BSC thread nightmare

Information relating to the Matchless G2 or AJS Model 14 250cc Lightweight
ade
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BSC thread nightmare

Post by ade »

In preparation of assembling my M14 I thought I would purchase the most common thread tap/dies. Is BSC going to be the most likely thread do you think? I cannot find a BSC thread gauge for sale anywhere including Ebay! Anyone know what my crankcases and cylinder bolts are likely to be?

Hang on, does BSC fall into the whitworth category?
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Janet
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Re: BSC thread nightmare

Post by Janet »

They also use BSF and BA.
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alanengineer
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Re: BSC thread nightmare

Post by alanengineer »

BSC is a 60 deg thread form. If you are looking for a pitch gauge, a Whitworth one will do in combination with a micrometer
oldandsmelly
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Re: BSC thread nightmare

Post by oldandsmelly »

I would get yourself a table of thread sizes. There are a few good ones free on the net that you can download. I keep a print copy in with my taps and dies cos now matter how often I use them I can't remember all the specific details.

BScy is normally 26 threads per inch (TPI) for most encountered stud sizes. A good set of imperial / whitworth thread guages will include 26 TPI. To double check, I always measure the stud diameter as well and check in the thread tables for good measure.

This probably isn't the best place for recommendations, but I get most of my taps and dies from Tracy Tools. Not always the cheapest but top quality. If you are only going to be rescuing or cutting new threads in aluminium then carbon steel is fine. If you may be making many threads into steel, then HSS is better but quite a lot more expensive. Second hand cycle thread taps and dies also sometimes turn up on ebay.
ade
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Re: BSC thread nightmare

Post by ade »

Thanks Oldandsmelly, Allenengineer forgive my ignorance but how does that work with a whitworth gauge in 55° and a micrometer?
JEAN-NOEL
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Re: BSC thread nightmare

Post by JEAN-NOEL »

I agree with Oldansmelly about Tracy Tools. I think that with several taps you could do most of the job : for my G12's restoration i used only
- 1/4 X 20 TPI (BSW) for studs screwed in aluminium castings
- 1/4 X 26 TPI Cycle
- 5/16 X 26 TPI Cycle.
If you want only to clear (refresh) your threads, only the third tap (finisher) is necessary.
SPRIDDLER
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Re: BSC thread nightmare

Post by SPRIDDLER »

You of the cognoscenti shame me. :oops:
I am a Philistine. (I know my place).

I have plenty of time and a biscuit tin full of recycled 'handy' nuts, and an OXO tin with about 50 anonymous pre-loved taps, bought at random and for pennies at autojumbles and stalls at boot fairs and country shows.

When I need to clean up threads in ali I proceed like the old lady who swallowed a fly:

I take out the stud that's in the ali.
I find a nut that fits the stud.
I find a tap that fits the nut.
And use the nut to clean the threads.
Having little or no idea what thread it is.
'There is a tide in the affairs of men
Which taken at the flood............'
JohnHewes
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Re: BSC thread nightmare

Post by JohnHewes »

Spriddler, I thought you knew better!
Some things are not very important and I often do like you and don't worry about the minute detail. (If it's goes well, most of the oil stays inside and I still have lights when I get home then I am a happy chappy).
But on this question I like to be sure that I have the thread identified and I use a thread gauge and a chart and a vernier to confirm what I have before I cut metal.
You can never tell whether a previous owner has used, say, a 10mm bolt in place of a 3/8" one and it is easy to waste a threaded hole in aluminium particularly.
Also get decent sharp taps and dies, I use old ones too if I don't have the correct one, but don't do as I do!
ade
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Re: BSC thread nightmare

Post by ade »

Such wonderful advice from you all. Why is it impossible to find a Nylock 5/16 BSC nuts?
oldandsmelly
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Re: BSC thread nightmare

Post by oldandsmelly »

Try Stig Fasteners, they list a selection of nyloc BSCy nuts including 5/16.

Hopefully, this link will take you there if my fat fingers have copied the link OK:

http://www.a2stainless.co.uk/British-St ... B234V.aspx
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