Subject: Re: BA-Tread, The story??

From: [email-masked] (Peter Northway)
Date: Thu, 10 Feb 94 19:24:46 +1300

In <[email-masked]> [email-masked] (Ulf Jonsson) writes:
>I found a table over BA-Treads in a handbook. To me the system looks like
>some funny logaritmic scaled system based on BA-0 wich have metric
>dimensions. (I think BA-0 have 6mm dia and 1mm pitch).

>The diameters and the pitch for the other threads in the serie is not eaven
>in either decimal or fractional inces or in SI units. And the profile is
>has 47.2 degree angle instead of 55 or 60! 

Stuff deleted.

Reference 1: Model Engineers Handbook - Tubal Cain

	"The Pitch of each BA thread is 0.9 X the pitch of the next larger
	size rounded off to the nearest 0.01mm. The daiameter of a BA screw
	is given by D=6P^1.2 ".

Reference 2: Fowler's Mechanics and Machinists Pocket Book 1941

	"British Institution Standard Thread. - A standard for small screws,
	such as are used by opticians and in telegraphic work, has been
	adopted on the report of a committee of the British Institution. 
	The thread has an angle of 47 1/2 deg., and is rounded off top and
	bottom with a radius two-elevenths of the pitch." 

	there then follows two tables, one marked "British Institution
	Standard Thread" and a much more comprehensive table entitled
	"B.A. Threads". The dimensions in both tables are identical.

This may not answer your query but I thought it might be of interest.

-- 
     Peter Northway        | Disclaimer : This is just my opinion. Well more
  Wanganui New Zealand     | like a tiny ripple in the fabric of the universe.
[email-masked] | Well would you believe just another beer break.

---

From: [email-masked] (John Kopf, X6305)
Date: 10 Feb 94 20:13:34 GMT

In article [email-masked], [email-masked] (David Jenkins) writes:
> <stuff deleted>
> have the technology, you can make your own.  By this I mean a lathe,
> dies and some suitable hex stock.
		^^^^^^^^^^^^^^^^^^

if you only need to make a small number of some special size, Allan wrenches
are hex, cheap, and come in all sizes...use them for stock.

(And, while we're at it, an Allan-head bolt can be turned down, screwed into
a piece of aluminum bar - for a handle - and made into a dandy nut-driver for
those odd size bolts and nuts.)

JK