Hexagonal Socket Drive

[Mike DonnerstagParticipant @mikedonnerstag]

[Mike DonnerstagParticipant @mikedonnerstag]

I have a ratchet wrench and brace with a 7/16" hexagonal drive, instead of the (more modern I assume) square drive. Does anyone still use these? Anyone know what they were for and what vintage they are and, more to the point, whether they're worth anything to anyone?

The ratchet wrench is a Britool 2073.

Many thanks,

Mike

Edited By Mike Donnerstag on 06/06/2019 12:42:45

[Michael GilliganParticipant @michaelgilligan61133]

A quick search on Google shows plenty of these for sale … You are not likely to get rich.

Hex drive sockets were once fairly common, but were made obsolete by 'market forces'

… rather like Betamax VCRs

MichaelG.

[Kenneth DeightonParticipant @kennethdeighton43272]

In my apprenticeship days we still used the hexagon type socket sets , the advantage of them was the sockets being much slimmer than the square drive ones and you could get them into smaller gaps etc.

Ken.

[Nick HulmeParticipant @nickhulme30114]

Posted by Kenneth Deighton on 06/06/2019 19:36:50:

In my apprenticeship days we still used the hexagon type socket sets , the advantage of them was the sockets being much slimmer than the square drive ones and you could get them into smaller gaps etc.

Ken.

That will be because a hex is smaller than a square then? 😀

[Mike DonnerstagParticipant @mikedonnerstag]

Great – thanks chaps.

Mike

[Howard LewisParticipant @howardlewis46836]

The Britool; 7/16 hexagon drive socket sets were good quality, and quite durable. They predate WW 2

My father bought his when he started a garage in the thirties. We used it into the early 60s. I borrowed it and used it to earn my first money repairing cars in the late 50s.. I inherited it and only needed to replace one socket, (in the late 60s ) and used until the mid seventies.

Last year, I donated it to The WaterWorks Museum for their "Old Workshop" to be cherished, although still a quite useable item.

Howard

[SillyOldDufferModerator @sillyoldduffer]

I can't find a reference to confirm it, but I think, weight-for-weight, that a square section bolt head is stronger (less likely to deform and slip) – than a hexagon head. They're also easier to make. I associate square heads with heavy engineering.

The advantage of a hexagon head is it can be approached from more angles with a spanner. This extra accessibility is highly desirable in a system of general purpose fasteners.

On a socket-set I suspect a hex drive adds to the cost of both driver and sockets to little advantage. Ease of manufacture and strength won the day – customers don't like paying for features they don't need.

The maths needed to compare wings vs triangular vs square vs hex vs polygonal heads is beyond me. (I just tried!) Can anyone confirm square is stronger than hex or am I typing rubbish again?

Dave

[clogsParticipant @clogs]

I have a couple of extension bars from who knows where….

they make great drifts…u can pound on them all day….hahaha…..

more old crxp from our distant past…..

a bit like flat head wood screws…..

just thrown a load of them in the bin (20kgs)…..

onwards and upwards….hahaha……

[Michael GilliganParticipant @michaelgilligan61133]

Posted by SillyOldDuffer on 07/06/2019 08:56:07:

I can't find a reference to confirm it, but I think, weight-for-weight, that …

The maths needed to compare wings vs triangular vs square vs hex vs polygonal heads is beyond me. (I just tried!) Can anyone confirm square is stronger than hex or am I typing rubbish again?

.

Regarding torsional stiffness: Have a look at 'polar moment of inertia'

[your CAD package may have such calculations inbuilt]

But the matter of slippage, and rounding of corners, has a lot to do with tolerancing.

MichaelG.

[not done it yetParticipant @notdoneityet]

One end of a modern day socket is hexagon (or more likely 12 pointed) and the other end is driven by a square drive. So go figure! Heavy duty sockets (impact air tools) are always hexagon.

Hex was easier to access from cramped angles without having too many corners to round over. Sqare bolts and nuts were originally forged by the simple smithy, so afforded dimensional accuracy without too much trouble.

So I doubt it was a purely structural engineering decision to adopt the hexagon shape.

