Front Fork Tapped Holes for what?

jaydee75 · May 12, 2013

Down in front of the axle on both fork legs there is about a 5/16 tapped hole that I have never seen used. Could some of you old timers please tell me what they are (were) used for? I have seen this on both old and newer Nortons.
Thanks,
Jaydee

madass140 · May 12, 2013

is it similar to the one behind the axle?

L.A.B. · May 12, 2013

jaydee75 said:
Down in front of the axle on both fork legs there is about a 5/16 tapped hole that I have never seen used. Could some of you old timers please tell me what they are (were) used for? I have seen this on both old and newer Nortons.

Pre-MkIII models usually have two front mudguard stays, so four mounting points are required.

With the forks reversed on the MkIII models a front stay could not be fitted with the caliper ahead of the fork leg unless the front section of the mudguard was extended. [Edit] It was also becoming the fashion of the period to fit only the one stay, and later still, none at all.

jaydee75 · May 12, 2013

OK, thanks.
I can thread a 5/16-18 UNC in, but it is a little loose. I suppose it is a British thread. What is it?
Thanks in advance.
Jaydee

L.A.B. · May 13, 2013

jaydee75 said:
I can thread a 5/16-18 UNC in, but it is a little loose. I suppose it is a British thread. What is it?

It is UNC. (Same part number all Commando, 060357).

http://www.nortonmotors.de/ANIL/Norton% ... e-list.php

060357 HEX. SCREW 5/16"UNC x 1/2"

Rohan · May 13, 2013

It can only be 5/16" UNC or Whitworth.

In theory it should be UNC, but with Nortons you never know....

Throber · May 13, 2013

It was probably put there as a cost cutting exercise

B+Bogus · May 14, 2013

Throber said:
It was probably put there as a cost cutting exercise

Probably correct in a perverse way - imagine the cost of changing the drawings and castings. Definitely easier to carry on as before.

Very British

Yes, I'm a British Engineer, and I've seen it more often than I'd care to mention :roll:

Throber · May 14, 2013

B+Bogus.
Thank god !
Someone who get's it. An intelligent person with a working brain.
And a sense of humour.

Bernhard · May 16, 2013

BTW;
If the thread was ¼ Whitworth, it is exactly the same as ¼ UNC ‘
Once you get to the Commandos, depending which year it was made, some had, UNC , UNF, Whitworth, BSF and cycle thread fittings all on the same
bike :!:

L.A.B. · May 16, 2013

Bernhard said:
If the thread was ¼ Whitworth, it is exactly the same as ¼ UNC

Actually Whitworth and UNC threads are not exactly the same.

Bernhard said:
Once you get to the Commandos, depending which year it was made, some had, UNC , UNF, Whitworth, BSF and cycle thread fittings all on the same bike :!:

All years of Commando have that mixture of threads (plus a few others, BSP, BA, etc.) although there are more Unified fasteners on the later models.

B+Bogus · May 16, 2013

L.A.B. said:
Bernhard said:

If the thread was ¼ Whitworth, it is exactly the same as ¼ UNC

Click to expand...

Actually Whitworth and UNC threads are not exactly the same.

Quite so, and almost impossible to tell the difference as the pitch is the same, but the flank angle is 55 degrees for Whitworth, as opposed to 60 degrees for UNC.
Some highly respected aftermarket manufacturers will happily mix them, but it doesn't appeal to me much! :roll:
I believe early Commandos were Whitworth & Cycle thread, and they changed over in the late 60's to UNC/UNF, but I'm not totally sure - possibly when the points were relocated to the timing case?

L.A.B. · May 16, 2013

B+Bogus said:
I believe early Commandos were Whitworth & Cycle thread, and they changed over in the late 60's to UNC/UNF, but I'm not totally sure - possibly when the points were relocated to the timing case?

You won't find many Commandos that weren't built in the late 60's :wink: (or later). Commandos certainly had many Unified threads from the start of production.

B+Bogus · May 16, 2013

L.A.B. said:
You won't find many Commandos that weren't built in the late 60's :wink: (or later). Commandos certainly had many Unified threads from the start of production.

Indeed!

Just had a quick browse of the parts lists and it looks like the '68 crankcase was still BSW/BSC (Atlas - type cases?) - by '69 it was all UNF/UNC.
I wonder if the gearbox ever went over? I suspect not. Why change an 'established' design? :?

Just realised how 'trainspotter' it's all getting!
Where's me anorak? :roll:

L.A.B. · May 16, 2013

B+Bogus said:
Indeed! Just had a quick browse of the parts lists and it looks like the '68 crankcase was still BSW/BSC (Atlas - type cases?) - by '69 it was all UNF/UNC.

Cylinder base studs changed to Unified for 1972, but various British Standard fasteners lasted until the end of Commando production (cylinder head, head steady, rocker feed, etc.)

B+Bogus said:
I wonder if the gearbox ever went over? I suspect not. Why change an 'established' design? :?

Just realised how 'trainspotter' it's all getting!
Where's me anorak? :roll:

Gearbox fasteners didn't change so remained British Standard (BSF etc.)

Front Fork Tapped Holes for what?

jaydee75

madass140

L.A.B.

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jaydee75

L.A.B.

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Rohan

Throber

B+Bogus

Throber

Bernhard

L.A.B.

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B+Bogus

L.A.B.

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B+Bogus

L.A.B.

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