ever:

This post is intended purely to file away in case anyone ever wants to try to machine replacements for those rare spherical nuts on Catek OS1 and OS2 bindings.  The topic has come up a couple of times before.  I don't have access to a lathe, but I do have friends in a metrology lab.  It's easy to measure the required dimensions with a caliper, except the radius of the spherical section.  So I asked a friend to measure that for me with a coordinate measuring machine.  He measured spherical radius of the nut (indicated below in red) and distance from center of sphere to flat bottom face (indicated below in blue).  The table below gives the dimensions. 



If imaging ever goes away on this forum, here are the dimensions in text:

OS1:  Radius(mm/inch) = 9.537/0.3755      Distance - Sphere Center to Face(mm/inch) = 0.782/0.0308

OS2:  Radius(mm/inch) = 12.575/0.4951    Distance - Sphere Center to Face(mm/inch) = 7.530/0.2965

This is just one measurement of one sample of each nut.  I expect pretty high uncertainty in the radius results as there's not a lot of surface to measure, plus there's significant form error.  So based on the dimensions above there's a good chance the aim radius is 0.375 inch for OS1 and 0.500 inch for OS2 (not metric - interesting).  There's probably a minus tolerance on each so they'll engage the spherical seats in the base plates which were probably made with cutters of those nominal dimensions.

Like I said, if anyone is interested, file this away for future reference.  If anyone else is a measurement geek, the CMM is a Zeiss Prismo Ultra in a 0.5 deg F room, capable way beyond the needs of this job.

Remember, vote for me for the geekiest post ever

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