Sockets with 12 points are clearly adequate when used on hex fixings in most instances.

Virtually all really old ploughs and other farm machinery have square headed fixings.

The problem with access to square fixings would have been very much been removed (had they been retained) by the invention of the ratchet in the socket set.

Allen keys were introduced and now we have torx, too. Screw heads were slotted, then cross point (in various guises) and now in a multitude of forms, but the Canadians (and US?) still retain the Robertson square drive screws. So I reckon it was just ease of use that caused the change to hex from square. Likely the same for sockets – we all know which is the driver end and which is to fit the nut!

[Alistair Robertson 1Participant @alistairrobertson1]

I remember when I bought my first Britool socket set in mid to late sixties I was offered either square or hex socket sets. I went for the square because there were AF sockets in the set (There were only Whitworth in the hex drive set although some of them were 8 sided for square nuts!

My Uncle who owned the garage where I got to use the ramp etc. bought the hex set. I think it was a lot cheaper than the square one (He was always tight with his money!) and was probably old, old stock.

When he retired and sold out I looked for the Hex set but I never found it and he could remember nothing about it!

[Robert Atkinson 2Participant @robertatkinson2]

I wonder if it has anything to do with IP? Snap on used square but don't seem to have patented that
**LINK**

Maybe someone in the UK had a patent on square drive?

[Clive FosterParticipant @clivefoster55965]

Slight topic drift but reading through Robetts Snap On link I saw :-

"The Weidenhoff Corporation of Algona, IA was acquired in 1956. This brought the manufacture of automotive test equipment into the Snap-on line. Voltmeters, Ammeters, Distributor and Alternator Testers and the Anal-O-Scope"

?? For cars!! ??

The last being somewhat unfortunate branding. Even by American standards where insertion of -O- in the middle or i on the front seems to be an irremovable national trait.

Clive

[Guy LambParticipant @guylamb68056]

Some sets of sockets at the cheaper end of the scale had an Allen key instead of a ratchet, the set I have is also Whitworth.

Guy

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Michael Gilligan on 07/06/2019 10:38:47:

Posted by SillyOldDuffer on 07/06/2019 08:56:07:

I can't find a reference to confirm it, but I think, weight-for-weight, that …

The maths needed to compare wings vs triangular vs square vs hex vs polygonal heads is beyond me. (I just tried!) Can anyone confirm square is stronger than hex or am I typing rubbish again?

.

Regarding torsional stiffness: Have a look at 'polar moment of inertia'

[your CAD package may have such calculations inbuilt]

But the matter of slippage, and rounding of corners, has a lot to do with tolerancing.

MichaelG.

.

Dave,

I must confess to being mildly disappointed that we have not yet seen the first release of:

'Duffer's illustrated guide to the Torsional Stiffness of DriveShafts with various Sections'

MichaelG.

[SillyOldDufferModerator @sillyoldduffer]

Posted by Michael Gilligan on 08/06/2019 14:33:59:

Posted by Michael Gilligan on 07/06/2019 10:38:47:

Posted by SillyOldDuffer on 07/06/2019 08:56:07:

I can't find a reference to confirm it, but I think, weight-for-weight, that …

The maths needed to compare wings vs triangular vs square vs hex vs polygonal heads is beyond me. (I just tried!) Can anyone confirm square is stronger than hex or am I typing rubbish again?

.

Regarding torsional stiffness: Have a look at 'polar moment of inertia'

[your CAD package may have such calculations inbuilt]

But the matter of slippage, and rounding of corners, has a lot to do with tolerancing.

MichaelG.

.

Dave,

I must confess to being mildly disappointed that we have not yet seen the first release of:

'Duffer's illustrated guide to the Torsional Stiffness of DriveShafts with various Sections'

MichaelG.

It's that Joe Noci's fault, he's got me mainlining on an ST Nucleo Microcontroller F446RE.

However, I can offer this first step:

Observations:

1. The square head has about 15% more metal in it, and is presumably stronger
2. The bearing surface available to the spanner on a hex head is 56% of that available on a square head. A square bolt would experience less pressure on its faces for the same turning force, which I suppose is less likely to chew the head up.
3. The extra strength of a square head compared with a hex head may be irrelevant because in both cases the diameter of the bolt's shank is the identical weak point.

