# Square Head to Hex Head?



## Dwight Ennis (Jan 2, 2008)

Does anyone know when the transition took place from square-headed bolts and square nuts to hex-headed bolts and hex nuts? I'm reasonably sure it was after the turn of the 20th century.


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## JEFF RUNGE (Jan 2, 2008)

Dwight, look like you are correct,  but I did come across the name Whitworth and the year 1841 in several searches.  But no references to a patent or the like. There was indication that some clock  and gun makes may have been the first, circa 1850's


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## Mike Reilley (Jan 2, 2008)

My grandfather was the general manager of a US Steel nail and screw factory. Square headed nuts were also called cut nuts. Cut nuts were made by drilling/punching a large sheet of steel with thousands of holes aligned in rows and columns. ... Then the sheet was "cut" in a shear to create long "stick" of steel with a single row of holes. These long pieces were fed into another machine that threaded the holes...then a smaller shear cut across the "stick". The cutting process wasn't very accurate...and that's why cut nuts didn't always have the hole in the center of the nut.

The bolts were made from steel "wire". The wire was heated till it was soft...then put into a machine that squashed the head area to form a mushroom like head...and it also cut the bolt to length. The bolts were then pushed through a form that squared the head. This resulted in some of the heads being distorted and not centered on the wire shaft. The next step rolled the threads onto the wire shaft.

For both bolts and nuts, heat treating/hardening of the metal was the last step. 

By the way...that 1949 agreement to standardize nuts and bolts into ISO inch and ISO metric was probably when the square headed bolts/nuts ended production in mass...as it would have required new investments in machinery.


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## Del Tapparo (Jan 4, 2008)

That's very interesting Mike. I remember all of the oddities of shapes and alignment. It now makes sense.


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## armorsmith (Jun 1, 2008)

Mike, 

Thanks for the history lesson, very informative. 

Bob C.


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## Dwight Ennis (Jan 2, 2008)

That's very interesting Mikey, thanks. Similar methods of manufacture were probably used prior to mechanization, though on a smaller scale and with manually operated machinery. Sounds a lot like the info on the link posted on FB about how carriage bolts were made.
It's intriguing that, for such a common thing as bolts and nuts, so little about their history is readily available on the web.

BTW, I posted the same question on the NorCal Group. Randy Hees responded with the following...

*The primary driving force was use of socket wrenches. Generally square heads are better for open end "hand" wrenches.

Generally we see square head bolts used on the Carter built equipment, but, we do find some hex on passenger cars, suggesting that hex was higher class. Similarly we find hex used earlier on air brake equipment, when installed on a wood car built with square head bolts. I suspect a locomotive or similar machine used more hex earlier as well.

Our West Side flat cars (built 1928-1928) have a mix of square head and hex...

As late as 1995 square head bolts were easily available at local specialty shops in a great variety of lengths and sizes (for example, 2, 7/8x17", the bolts were made to order, with a 2 week lead time). At the time there were two head sizes for any bolt diameter, a normal, and "heavy head"

Today, I am able to get nuts (but there are sizes that are difficult) and some shorter bolts. The special order option is more challenging...

Square head bolts were standard for line pole work until recently, and square nuts are still standard (required by building code in some cases) for concrete foundation work where they will be tightened up by hand wrenches.*


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## SteveC (Jan 2, 2008)

Maybe you'll find these of interest.

Bolt, Nut, and Rivet Forging (1914) - Chapter I Heading Machines[/b]

American Railway Master Mechanics' Association (1899)
Pages 238 - 272[/b]

Wikipedia - Screw Thread / History of Standardziation[/b]

Sizes - Screw Thread Series[/b] 

Sizes - When is a Bolt a Screw?[/b]


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## Don Howard (Jan 2, 2008)

Here's a red hot site: 


Belgian site 


The pictures are worth 1000 words.







Anybody have a source for 1:20.3 square nuts?



Or bolts?


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## Bluestem Lady (Jan 6, 2008)

Hello! 

I came across this thread and didn't know if Don ever found the square nuts and bolts. My hubby restores antique motorcycles and I had to find some about four years ago for a delivery box/van on a 1930 Harley. I finally found what we needed at a blacksmith supply site http://www.blacksmithsdepot.com/Tem...eLocation=/Resources/Products/hardware&where= 

It lists several sizes, quality was very good and so was the price (I thought). Mind you, these are black nuts and bolts. 

Hope you will be able to find what you need. Even if they don't have it, the site is really interesting. 

Cindy


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