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Whitworth / BSW tap and die question???
- Thread starter timbn2
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Healeysince59
Jedi Warrior
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Early 4 cyl Healeys have fasteners that require Whitworth wrenches but they are seldom BSW (British Standard Whitworth), they are BSF (British Standard Fine). You will occasionally find BSW in threads tapped in aluminium. I have a BN1 and a TD and I don't think I have ever used the BSW tap set I bought years ago. A lot of BSF fasteners have Whitworth hex sizes and require Whitworth wrenches but that doesn't make them Whitworth threads.
Marv J
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BUNDYRUM
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BSF is a Whitworth thread form, meaning it has the same thread angle but it is a finer thread, i e it has more threads per inch than the BSW.
The Whitworth thread started out as being a coarse thread only and later they made fine threads which is why they are the same form.
It took the British a long time to understand about aluminum/cast iron and fine threads and why it shouldn't be done (at least not successfully).
Yes SU's on all model Healey have Whitworth threads and BSP (pipe) threads because they didn't want to change.
There is actually a "cycle" thread form also which has a lot more threads per inch than anything else.
bundyrum.
The Whitworth thread started out as being a coarse thread only and later they made fine threads which is why they are the same form.
It took the British a long time to understand about aluminum/cast iron and fine threads and why it shouldn't be done (at least not successfully).
Yes SU's on all model Healey have Whitworth threads and BSP (pipe) threads because they didn't want to change.
There is actually a "cycle" thread form also which has a lot more threads per inch than anything else.
bundyrum.
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Bundyrum, I agreee with you totally. According to Anderson & Moment in the "Authentic Restoration Guide" ...
"Whitworth fasteners were only used in a few applications on the four-cylinder cars, such as attaching the adjusting link to the generator front plate, and were not used on the six cylinder cars. ... on the Hundreds, the fine thread fasteners were threaded to the British Standard Fine (BSF) standard. ... In 1954, a new 'Unified' system was introduced that used Unified National Coarse (UNC) and Unified National Fine (UNF) standard threads on bolts. UNF and UNC threads are respectively compatible with American Society of Automotive Engineers (SAE) and United States Standard (USS) hardware. ... The change over was largely completed before the six-cylinder Healeys went into production."
"Whitworth fasteners were only used in a few applications on the four-cylinder cars, such as attaching the adjusting link to the generator front plate, and were not used on the six cylinder cars. ... on the Hundreds, the fine thread fasteners were threaded to the British Standard Fine (BSF) standard. ... In 1954, a new 'Unified' system was introduced that used Unified National Coarse (UNC) and Unified National Fine (UNF) standard threads on bolts. UNF and UNC threads are respectively compatible with American Society of Automotive Engineers (SAE) and United States Standard (USS) hardware. ... The change over was largely completed before the six-cylinder Healeys went into production."
OP
timbn2
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BUNDYRUM
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Tim I looked at the set of taps and dies you highlighted and I don't think you need to go this route.
If you "google" taps and dies you will find any number of sets available for a lot less money. I'd be surprised if there wasn't something on BCF webiste.
A set usually comes with Fine and Coarse thread taps and dies.
I don't think you could say that one size will fit all here as I'm not sure what threads are on the BN2 but if you hold a UNF tap up to the threads to see if they match that should tell you.
vette: I don't see why Tim should have to buy "metric" as they will be of no use to him. The pitch of the thread doesn't come close to the Whitworth. Once again BSF is a Whitworth thread form. It has a 55 degree thread angle whereas the "unified" thread form has 60 Degree thread angle.
If Dave Russell is reading this he should know as he has a BN2.
bundyrum.
If you "google" taps and dies you will find any number of sets available for a lot less money. I'd be surprised if there wasn't something on BCF webiste.
A set usually comes with Fine and Coarse thread taps and dies.
I don't think you could say that one size will fit all here as I'm not sure what threads are on the BN2 but if you hold a UNF tap up to the threads to see if they match that should tell you.
vette: I don't see why Tim should have to buy "metric" as they will be of no use to him. The pitch of the thread doesn't come close to the Whitworth. Once again BSF is a Whitworth thread form. It has a 55 degree thread angle whereas the "unified" thread form has 60 Degree thread angle.
If Dave Russell is reading this he should know as he has a BN2.
bundyrum.
Roger
Luke Skywalker
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BUNDYRUM said:
B.S. I have worked on really early British Aluminium crankcases etc., and without fail they had coarse threads on the studs - yes, they mostly used studs rather than bolts, because that's better engineering too!
If youmake a sweeping statement like that, you'd better come up with some examples, please.
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Hello Bundyrum, I'm not an expert on threads, but I believed the Healeys at least after 1955 didn't have much Whitworth. But I guess previous to that they may have more than I have experience with. I've only got metric and SAE and it seems I've had what I need. I'm afraid I'm all played out on this one. Don't know anymore about it.
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BUNDYRUM
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Roger, Yes it seems that was a bit of a broad generalisation I made I'm sorry for that. Maybe I'll just confine it to BMC.
When you look at any Healey engine, gearbox or rear end there are not a lot of coarse threaded fasteners to be seen. That goes for either aluminum or iron castings. Yes there are a lot of studs in those castings but they are still fine threads.
It's not as though the casting material was any great high strength alloy especially when it came to the aluminum. The main reason they didn't use a high strength alloy was it wasn't around, ie it hadn't been invented.