My feeling is that hex heads are convenient because more faces are available, but a square bolt should resist wear and tear better. In both cases a properly fitting ring spanner would spread the turning forces better than the ordinary type by using all the faces rather than only two. Also possible that square performs 'better' than hex with an ordinary spanner, but hex is better than square if a ring spanner or socket is used.

Might mock up a few heads in modelling clay and see if it's obvious which shape is more easily deformed. Otherwise, I've got torsional analysis in CAD on my to-do list…

Dave

[Clive FosterParticipant @clivefoster55965]

interesting analysis but the resistance to rounding off issue has more to do with goodness of fit between the nut and spanner than raw geometry. Obviously the spanner has to have a certain clearance between itself and the nut so it can be put on. Once the clearance is taken up the force will be concentrated on a relatively small bearing area close to the tip. The slacker the spanner the smaller the bearing area and the more readily the nut will round off.

Nightmare calculation especially when considering 12 point ring on a hex head. Presumably a graph of slackness v strength could be plotted but you'd need to take into account the actual material properties as the shear line will be on some sort of diagonal below the corner. Classic example of that are the modern bolts with surface hardened heads due to the cold forming process. Very strong if the hex is undamaged but far weaker if its anything more than little imperfect.

Flank drive was developed as a response to that problem. Theoretically pushing onto the flanks gives a lot more metal to resist torque as the loads aren't concentrated at the tips of the hex or square.

In a practical world both hex and square can be made strong enough but hex is better for access as giving 6 bites per turn rather than 4. More with correctly offset spanner heads. 12 point ring for same more bites reason as offset open ended spanners. 12 point carried over into socket but not so needful if you have a strong ratchet. Still handy with a breaker bar tho'.

Clive

[Michael GilliganParticipant @michaelgilligan61133]

Thanks, Dave … 'though I must admit that's not quite the direction in which I was trying to point you.

Clive has rightly picked-up on the tolerancing aspect … which of course ultimately leads us away from 12-point sockets, and on to 'flank drive' configurations for sockets.

However: Your first self-imposed calculation was [or so I thought] going to be to compare the torsional stiffness of bars of different shape cross-section, but the same 'weight per unit length' of material.

That said … whatever you do is sure to be interesting.

MichaelG.

[SillyOldDufferModerator @sillyoldduffer]

Posted by Michael Gilligan on 08/06/2019 17:30:48:

Thanks, Dave … 'though I must admit that's not quite the direction in which I was trying to point you.

Clive has rightly picked-up on the tolerancing aspect … which of course ultimately leads us away from 12-point sockets, and on to 'flank drive' configurations for sockets.

However: Your first self-imposed calculation was [or so I thought] going to be to compare the torsional stiffness of bars of different shape cross-section, but the same 'weight per unit length' of material.

That said … whatever you do is sure to be interesting.

MichaelG.

Not ignoring your suggestion Michael, in fact I think it will be very revealing. More the size of the queue and a concern about my ability to get CAD working quickly! I was able to do the comparison in about 10 minutes.

Clive's comments are relevant too. Now he's pointed out all spanners must have point contact rather than tightly fit the flanks, it's obvious my observations are off-beam. Have to see what can be done about simulating tight and loose fitting spanners.

Making my head hurt. I expect a clever bloke sorted it all out around 1850!

Dave

[Michael GilliganParticipant @michaelgilligan61133]

No rush at all, Dave

We know you're on the case …

MichaelG.

[Clive FosterParticipant @clivefoster55965]

Dave

Its not point contact but the load area can be pretty small. Essentially hex and spanner distort until there is enough contact area and shear line area back to the main body of the head to carry the load.

Depends on the way the head is made where the shear happens. Ordinary homogeneous hexes usually swell as part of the shear process giving more contact area often enough to get it off one last time if galled or corroded on.

