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So the headsteady bolts are 5/16-22 which is Whitworth, if I understand this correctly. Do most people leave them so or retap for 5/16-24 SAE? Or even better a helicoil or if it was practical, a Timesert?
Headsteady Bolts
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So the headsteady bolts are 5/16-22 which is Whitworth, if I understand this correctly. Do most people leave them so or retap for 5/16-24 SAE? Or even better a helicoil or if it was practical, a Timesert?
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swooshdave said:
They're actually 5/16 BSF (British Standard Fine).
As a 5/16 "Whitworth" (British Standard Whitworth = BSW/W) thread would be 18 tpi.
http://www.britishfasteners.com/threads/bsf.html
http://www.britishfasteners.com/threads/bsw.html
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L.A.B. said:
I was questioning Whitworth when I wrote it but had forgot about the BSF. Why on earth if the carbs could be UNC they would make the headsteady BSF?
So, the question is, leave it or change it? I ask because I don't have the BSF bolts and would just as soon retap.
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pvisseriii said:Please correct me if I'm wrong but those three bolts should be the last that you tighten before the tank goes on. When all is lined up, adjusted and straight them snug them to specs and all should be well for the test ride next week.
If it was only so. Besides I still have to MAKE the headsteady! :mrgreen:
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swooshdave said:
I think maybe you could be approaching this from slightly the wrong angle?
As BSW, BSF, BSCy, BA, BSP, etc. threads were used on British motorcycles long before the rather too late and therefore somewhat unnecessary partial (in the case of Nortons) change over to Unified threads.
Some Unified threaded parts were introduced at the start of Commando production, and then for 1971, more BSW/BSCy parts were replaced with Unified, however the change-over to Unified threads didn't appear to progress much further than that, so it was never completed. Maybe they didn't get around the changing the head bracket threads over to Unified, or maybe the factory considered the equivalent "two-pitches-suits-everything" UNF/UNC threads were not as suitable for the application as the good old 22 tpi BSF?
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L.A.B. said:
Yeah, I'm sure they were thinking that it would all be better if they just went back to a dead standard. :mrgreen:
Take it easy with this one. This is where fine thread in alloy is risky. I can't for the life of me understand why they used fine instead of coarse here. The headsteady has some load to support. If anything I would oversize and re-tap for UNC. I have also snapped a bolt off that had corrosion frozen in. If you are using a later model box headsteady, the centre bolt location is pain to fit, so I find it easier to use a hex head and not an Allen screw as you can fit a ratchet socket onto the hex head, where as the Allen key fouls under the lower frame rail.
Mick
Mick
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I have a spare Mk III headsteady (no spring, frame tube bracket or adjusted bolt) that you can have for shipping if you want it.swooshdave said:pvisseriii said:Please correct me if I'm wrong but those three bolts should be the last that you tighten before the tank goes on. When all is lined up, adjusted and straight them snug them to specs and all should be well for the test ride next week.
If it was only so. Besides I still have to MAKE the headsteady! :mrgreen:
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swooshdave said:
Like the Unified thread standard is now, you mean?
I think it was simply a waste of time and resources for the Norton factory to partially adopt a thread standard (Unified) that was already in the process of being phased out.
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L.A.B. said:
Some places in the world are still holding on to it. Probably those places that have resisted Metric to the bitter end. :mrgreen:
Pretty sure books have been written about the ill-advised decisions in the British motorcycle industry at the time. No need to pile on now.
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Danno said:I have a spare Mk III headsteady (no spring, frame tube bracket or adjusted bolt) that you can have for shipping if you want it.swooshdave said:pvisseriii said:Please correct me if I'm wrong but those three bolts should be the last that you tighten before the tank goes on. When all is lined up, adjusted and straight them snug them to specs and all should be well for the test ride next week.
If it was only so. Besides I still have to MAKE the headsteady! :mrgreen:
Thank you very much for the offer. I'm still hankering to make one of these:
So far the aluminum is going to cost me $20 and the rod ends another $20. So I'll be in it about $50. At least that's the theory.
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