BSW threads

[David Tinsley]

1955 A10 GF

I am looking at getting some BSW taps and dies. First job is to make extended studs for the new sump plate with drain plug I am going to fit.
I am trying to decide whether to buy a kit, or individual taps and dies. I know i need 1/4" BSW for the sump studs and I think a 3/8" might be worth getting as well?
Are there any other sizes that are in common use on this bike? If I need more than two sizes I might as well spring for a set, but dont want to have items in there that will never see the light of day.
Cheers,
Dave

[chaterlea25]

Hi Dave,
1/4 and  5/16 Whit  only on the A10
Can't think of a 3/8 unless you have a Trihard
You will need 1/4 , 5/16 and  3/8 x 26 for the fine cycle threads
1/4 BSF is also 26tpi and does the same job

John

[David Tinsley]

Hi Dave,
1/4 and  5/16 Whit  only on the A10
Can't think of a 3/8 unless you have a Trihard
You will need 1/4 , 5/16 and  3/8 x 26 for the fine cycle threads
1/4 BSF is also 26tpi and does the same job

John

Thank you John,
I will buy just those two sizes then. I already have a full set of CEI so OK there.
Cheers,
Dave

[muskrat]

G'day DT.
3/8"BSF for the head bolts/holes. Always handy to have a couple of thread files, 1 metric and 1 imperial.
https://tinyurl.com/yansm698  https://tinyurl.com/ect6yaz7
Cheers

[David Tinsley]

G'day DT.
3/8"BSF for the head bolts/holes. Always handy to have a couple of thread files, 1 metric and 1 imperial.
https://tinyurl.com/yansm698  https://tinyurl.com/ect6yaz7
Cheers

I have never got around to getting thread files, but I know I should! Tend to use dies for cleaning up threads. And thread files are not cheap, unlike me 

[KiwiGF]

Hi Dave,
1/4 and  5/16 Whit  only on the A10
Can't think of a 3/8 unless you have a Trihard
You will need 1/4 , 5/16 and  3/8 x 26 for the fine cycle threads
1/4 BSF is also 26tpi and does the same job

John

Thank you John,
I will buy just those two sizes then. I already have a full set of CEI so OK there.
Cheers,
Dave

UNC is close to Whitworth, just thread angle is different, and tpi on 1/2”.

[David Tinsley]

Hi Dave,
1/4 and  5/16 Whit  only on the A10
Can't think of a 3/8 unless you have a Trihard
You will need 1/4 , 5/16 and  3/8 x 26 for the fine cycle threads
1/4 BSF is also 26tpi and does the same job

John

Thank you John,
I will buy just those two sizes then. I already have a full set of CEI so OK there.
Cheers,
Dave

UNC is close to Whitworth, just thread angle is different, and tpi on 1/2”.

My understanding is that the difference in the thread angle between BSW and UNC is enough to make them not really interchangeable? Is my understanding wrong? Would make life simpler if I can use UNC instead of Whitworth. But, I dont want to bugger things up either!

[Rex]

BSW is readily available, so why use UNC which isn't an exact alternative?

[KiwiGF]

Hi Dave,
1/4 and  5/16 Whit  only on the A10
Can't think of a 3/8 unless you have a Trihard
You will need 1/4 , 5/16 and  3/8 x 26 for the fine cycle threads
1/4 BSF is also 26tpi and does the same job

John

Thank you John,
I will buy just those two sizes then. I already have a full set of CEI so OK there.
Cheers,
Dave

UNC is close to Whitworth, just thread angle is different, and tpi on 1/2”.

My understanding is that the difference in the thread angle between BSW and UNC is enough to make them not really interchangeable? Is my understanding wrong? Would make life simpler if I can use UNC instead of Whitworth. But, I dont want to bugger things up either!

I would not use a UNC tap or die on any important whitworth thread eg case but I would use a UNC bolt or nut on a BSW thread (not a stud hole) if it fitted well enough, at least the head size is in inches (AF). UNC is more available and you are more likely to have a nut or bolt knocking about in a tin somewhere.

Heaven forbid if I have not got a CEI nut and bolt for (say) a mudguard I would use whitworth as next best, as same head sizes.

I think I would buy 4 studs rather than make them, but living in NZ but that would be expensive unless they were ordered with other items.

After restoring my 3rd british bike I have only just ordered some CEI taps and dies from tracy tools in the UK, shipping added over 50% to the cost. I ordered a few sizes mainly because I needed some clutch nuts quickly (special shape for B44) and had to make them, which was very difficult without a tap. I do have cheap UNF/UNC and whitworth tap and die sets.

In the long term I would like my A10 and B44 with correct spec nuts and bolts throughout, the B31 will always be a compromise.....even some metric 

[RDfella]

When buying taps / dies best make sure they're HSS. Cheaper ones are often carbon steel. They don't last as long and won't look at harder materials. Remember too that alloy castings contain silicon which is hard on tools.

[David Tinsley]

When buying taps / dies best make sure they're HSS. Cheaper ones are often carbon steel. They don't last as long and won't look at harder materials. Remember too that alloy castings contain silicon which is hard on tools.

I am going for HSS from Tracy Tools, just the ones I need rather than a set, most of which would not get used.

[AdrianJ]

I’ve just got to the bottom of my carb studs problem! Couldn’t fit the Carburetter (276) on properly.
They should have been bolts. (Iron head)
I got a pair of the correct CEI screws, bolts being unavailable.
Tried to use them but one wouldn’t go in.
Measured the stud I’d taken out and found it was BSW so I got two BSW screws.
Again one didn’t fit.  Should have had a close look at both. One was BSW and the other was CEI.
I didn’t really expect that. Next time the head comes off they will be restored to CEI.
What I’m trying to say is, given the chance, stick with the correct screw and thread.
Adrian.