Re: {Collins} Dial setscrew tool

I've tried grinding the ends of Bristol and Allen wrenches to a SLIGHT dome or cone shape. They self-center in the screw, then drop right into place when you rotate them. Of course, you don't want to overdo this or you'll reduce the spline engagement.


On 12/4/2012 12:55 PM, Roy Morgan wrote:

On Dec 4, 2012, at 12:28 PM, Keith Carlsen wrote:

Great links, which we appreciate.


Glad to help when I  can.

But here's a question I have not heard: Why are Bristol Spline fasteners so uncommon

Replaced by Torx drivers and hardware. I suspect these can be made by automatic machines more easily and cheaply than the sharp-edged Bristol splines. The Bristol configuration is rather precision compared to the Torx, and as a result of the radially-oriented driving force surfaces has greater strength.

(A few strokes from your sharp-cornered fine sharpening stone will make a new Bristol wrench find its home in the screw very nicely.)

Much of American hardware and equipment is built for ease/economy of manufacture and low or moderately demanding applications. Our automobiles used to be made with nuts and bolts, now they are welded, or use drive-in fasteners, or even GLUED together. I used to have a '69 Volvo and marveled at the ease with which everything went together. And the Volvo was nothing compared to a Rolls of the same era! A machinist once showed me his small set of British made metric taps. They were like jewels! If we made stuff like that in the US, our industries would go out of business even faster.

We can do it right though. I have a main transmission bolt from a helicopter I once flew (H-34 - there were *only three bolts* that held the whole thin in the air), and I can assure you it has a very smooth finish, has very fine, perfect threads, and is worthy of trusting your life to its strength and function. (We did.)

and why do so few tool vendors sell them?

Not enough profit.

The Snap-On guy never even HEARD of them

Ignorant. And he's in the TOOL business! (I think that Snap-On actually does have Bristol drivers, but I can assure you that you really would not want to pay their prices!)

and my brother the A&P mechanic/avionics tech said they are "used in weird old stuff".

I kinda think he's right.  Carry on enjoying your "Weird Old Stuff"!


Roy Morgan
K1LKY Since 1958 - Keep 'em Glowing!


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