Rethread the gearbox inner cover for outer cover screws

pierodn · Nov 26, 2016

Hi.
Please, i must retrhread the gearbox inner cover for the outer cover screws.
The stock screw are the n. 00.0482AK.
Is the correct size "1/4 x 26 TPI?.
Thank you
Piero

Peter R · Nov 26, 2016

Hi Piero,
1/4 x 26 tpi is correct indeed.

CanukNortonNut · Nov 26, 2016

http://www.uni-thread.com/tr_bsc_inserts.php

http://britishfasteners.com/index.php/helicoils.html

Walridge carries these special helicoils
Cheers,

Thomas
CNN

pierodn · Nov 28, 2016

Hi.
I have a 1/4 ASW tap but there is not written the TPI.
I know that 1/4 x 26 should be BSF.
There are differences from ASW and BSF?
Thanks.
Piero

L.A.B. · Nov 28, 2016

pierodn said:
I have a 1/4 ASW tap

1/4 ASW?

pierodn said:
but there is not written the TPI.

So, count how many 'threads' (cutting teeth) in one inch.

pierodn said:
I know that 1/4 x 26 should be BSF.
There are differences from ASW and BSF?

BSF has a 55 degree thread angle. 1/4 BSC/CEI (Cycle) thread is also 26 TPI but is 60 degrees.

Peter R · Nov 28, 2016

Piero, there is no such thing as ASW thread, this must be a mistake.
Buy yourself a threadgauge like this one, to find out what kind of thread you have.

Rethread the gearbox inner cover for outer cover screws

L.A.B. · Nov 28, 2016

Piero, are you sure it isn't 1/4 BSW (in which case it would be 20 TPI)?

Mike B · Nov 28, 2016

Inner cover screws are 1/4-20.
Mike B.

Peter R · Nov 28, 2016

Mike B said:
Inner cover screws are 1/4-20.
Mike B.

From Piero's post, I uderstand that his question concernes the screws that attach the outer cover to the inner cover.

DevonNorton · Nov 28, 2016

Piero

According to this list http://stainlessbits.com/link12a.html
the part number 00-0482 for outer gearbox cover screws is listed as: SCREW CEI 1/4"x26x1-1/16" SLOTTED
So the correct standard size seems to be: 1/4" diameter, 26tpi, CEI thread and 1+1/16" length. The standard is for a slotted screw.

As far as I know CEI is an earlier term practically equivalent to BSC or BScy (British Standard Cycle) thread.

Andover Norton list the part 00.0482 as SCREW 1/4"x 26TPI x1 1/16" but do not state the thread type.

So if you are keeping everything as standard then the correct size is 1/4"x 26TPI x1 1/16" using a CEI thread.
RGM list a suitable helicoil kit under Part No: 050726/BSC.

Andy

L.A.B. · Nov 28, 2016

According to John Hudson in his Norton gearbox servicing video the outer cover screws/threads are 1/4 BSF.

Rethread the gearbox inner cover for outer cover screws

pierodn

Peter R

CanukNortonNut

pierodn

L.A.B.

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