18mm ring!

Yes, and then again, no, dear.

A 7/8" bolt head would be gripped on all six sides, but anything smaller
would be in contact with two fixed flats and the two flats on the
sdjustable slider, innit. Four flats out of six in contact.

Still wouldn't like to use it, mind - tool of last resort, the slipping
spanner.

 

Yersh. My (not serious) point was they say it grabs on *all* 4 sides,
not 4 of the 6 sides.

 

Wha'? Coach bolts have a rounded head with a little square section
immediately underneath on the shank, pshirley?
http://en.wikipedia.org/wiki/Screw

Their nuts may be square IIR our old farm sleds C...
(Not always: http://www.toolstation.com/shop/p74965 ...)

One square-head amongst a raft of domed heads in google images:
http://nbcnybc.en.made-in-china.com/product/TojmbvpEgIki/China-Coach-Bolt-017-.html

--
Ivan Reid, School of Engineering & Design, _____________ CMS Collaboration,
Brunel University. Ivan.Reid@[brunel.ac.uk|cern.ch] Room 40-1-B12, CERN
GSX600F, RG250WD "You Porsche. Me pass!" DoD #484 JKLO#003, 005
WP7# 3000 LC Unit #2368 (tinlc) UKMC#00009 BOTAFOT#16 UKRMMA#7 (Hon)
KotPT -- "for stupidity above and beyond the call of duty".

 

Traditionally maybe, but I've got a bunch of big self-tapping square
head coach bolts. They're great for screwing beams together if you
haven't got one big enough for the job.

 

Umm, no, those are coach *screws*, a totally different beast.

http://www.fastfixdirect.co.uk/code/navigation.asp?fType=fasteners&MainCategoryID=6

(Kidza! Don't they know the difference between a screw and a bolt?)

--
Ivan Reid, School of Engineering & Design, _____________ CMS Collaboration,
Brunel University. Ivan.Reid@[brunel.ac.uk|cern.ch] Room 40-1-B12, CERN
GSX600F, RG250WD "You Porsche. Me pass!" DoD #484 JKLO#003, 005
WP7# 3000 LC Unit #2368 (tinlc) UKMC#00009 BOTAFOT#16 UKRMMA#7 (Hon)
KotPT -- "for stupidity above and beyond the call of duty".