It's only pistons that were available in those days that came close to a high strength alloy but even those were only used for racing purposes.
Once again sorry for the sweeping statement.
Regards,
bundyrum.
When you look at any Healey engine, gearbox or rear end there are not a lot of coarse threaded fasteners to be seen. That goes for either aluminum or iron castings. Yes there are a lot of studs in those castings but they are still fine threads.
It's not as though the casting material was any great high strength alloy especially when it came to the aluminum. The main reason they didn't use a high strength alloy was it wasn't around, ie it hadn't been invented.
It's only pistons that were available in those days that came close to a high strength alloy but even those were only used for racing purposes.
Once again sorry for the sweeping statement.
Regards,
bundyrum.
Roger
Luke Skywalker
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So it wasn't the engineers, it was the cost accountants? They and the unions wrecked the British motor industry one way or another.
If you look at a 1920s Austin gearbox or crankcase it'll have double-ended studs - BSW one end, BSF the other. BSW end goes into the aluminium, the fine thread is for the nut. I guess Healeys have both ends fine? Cheaper and nastier to make I suppose.
Ive worked on pre-WW1 motors with double-ended studs too, like a 1913 V-twin Humberette for example.
If you look at a 1920s Austin gearbox or crankcase it'll have double-ended studs - BSW one end, BSF the other. BSW end goes into the aluminium, the fine thread is for the nut. I guess Healeys have both ends fine? Cheaper and nastier to make I suppose.
Ive worked on pre-WW1 motors with double-ended studs too, like a 1913 V-twin Humberette for example.
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Wow - I'm not sure it can be simplified. BN1 & BN2's were a confusing mix of wrench & thread sizes.
For example, a 7/16" bolt shank can have several thread pitches & bolt head sizes.
A 7/16 bolt can have 18 tpi - BSF, 14 tpi - BSW, or 20 tpi - UNF. This same bolt can require a 7/16W, 1/2BSF, 5/8UNF, or 11/16 wrench.
There are exceptions everywhere. For example the standard head studs are 7/16-18BSF on both ends, but have a nut which requires a 3/8W wrench instead of the more common 7/16W. The new high tensile head studs are 7/16-18BSF on the block end & 7/16-20 UNF on the nut end, & require an 11/16 wrench.
There are quite a few non standard bolt threads & head sizes throughout the car.
As Bundy said:
"The pitch of the thread doesn't come close to the Whitworth. Once again BSF is a Whitworth thread form. It has a 55 degree thread angle whereas the "unified" thread form has 60 Degree thread angle."
-- Don't mix 55 degree & 60 degree thread forms.
My best advice is to never force a tap or die or nut if it doesn't want to go easily.
Get BSF, & UNF taps. Get BSW taps only if you determine one is really needed. Get dies only if desperate, see below.
You will also need some Whitworth wrenches.
If in doubt, get new hardware from Moss that matches the exact application. Even if you are only getting two or three at a time. A few new bolts or studs can be much cheaper than buying the required dies.
D
For example, a 7/16" bolt shank can have several thread pitches & bolt head sizes.
A 7/16 bolt can have 18 tpi - BSF, 14 tpi - BSW, or 20 tpi - UNF. This same bolt can require a 7/16W, 1/2BSF, 5/8UNF, or 11/16 wrench.
There are exceptions everywhere. For example the standard head studs are 7/16-18BSF on both ends, but have a nut which requires a 3/8W wrench instead of the more common 7/16W. The new high tensile head studs are 7/16-18BSF on the block end & 7/16-20 UNF on the nut end, & require an 11/16 wrench.
There are quite a few non standard bolt threads & head sizes throughout the car.
As Bundy said:
"The pitch of the thread doesn't come close to the Whitworth. Once again BSF is a Whitworth thread form. It has a 55 degree thread angle whereas the "unified" thread form has 60 Degree thread angle."
-- Don't mix 55 degree & 60 degree thread forms.
My best advice is to never force a tap or die or nut if it doesn't want to go easily.
Get BSF, & UNF taps. Get BSW taps only if you determine one is really needed. Get dies only if desperate, see below.
You will also need some Whitworth wrenches.
If in doubt, get new hardware from Moss that matches the exact application. Even if you are only getting two or three at a time. A few new bolts or studs can be much cheaper than buying the required dies.
D
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BUNDYRUM
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timbn2.
Just so you are a little bit more aware, SAE and UNF are the same thing.
If you have any more questions we are most willing to confuse you a bit more than you thought possible.
But seriously we have all been where you are at present so keep those questions coming.
bundyrum.
Just so you are a little bit more aware, SAE and UNF are the same thing.
If you have any more questions we are most willing to confuse you a bit more than you thought possible.
But seriously we have all been where you are at present so keep those questions coming.
bundyrum.
JeffS
Jedi Trainee
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I'm surprised no one mentioned BA threads as well. Those are also on your car, probably more prevalent than BSW. You'll find 2BA and 4BA on your distributor, 3BA on your gauge fixings. Probably other places as well.
Britishfastener.com sells great taps and dies individually or in sets if you need them. If you can't identify a thread pitch, you can send them a fastener to identify as well!!!
Britishfastener.com sells great taps and dies individually or in sets if you need them. If you can't identify a thread pitch, you can send them a fastener to identify as well!!!