Subject: BA-Tread, The story??

From: [email-masked] (Ulf Jonsson)
Date: 6 Feb 1994 23:50:54 GMT

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! 

A friend of me had heard that it was based on an old watch makers thread.
And that they was used in car-electric system and instruments.

Can we blame LUCAS for this :-)

What is the story behind this strange system and why is it used by Stuart? 

Are they used at all today (exept in Stuarts steam engines)?

Is there a source for Hexagonal head screws with normal threads (preferably
metric) that is machined by cutting tools instead of forging-rolling so
that they look like Stuarts very beautiful screws?

Ulf

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From: [email-masked] (David Jenkins)
Date: 7 Feb 1994 09:09:54 GMT

In article <[email-masked]>,
[email-masked] (Ulf Jonsson) writes:

|> Is there a source for Hexagonal head screws with normal threads (preferably
|> metric) that is machined by cutting tools instead of forging-rolling so
|> that they look like Stuarts very beautiful screws?
|> 
|> 
|> Ulf

I can name a dozen, but they're all in the UK.  Alternatively, if you
have the technology, you can make your own.  By this I mean a lathe,
dies and some suitable hex stock.

If the lathe won't do metric threads then the dies will be good enough
for short bolts/screws, as long as the lathe is used to keep things
straight.

...presuming you have a lathe.

-- 

David Jenkins

* I'd rather be steaming... *

---

From: [email-masked]
Date: 7 Feb 94 09:45:07 PST

> that they look like Stuarts very beautiful screws?

I think what you are looking for are "Model Hex Head Bolts".
These are bolts (and nuts) with the heads cut to scale 
dimensions instead of the larger hardware store variety.

I don't know where to get metric bolts of this type.  I
just checked the Reeves (UK) catalog and they only had BA.
You can get US sizes from Power Model Supply Co. and Coles'
Power Models, Inc.  Their catalogs cost $5.00, but are 
worth it if you intend to do any amount of model building.

At P.M.S., bolts are available in single sizes and assortments
from 0-80 through 10-32, and in brass, steel and stainless
steel.   Nuts are available in both hex and square shapes.

	Power Model Supply Co.
	Route 1, Box 177
	N.W Corner of Hwy 67 and Long Rd.
	De Soto, MO 63020

	(314) 586-6466

At Coles, they do not have assortments and have only brass
and steel.   They do, however, go up to size 12-24.

	Coles' Power Models Inc.
	839 E. Front Street
	P.O. Box 788
	Ventura, CA 93001

	(805) 643-7065 (Call 9:00 AM to noon, Mon-Fri)

--  Alan E. Frisbie               [email-masked]
--  Flying Disk Systems, Inc.
--  4759 Round Top Drive          (213) 256-2575 (voice)
--  Los Angeles, CA 90065         (213) 258-3585 (FAX)

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From: [email-masked] (Panther)
Date: Mon, 07 Feb 1994 13:58:24 +0000

In article <[email-masked]>,
[email-masked] (Ulf Jonsson) wrote:

> I found a table over BA-Threads in a handbook. To me the system looks like
> some funny logarithmic scaled system based on BA-0 wich have metric

> Are they used at all today (exept in Stuarts steam engines)?

The BA system is based on a Swiss system of instrument maker's threads and
was adopted for small instrument work after an extended study by the
British Association around the turn of the century.  It is so well liked in

the UK that it has resisted displacement by metric threads and is likely to
remain in force for many years.  I would be surpised if it were not widely 
known in the US also.  Commercial screwing tackle, nuts, bolts, etc, are
available here from commercial outlets at reasonable prices.

The system is indeed based on a geometric series for all its major
dimensions,
with a scaledown of, I think, 0.9 per unit, so 1BA is 0.9mm pitch, 2BA is
0.81 mm pitch, etc.  It is specified down to 16BA (try getting that in
metric!)
but only the even numbers are commonly used, which has spoilt the
flexibility
of the system somewhat.

I appreciate some of this is a bit vague - its from memory - and I could
post more details if anyone is interested, but to be honest, I thought you
would all know about it.  Mail me if you're interested (or even to tell me
that no-one in the U.S. knows about it!)

Clive W.