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Whitworth in chrome
- Thread starter Hobot
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Its perhaps also worth pointing out that the bolt head sizes on modern ''whitworth' bolts are waaay smaller than on the original whitworth bolts - which had quite large/longer heads.
So would look totally wrong on an older bike that actually used whitworth fasteners.....
So would look totally wrong on an older bike that actually used whitworth fasteners.....
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The head sizes on Whitworth (BSW) bolts are usually based on the smaller BSF head sizes, even though they have the same shank diameter, and it would be unusual to find the older larger BSW head on a piece of machinery if it was built after the second world war, so most of our classic machines would not look odd with the smaller headed bolts or nuts. I know this stuff because I used to machine all sorts of weird threads for the chemical industry.
And I agree it does sound scary when the company is going to send UNC bolts instead of BSW, they won't fit! :shock:
And I agree it does sound scary when the company is going to send UNC bolts instead of BSW, they won't fit! :shock:
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pvisseriii said:
I must admit I don't understand what you mean or what it is you're actually asking?
What is supposed to be "goofy"(?) or somehow "ass backwards"?
Answers in plain English if possible for us Brits (OK, for me then) please?
I was under the impression that all the bsw threads on the Norton were 26 tpi whether they are 1/4, 5/16, 3/8, 1/2 and so on. I know of course that there are many other type of fasteners, but I am talk about anything that takes a Whitworth wrench. That is wear my confusion stems from.
I have one Whitworth wrench, for the 1/4 for that tricky spot on the back of the cylinder base. For everything else 6 point metric or inch does the trick. I have done without that wrench for quite some time but finally decided on the convienence. But I degress.....This is about fasteners.
Instead of having standard inch wrenches for BSC stuff, they have Whitworth head with for inch (UNF/UNC) stuff.
I have one Whitworth wrench, for the 1/4 for that tricky spot on the back of the cylinder base. For everything else 6 point metric or inch does the trick. I have done without that wrench for quite some time but finally decided on the convienence. But I degress.....This is about fasteners.
Instead of having standard inch wrenches for BSC stuff, they have Whitworth head with for inch (UNF/UNC) stuff.
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pvisseriii said:
Ah, I see, but no, it's CEI/BSC "Cycle" thread that is often 26 TPI, not Whitworth.
http://www.britishfasteners.com/threads/bsw.html
http://www.britishfasteners.com/threads/bsc.html
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The real concern is a vendor selling 'equivalent' fasteners which patently are not.
They'll no doubt screw in (to the alloy) OK, but once torqued down things will never be the same again :roll:
Not sure if a thread pitch gauge would highlight the crime either, unless under magnification.
They'll no doubt screw in (to the alloy) OK, but once torqued down things will never be the same again :roll:
Not sure if a thread pitch gauge would highlight the crime either, unless under magnification.
The real question here maybe should be - are there any whitworth threads on a Commando anyway ??
The timing cover screws are maybe the only possibility, along with the mudguard stay bolts (into the alloy fork sliders). Or are they UNC thread form ? Anyone know ?
I've got older Nortons, and the only whitworth threads anywhere on them is the timing cover screws - and UNC stainless go quite nicely into them, although they feel a shade looser until you tighten them up.
Prewar bikes that did really use whitworth threads would only be correct if they used the larger nut and bolt head sizes, as mentioned. The size reduction was supposedly to save metal during WW2.
P.S. Have seen that 'whitworth' is loosely used to describe any british threadform, so maybe this is yet another example... ?
The timing cover screws are maybe the only possibility, along with the mudguard stay bolts (into the alloy fork sliders). Or are they UNC thread form ? Anyone know ?
I've got older Nortons, and the only whitworth threads anywhere on them is the timing cover screws - and UNC stainless go quite nicely into them, although they feel a shade looser until you tighten them up.
Prewar bikes that did really use whitworth threads would only be correct if they used the larger nut and bolt head sizes, as mentioned. The size reduction was supposedly to save metal during WW2.
P.S. Have seen that 'whitworth' is loosely used to describe any british threadform, so maybe this is yet another example... ?
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This is turning into an interesting 'thread' 
The UNC and BSW threads do have the same TPI in some of the diameters, but they are different, not only in a five degree included angle but also the UNC/UNF have a flat top to the thread apex, something to do with the ability to hold a lubricant better, and the BSW/BSF are full form threads with a radiussed apex. If you want to screw a dissimilar nut and bolt together, don't be surprised when the thread gets ripped out or distorted, due to lack of face contact.
A thread gauge will show the difference in angle and also the flat or radiussed top, just hold up to a strong light source (not the Sun tho' !!! :shock: )
The UNC and BSW threads do have the same TPI in some of the diameters, but they are different, not only in a five degree included angle but also the UNC/UNF have a flat top to the thread apex, something to do with the ability to hold a lubricant better, and the BSW/BSF are full form threads with a radiussed apex. If you want to screw a dissimilar nut and bolt together, don't be surprised when the thread gets ripped out or distorted, due to lack of face contact.A thread gauge will show the difference in angle and also the flat or radiussed top, just hold up to a strong light source (not the Sun tho' !!! :shock: )
+1, good point or ah.. radius?Cheshire bloke said:
The Machinery's Handbook notes this rounding of the peaks and valleys (inside and outside threads vary in their profiles) is primarily to accommodate wear on threading tools during manufacture. I also remember reading that this radius in the valley adds strength (possibly similar to the way the pto shafts on a Norton crank benefit from a radius at the join).
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