According to :
I got a tool & cutter grinder head from a junk shop (for free) that is
missing the arbor nuts and outer collars.The bearings are in good shape
as well as the motor itself.

But I can't find the arbor nuts.

I've measured the shaft and threads but I can't decide if they measu
16 mm x 1.25 mm
or
5/8" by 20

I suspect that either one wouold work after a fashion since neither
seems to be an exact match for the thread pitch.

Hmm ... while you're at it -- check the handedness of the
threads. The nut on my Sanford small surface grinder is a left-hand
thread. And it has no flats. it is a disc, with a bit of relief so the
contact with the wheel is only near the OD.

And the outside surface has two shallow holes for using a pin
spanner to tighten the nut.

However, my regular sources for odd size stuff (www.boltdepot.com and
www.fastenal.com) don't list either one of these sizes.

It seems a shame to toss the work head just because I can't locate a
couple of arbor nuts.

Any ideas?

Once you are sure as to what the thread is, consider making your
own nut on your lathe. (I presume that you do have a lathe, if you are
posting here about a T&C grinder. :-) 5/8" should be possible to thread
internally with a proper internal threading tool. Much smaller and it
gets tricky. :-)

Good Luck
DoN.
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