Those modern hard faced due to cold forming thingies don't deform much. usually just wipe the whole corner off. The cheapie integrated washer and tapered hex ones being the worst. I want a quiet work with the guy (or gal) who thought they were a good idea!

As for figuring out whats going on thats a job for hybrid analogue – digital computer. Digital to set the basic parameters. Analogue to run the graphs out just like that and ensure you don't hit garbage in garbage out.

Clive

[SillyOldDufferModerator @sillyoldduffer]

Another interim report – I found FreeCAD's FEM Workbench has been updated significantly since I last used it, and took a while to get anywhere. Pretty sure I'm not doing it right! Finite Element Method is the application of a 'Finite Element Analysis', more detail about the theory on Wikipedia.

Anyway, in FreeCAD's Part Design Workbench I sketched a 20mm square and extruded it by 100mm to create a solid 3D body. Then I drew a crude spanner outline on one end, and extruded that. I made a number of cuts in the 'spanner' so that it only makes contact with the square rod in realistic places, thanks Clive. (Cuts are made by sketching rectangles and applying the pocket tool.)

Once the rod and spanner combination existed, I switched to the FEM Workplace and:

• created a Solver
• Defined the Solid Material as Aluminium 6061-T6 (only because it happens to be the first metal listed in the database.) The database defines the properties of many common materials: Density, Young's Modulus, Poisson Ratio, and Thermal Properties, or you can enter your own. These measures are used by the Solver to calculate bending, strength and other structural behaviours.
• Added a 'mesh' to the model. The computer fills the model with small triangles. These are used by the solver to break the analysis into manageable chunks. By solving stress in one triangle, the results can be applied to it's neighbours until the whole object is solved. Note the computer doesn't look up the formula for a bending a beam and apply that, rather it generalises the problem so that any shape can be solved. The finer the mesh the more accurate the result. As there's a huge amount of complicated number crunching, a computer is essential. Too much work for humans, and tedious.

• Added a fixed constraint to the far end of the square rod. This is equivalent to clamping it in a vice.
• Added a sideways force to the end of the spanner handle such that the rod will try to rotate. As the other end is constrained, the rod will twist. How much will the rod twist, what will break first, and which parts are over-strong?

At this point the Solver has enough information about the object to perform an analysis. Here's the whole Model as listed in the 'Combo View':

Double clicking the Solver 'CalculiXccxtTools' line opens a dialogue. Clicking the 'Write .inp File' button saves the specification and a 'Run' button appears. Pressing this adds the CalculiX_static_results entry, and the Results_mesh. Double Clicking 'CalculiX_static_results' opens another dialogue that can be used to select various displays, in this example X-displacement:

The min, avg, and Max numbers aren't correct because I messed with the model but the colour map correctly shows the spanner in tension and compression on opposite sides and also that the rod is twisting, mostly at the top and not at all at the bottom. Hardly surprising, I drew a weedy spanner and a hefty rod.

Not worked out how to tabulate results. There are a lot of other features I haven't explored and I don't properly understand the ones I've got working either! Dynamic forces can be analysed, also heat, fluid flow in a pipe, and something to do with electrostatics. No ideas what the new set of tools for post-processing results do!

I can't answer the original square vs hex head question, but how it might be done with FEM is taking shape.

I've also found that Machinery's Handbook has a couple of pages on shafting of various shapes. There are formula for all the common shapes. A mathematician might 'see' which, if any, are stronger just by looking at the formula. Not me, I'd have to feed them all with numbers and compare the results. Another nice job for a computer!

More if I get the time. Too many diversions.

Dave

Edited By SillyOldDuffer on 10/06/2019 17:34:22

[Nigel McBurney 1Participant @nigelmcburney1]

ok the theorys nice but could the real reason for going to hex drive commercial in that if you had say a set of whit sockets and the various drivers eg t bar ratchet,various extensions, when you needed extra some a/f or metric sockets you had to buy Britool sockets as other makers square drive would not fit your drivers. A friend who had a business reconditioning motor components many years ago had a Brittool hex drive set, they survived many years continuously used for stripping Bed ford steering boxes, they were nice to use and bit lighter than the king dick /elora square drives.

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