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PAW 55 crank thread?

Old 11-07-2009, 10:13 AM
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soarrich
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Default PAW 55 crank thread?

Hello
What is the thread on the crankshaft of the PAW 55?
Thanks
Rich Border
USA
Old 11-07-2009, 09:14 PM
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gkamysz
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Default RE: PAW 55 crank thread?

I'm 99% sure it's a 4BA. That sucks because I have a 55 that runs fine but has a slightly injured crank thread. I can get props on and have run it, but I'd like to fix it. The 4BA is a wonderful 3.6mm major diameter and .66mm pitch. If it's true BA then, the angle is not the common 60°. So unless you get a BA tap or die you're pretty much out of luck.

Greg
Old 11-07-2009, 11:02 PM
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soarrich
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Default RE: PAW 55 crank thread?

4BA is what most agree it is. I'm going to make a nut that goes into the TF Power prop's .210 hole so that I can run them with a spinner. With a spinner there's not enough thread sticking out past the prop to hold it on.
Old 11-08-2009, 01:54 AM
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Default RE: PAW 55 crank thread?


ORIGINAL: gkamysz

I'm 99% sure it's a 4BA. That sucks because I have a 55 that runs fine but has a slightly injured crank thread. I can get props on and have run it, but I'd like to fix it. The 4BA is a wonderful 3.6mm major diameter and .66mm pitch. If it's true BA then, the angle is not the common 60°. So unless you get a BA tap or die you're pretty much out of luck.

Greg
The angle for BA series screw threads is 47.5 degrees IIRC. However 4 BA split dies arn't hard to come by. My local supplier has them for aud 12.65, slightly over $10 US.

See http://www.ejwinter.com.au/catalogue/ejw-tools-8-08.pdf

They are probably also available much closer to home.

Ray
Old 11-08-2009, 09:12 AM
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Default RE: PAW 55 crank thread?

Finally got a responce to my emails to PAW, so straight from the horse's mouth.

Hi

The thread is 4BA.

Kind regards
Paul Eifflaender

Progress Aero Works
Tel/fax +44 (0)1625 423891
[email protected]
www.paw.ac

Union Mill
Union Street
Macclesfield
Cheshire
SK11 6QG
United Kingdom
Old 11-08-2009, 11:54 AM
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Default RE: PAW 55 crank thread?

BA tooling is a bit harder to find in The Colonies. It's useless when your lathe can't cut the thread and nobody uses the series.
Old 11-08-2009, 04:05 PM
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Default RE: PAW 55 crank thread?

ORIGINAL: gkamysz

BA tooling is a bit harder to find in The Colonies. It's useless when your lathe can't cut the thread and nobody uses the series.
Correct, the treads per inches for BA treads are not in use in mostly of all lathes. See this link: http://homepages.tesco.net/~A10bsa/bago.htm

It will be possible to set up required treading size by change gear if the change gear set are calculated by lead screw and treads per inches at bolt/screw.
The BA4 has 38,5 TPI, the change gear set up will be driven gears 40x90 driver gears 25x30 and will give TPI 38,4, it is not much wrong and will go in the treads at 38,5, the error are 0,259% (Max error acceptable are 1%). The lathe has 8 TPI.

Except some Myford lathe has the equipment to make BA treads, it has a Norton change box who can make BA treads.

The other solvent are to buy the treading set with BA tap and die, but the tap and die will be unused in the tool room in a lot of years..[]
Old 11-08-2009, 04:29 PM
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Default RE: PAW 55 crank thread?

ORIGINAL: gkamysz

BA tooling is a bit harder to find in The Colonies. It's useless when your lathe can't cut the thread and nobody uses the series.
Ah yes but US citizens are still allowed to buy 4 BA Dies by mail from the rest of the empire. The BA series was also used extensively in the screws in the electrical systems of British cars and bikes. You may find a local classic restorer who has one

Alternatively how about I send you a 4 BA die and you in return send me $10? If this is a solution PM me your address

Ray
Old 11-08-2009, 05:54 PM
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Default RE: PAW 55 crank thread?

Right, Jens. I figured I would just pick a thread as close a possible that my lathe will actually cut. The extent of the damage is a few threads. $10 for something I will use for 15 seconds ends up very expensive. That's why the repair has been on the back burner for a few years. That and I didn't bother to check to see what the thread actually was until the topic came up.
Old 11-08-2009, 08:37 PM
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Default RE: PAW 55 crank thread?


ORIGINAL: gkamysz

$10 for something I will use for 15 seconds ends up very expensive.

A new crank is 26 pounds plus shipping, so you looking at $40.

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