Archive for February, 2012

I am looking… for a very Particular (Peculiar) Fastener

February 11, 2012

I am looking – and looking – and looking… Can’t find it to save my life…

So, what’s this fastener Brian is obsessing about? Well, this is a mechanical engineering problem to solve with two requirements:

1) I need to capture a 1/8″ diameter rod securely in the vertical plane – it will be under a great deal of stress from vertical forces in both the upward and downard directions;

2) This rod needs to pivot in the horizontal plane about one end between the corners of two overlapping horizontal metal plates that hold the ends of the rod’s fastener.

I need a fastener most commonly called a “barrel nut”. Here is a drawing of one (dimensions in inches):

I can cut a 4-40 thread on one end of the rod and screw the barrel nut onto the rod, and drill a 3/16 hole through corners of the two plates. It will work fine! If – if I can ever find my barrel nuts…

I have learned a lot about barrel nuts. They are also called:

Cylinder nuts, or
Sex nuts, or
Joint connector nuts.

In the furniture industry, barrel nuts precisely twice as large as what I need in every dimension with a slot on one face for adjustment are commonly available called:

Futon nuts, or

Barrel nuts are commonly used in the airplane industry to fasten the wings to the fuselage – they must be enormous barrel nuts!

In the automotive, motorcycle and bicycle industry where there are wire cables and ropes used to pull levers on the carb, transmission or brakes, a similar fastener is applied at the end of the cable. This similar fastener has a smooth hole where the barrel nut has a threaded hole – for the cable to pass through, and it has a threaded hole running through the pin between the round faces for a set screw to secure the cable. I can use these fasteners, too – I just finish the end of my 1/8″ rod a bit differently – if I can only find what I need. Moped cable hardware (they are smallest) look highly promising! These particular fasteners are called:

Cable stops, or
Knarps (uniquely in the bicycle industry – pronounced KahNARPS).

In the marine industry (for boats), a barrel nut has a very different form that is simply a threaded sleeve with a head on one end. Not what I need at all…

In the firearms industry, a barrel nut has another different form due to its purpose to attach the barrel of a gun to the gun frame. Also not what I need…

So many names for the same form of fastener, and so many fasteners of the same name but with different forms makes searching online exceeding difficult and frustrating. This is a very specialized fastener with no standard sizes except for the case of the futon nuts where there are actually two common sizes available.

I can fashion something close to what I need from a 3/16″ diameter clevis pin. I can cut a 4-40 thread in the cotter pin hole and cut the pin to length, but one end of the barrel nut will be rather short and may not be retained securely. I’ll try, though, and see how well that works.

I can order exactly what I need from China in massive quantities delivered to my door in a few weeks – for 2.6¢ each in quantities of 100,000 or more (or 500Kg depending on the factory).

I have learned quite a lot about barrel nuts!

You see – I actually have one of these barrel nuts in my hand – right this moment – just like the drawing above – made from stainless steel – I need these made from 303 stainless steel (forgot to mention…). But I need six of these buggers. If anyone knows where I can purchase exactly what I am looking for, please LET ME KNOW!

––––––––  An Update ––––––––

The steel guitar industry uses this barrel nut in the lever and peddle assemblies that control that instrument’s features. I must say that a steel guitar turns out to be a remarkably complicated instrument! Well, Steel Guitars of Canada came to my rescue with a few of their valuable pieces of hardware mailed discretely from Colborne, Ontario without charge.  My THANKS go out to AL for his generosity! I think that Al at Steel Guitars of Canada is a super fellow. If you are in the market, visit his website.

Thanks – Brian