In article .com,
wrote:
I have 2 bolts on the over arms of my Clausing 8540 Horizontal Mill. I
thought at first they were Torx T-60's but I bought one and it is too
small. It looks just like a Torx head but has about twice the amount of
teeth for the bit to go into. Anyone have any idea what type of bolt
head this is? I called Clausing and they said they did not know? I
checked the manual and no luck either. It identifies them as 1/2"-13
nuts??? Apparently Torx only goes up to a T60 so it has to be something
else. Thanks, Steve

If you are talking about a bolt with a head like the end of the
Torx wrench, not the socket, then it may be akin to what I have seen
many times on high-vacuum systems (made and sold by Varian). The bolts
were stainless steel (to survive the bakeout process without rusting),
and had a head which fit a 12-point box wrench. There was a shoulder on
the head to keep the ring of the wrench from contacting whatever was
being bolted.

The ones which I saw were smaller than yours, with 5/16" thread
being the biggest, with 1/4" being the other size, but I suspect that
such heads are available in larger sizes and other materials.

I suspect that these were not the *original* bolts on that
machine, and those would be more likely to be Allen style SCHS or even
pure hex heads.

Good Luck,
DoN.

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