Thread types
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Thread types
Hi guys, this may sound like a silly question but what threads were used on the mid 40s bikes, I have ben told BSF and BCY,(BSC) similar threads but slightly different cut. I need to purchase a few taps that cost a small fortune for each and would like to order the correct ones. Any help greatly appreciated.
Thanks , Steve.
Thanks , Steve.
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Re: Thread types
BSF is generally used for threads and studs going into alloy castings and BSC (British Cycle) for frame/cycle parts. I would say that Whitworth thread is the most common on our old bikes. It's common the a stud will have BSF on the end that goes into say an alloy crankcase but Whitworth at the other end for a nut. BA threads are also found - mainly on electrical equipment (dynamos, switches plus the end cover plates on the singles oil pump) but it's unlikely they'll ever need to be tapped out on electrical equipment .
Shame you're not in the U.K. as loads are available cheaply at autojumbles.
This info in the 'Tech Articles' section will help you.
https://www.jampot.com/article_read.asp?id=391
Shame you're not in the U.K. as loads are available cheaply at autojumbles.
This info in the 'Tech Articles' section will help you.
https://www.jampot.com/article_read.asp?id=391
'There is a tide in the affairs of men
Which taken at the flood............'
Which taken at the flood............'
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Re: Thread types
Thanks for your reply , it sounds like I may need a bit of everything but at least i know now what to start collecting if and when I do come across them.
Thanks again for advise, as usual invaluable.
Cheers, Steve.
Thanks again for advise, as usual invaluable.
Cheers, Steve.
- Pharisee
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Re: Thread types
Tracy Tools stock just about every tap you can imagine and their delivery is excellent. If you're only buying taps to clean out existing threads, you don't necessarily need expensive HSS ones. A cheaper carbon steel tap will do.
I'm from the Fens.... Gimme six.
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Re: Thread types
+1 for that.
Their 'loose sets' of two taps per size, plus die, in BSF, BSW, BSC, BA etc, at £20 a pop in the sizes we need, are pretty OK. I've used them for ages, saving a bit of hard-earned for HSS kit in sizes I need regularly for cutting fresh threads.
https://www.tracytools.com/product-cate ... -and-dies/
Because they come loose, no wasted weight or postage cost on packaging or tools either.
- Joker_Bones
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Re: Thread types
Is that the case for '40s bikes? All the bikes I have worked on are '50s and '60s but I can't think of any Whitworth threads on them.
As you say... BSF into ally but, with a few exceptions, the remainder have been BSC.
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Re: Thread types
You've got me thinking now, JB. I mostly use Whit spanners and sockets on the engines and gearboxes of my ex '47 Ajay and current '54 Matchless.Joker_Bones wrote: ↑Wed Feb 21, 2024 4:43 pm Is that the case for '40s bikes? All the bikes I have worked on are '50s and '60s but I can't think of any Whitworth threads on them.
As you say... BSF into ally but, with a few exceptions, the remainder have been BSC.
TBH I just pick up the spanner that I habitually use for that particular job without looking at what it is marked and without giving a thought to the thread form of the fixing. I've always assumed, perhaps naively, that a fixing requiring a Whit size spanner has a Whit thread form.
'There is a tide in the affairs of men
Which taken at the flood............'
Which taken at the flood............'
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Re: Thread types
Ha! Thinking can be a risky biz Neville. But - the thought's not essentially wrong.
Whitform (hybrid sort of word) about covers it, as BSF and BSW (and I think one or two other thread forms maybe) come under that heading. Just a Q of tpi, but all 55°as opposed to other thread angles, and I'm sure there's stuff on roots and crests and all that good stuff too.
BSF was developed to provide heavier / stronger core diameter than the coarser original 'whitworth' offered, and I guess more contact area between bolt 'n 'ole/nut.
Same spanners fit Cycle nuts and bolts too of course . . .
So, there's loads of whitform on our machines, and loads of 60° BSC at 26tpi, some at the alternative 20tpi in larger sizes, and there's BA at 47 'n a 'arf. Most of the whitform as we might now call it is BSF - but some fasteners into aluminium are in fact BSW. Studs with 1/4 x 20 tpi (BSW) one end and 1/4 x 26 t'other (60° BSC or could be 55° BSF to the naked eye just to confuse) aren't rare on AMC stuff (and are common on a lot of other marques).
In terms of tap and die usage on 'our' bikes, BSF and BSC are the main men, but a few BSW things may be handy, and a bit 'o BA for the 'leccy side as you said originally (also, for Twin owners, for timing cover screws, at a ridiculous 2BA into ally - no wonder so many timing side crankcases have trouble there).
Whitform (hybrid sort of word) about covers it, as BSF and BSW (and I think one or two other thread forms maybe) come under that heading. Just a Q of tpi, but all 55°as opposed to other thread angles, and I'm sure there's stuff on roots and crests and all that good stuff too.
BSF was developed to provide heavier / stronger core diameter than the coarser original 'whitworth' offered, and I guess more contact area between bolt 'n 'ole/nut.
Same spanners fit Cycle nuts and bolts too of course . . .
So, there's loads of whitform on our machines, and loads of 60° BSC at 26tpi, some at the alternative 20tpi in larger sizes, and there's BA at 47 'n a 'arf. Most of the whitform as we might now call it is BSF - but some fasteners into aluminium are in fact BSW. Studs with 1/4 x 20 tpi (BSW) one end and 1/4 x 26 t'other (60° BSC or could be 55° BSF to the naked eye just to confuse) aren't rare on AMC stuff (and are common on a lot of other marques).
In terms of tap and die usage on 'our' bikes, BSF and BSC are the main men, but a few BSW things may be handy, and a bit 'o BA for the 'leccy side as you said originally (also, for Twin owners, for timing cover screws, at a ridiculous 2BA into ally - no wonder so many timing side crankcases have trouble there).
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Re: Thread types
Thanks Bill. Thinking about it (for the first time in 60 fettling years), I'm pretty sure I use a Whit spanner on my single's rocker cover bolts which have a 5/16" BSF thread form.
'There is a tide in the affairs of men
Which taken at the flood............'
Which taken at the flood............'
- Joker_Bones
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Re: Thread types
And... British Standard Pipe (BSP) on the oil and petrol fixtures and fittings.