View Full Version : 5C hex/square blocks, is there a reference chart? (sort of inscribed circle)

05-24-2012, 10:37 PM
So I was machining a piece of 3/4" hr steel today, and decided a hex on the end would be good so I could put a wrench on it to screw it in (it has one end turned down and threaded to 5/8-11). Out comes the hex 5C block.

That's when the question came up.. What standard wrench size hex head can I machine on a 3/4" dia. rod?

Is there a reference chart somewhere for this? Am I missing something stupid simple? :)

05-24-2012, 10:46 PM
Copywrite issue removed.

E (max) = D x 0.866 = 0.75 x 0.866 = 0.6495" accross hex (max).

Any hex with an accross the flats not exceding 0.6495" ( ie 5/8" = 0.625" A/F).

05-24-2012, 10:51 PM
My "Machinist's Ready Reference", the "Engineers Black Book", probably "Machinery's Handbook" and no doubt most others will have a page labeled Distance Across Corners of Squares and Hexagons. So the across corners dimension of your stock is the circumscribed circle of your hexagon. The books say if the distance across corners is 3/4 is .7576 then the distance across flats will be 21/32" so that the largest wrench you could use. Probably the most sense would be 5/8" if you don't have the 21/32 wrench as I don't.

05-25-2012, 08:33 AM
If it is a piece of 3/4 square stock, you're missing either an adjustable wrench or an eight point socket....unless your really want to mill a fancy end on it.;)

05-25-2012, 10:48 AM
Thanks guys.

Found it on page 80 of the Machinery's Handbook (#28). It has the formula, as well as a table for common fractions. Just what the doctor ordered.

Once I knew what I was looking for (distance across corners), it was easy to find.

Oh, and it's round stock. :)

05-25-2012, 12:31 PM
then drill a hole through it and make it a "T handle" with the addition of a cross piece. You'll not need a wrench or socket again...;) or just mill a couple of wrench flats on it.