whats the purpose of dual hex nuts

[James]

what’s the purpose of dual hex nuts used all over on my 63 Scott? They had to be a pain to manufacture

[Geoff Case]

Hi James Some one, years ago, told me the nuts you inquire about were , EX WD stock, bought cheap after the last war. Sounds about right to me!

[James]

Neat story,thanks.Why would the military need such a nut? And me finding them on my Scott is a good sign as it has the original (quirky) hardware, in a Whitworth hex head/thread form. BTW the shock bolts are too short to thread all the way through the nuts but I think they are what was used originally . I’m in the process of removing the hardware piece by piece and plating it as the nuts and bolts were just covered with silver paint. Now don’t tell me that was the way they were supposed to be! 😆

[chris wastell]

If the nuts were ex War Dept I expect they would be zinc plated at most.

[chstorm]

Scott used double nuts for a long time, especially for fastening the engine to the frame. One nut is the fastener, the second nut is a lock nut to avoid that vibration loosens the fastener. Works fine. Today’s solution would probably be a nyloc nut or Loctite 242.
On my bikes, some nuts were missing, and I made new in stainless steel from a 1″ hexagon bar. Took some time, but the result was nice.

Carl

[James]

these are not two nuts, they are one nut with two different hexes. No locking effect. I’ll get some before and after photos of the plating work.

@chstorm wrote:

Scott used double nuts for a long time, especially for fastening the engine to the frame. One nut is the fastener, the second nut is a lock nut to avoid that vibration loosens the fastener. Works fine. Today’s solution would probably be a nyloc nut or Loctite 242.
On my bikes, some nuts were missing, and I made new in stainless steel from a 1″ hexagon bar. Took some time, but the result was nice.

Carl

[Stan Thomas]

I researched the origin of these nuts (which were only one size – 3/8 BSF) with a major fastener (nuts to you) manufacturer, and apparently they were for an R.A.F contract after the WW2 – but how Matt got them (other than out of a skip) remains a mystery…….

You have a choice regarding why they are bi-hexagonal, as the boffins (even those not domiciled near Nottigham) cannot agree as to whether it was to save material or effect some measure of “torque-up control” out in the colonies.

No wonder the ‘planes I maintained during National Service kept crashing.

[James]

heres a before plating photo of the bihex nut

[James]

Also looking for a 5/16 BSF nut like this one in steel, it is the passenger peg pivot bolt nut.

[Tony Kitching]

I don’t know about dual hex nuts, but with regard to lock nuts I was taught that the lock nut went on first and the full nut next. after fully tightening, the lock nut was backed off a fraction to pass the load onto the full nut. could it be that the dual hex nuts were used in order to cut down on the amount of tools needed to carry out emergency repairs. Just a thought.
Tony Kitching

[dave bushell]

My ’48 Scott, when I acquired it in the early ’50s, was fitted with 16 dual hex nuts on the cylinder head.
Dave

[James]

@dave bushell wrote:

My ’48 Scott, when I acquired it in the early ’50s, was fitted with 16 dual hex nuts on the cylinder head.
Dave

Wow !

[BRIAN MARSHALL]

According to my son, recently retired RAF Chief Technician (Airframe), the idea behind these nuts was that you tightened them into place using the smaller of the two hexagons, and loosened them using the larger hexagon, the idea being that you were less likely to overtighten them when using a smaller, shorter spanner. Bear in mind that this was a half-baked theory for the days when nobody out ‘in the field’ had heard of a torque wrench ! The idea fails dismally of course because the two different hexagons were probably on opposite ends of the same spanner, so exactly the same amount of leverage could be applied. When in use on an aircraft there was also a slight weight-saving consideration, and the cost of making them would be of little consideration. Many fasteners on an aircraft are in very awkward to access positions, and no doubt having two different hexagons also offered the opportunity to use different tool sizes when in a tight corner…
Now you know.
Brian

[BigKev]

Thanks Brian for your last post. Now I will be able to sleep at night. Kevin.

[BRIAN MARSHALL]

Sweet dreams Kev….
Brian

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