G.S. Case "Stresses on Bolts: Nut Dimensions: Wrench Design" 1926
G.S. Case "Stresses on Bolts: Nut Dimensions: Wrench Design" 1926
(OP)
thread404-262508: Obtaining Old Reference - Torque Capacity Hex Features
thread404-200026: Hex torque strength
Hi,
Both of the above threads reference G.S. Case "Stresses on Bolts: Nut Dimensions: Wrench Design" (1926), specifically with regard to the following formula, for calculating rounding of a hex feature:
TH = CH · WAF2 · WR.H · UTS · NC
where
TH is the hex torque capacity
CH is a constant (=0.103)
WAF is the width across flats
WR.H is the wrenching height
UTS is the ultimate tensile strength
NC is the number of pairs of driving contacts (NC = 3 for a hexagon
(Credit to CoryPad on the original thread).
I've been trying to get hold of that reference. I've checked Google Scholar, my University's online library, the Institution of Mechanical Engineers online library, and even Amazon (long shot). I can't find it - other than 3 citations found on Google Scholar.
Does anyone know where I can get hold of a copy of this?
In the same vein; this is an old reference (1926) - has anyone seen any more up to date literature for calculating at what torque an internal hex drive will fail?
Thanks in advance.
thread404-200026: Hex torque strength
Hi,
Both of the above threads reference G.S. Case "Stresses on Bolts: Nut Dimensions: Wrench Design" (1926), specifically with regard to the following formula, for calculating rounding of a hex feature:
TH = CH · WAF2 · WR.H · UTS · NC
where
TH is the hex torque capacity
CH is a constant (=0.103)
WAF is the width across flats
WR.H is the wrenching height
UTS is the ultimate tensile strength
NC is the number of pairs of driving contacts (NC = 3 for a hexagon
(Credit to CoryPad on the original thread).
I've been trying to get hold of that reference. I've checked Google Scholar, my University's online library, the Institution of Mechanical Engineers online library, and even Amazon (long shot). I can't find it - other than 3 citations found on Google Scholar.
Does anyone know where I can get hold of a copy of this?
In the same vein; this is an old reference (1926) - has anyone seen any more up to date literature for calculating at what torque an internal hex drive will fail?
Thanks in advance.





RE: G.S. Case "Stresses on Bolts: Nut Dimensions: Wrench Design" 1926
RE: G.S. Case "Stresses on Bolts: Nut Dimensions: Wrench Design" 1926
That's an interesting note about allowing drive tools to 'pop' through the flats; no doubt Titanium combined with a pan head design would make this even more likely.
RE: G.S. Case "Stresses on Bolts: Nut Dimensions: Wrench Design" 1926
Or, are you really designing or evaluating a fastener ?
RE: G.S. Case "Stresses on Bolts: Nut Dimensions: Wrench Design" 1926
I work for a company in orthopaedic medical devices. For clarity, I also study part time for my degree. This is for work though.
I have hand calculations for every other aspect of the screw (and associated assembly). I haven't been able to track down any calculations for rounding out a hex so far, I'm hoping that this reference has some answers or at least a direction to follow.
RE: G.S. Case "Stresses on Bolts: Nut Dimensions: Wrench Design" 1926
I had an open end wrench that measured a little larger than all my other wrenches, so I ran some improvised tests with a good dial torque meter. (Yes, I am insane.) There was no mistaking it, the few thousandths of an inch of extra room made a big difference.
RE: G.S. Case "Stresses on Bolts: Nut Dimensions: Wrench Design" 1926
http://www.jegs.com/images/photos/800/868/868-4918...
Is the installation torque greater than the torque for a conventional hex head cap screw with your hex size?
Will you have some control over What installation tools are going to be used ?
I can't imagine the hex being the weak link unless it is quite puny compared to the thread size.
Kind of the opposite of this -
https://d6u22qyv3ngwz.cloudfront.net/ad/7TFM/audi-...
RE: G.S. Case "Stresses on Bolts: Nut Dimensions: Wrench Design" 1926
= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube
RE: G.S. Case "Stresses on Bolts: Nut Dimensions: Wrench Design" 1926