Whit Form threads

[Bill PhinnParticipant @billphinn90025]

What is a Whit Form thread? From what I can deduce it is the same in essence as a BSW or BSF thread but with a TPI that isn’t standard BSW or BSF.

Am I right, and is that all there is to it?

I can’t see any mention of Whit Form threads in my copy of Machinery’s Handbook, nor any discussion online. Whit Form taps and dies appear to be still commercially available.

What has prompted my post is that I’ve got an English-made bookbinder’s typeholder (around 100 years old) with adjustment screws that have 1/4″x24 threads. Is it likely these are Whit Form? I’ve not measured the flank angle yet.

Any general information on the origin, prevalence, and uses of Whit Form threads would be appreciated.

[Michael GilliganParticipant @michaelgilligan61133]

Yes, Bill … Whitworth Form refers to the shape of the thread NOT its pitch.

That’s really all there is to it.

MichaelG.

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Edit: __ this diagram ‘says it all’

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https://en.wikipedia.org/wiki/British_Standard_Whitworth#/media/File:Whitworth_Thread.svg

 

[Michael GilliganParticipant @michaelgilligan61133]

No idea why, but Tracy Tools has Taps and dies:

https://www.tracytools.com/product/1-4-x-24-tpi-w-form/

 

MichaelG.

[JourneymanParticipant @journeyman]

Sir Joseph Whitworth proposed this thread in 1841. This was the first standardised thread form. The form of the thread is shown in the diagram. The principal features of the British Standard Whitworth (BSW) thread form are that the angle between the thread flanks is 55 degrees and the thread has radii at both the roots and the crests of the thread. The relevant standard for this thread form is BS 84: 1956.

John

[Bill PhinnParticipant @billphinn90025]

Thanks for your replies, Michael and John.

Michael’s first answer confirms what I suspected.

Whit Form are bundled into a separate category from BSW and BSF presumably because their pitches disqualify them from being British Standard Whitworth or British Standard Fine.

Tracy Tools (whose pages helped me tentatively identify my 1/4″x24 thread prior to my first post) offer a surprising 137 different Whit Form threads in taps and dies. Their BSW and BSF offerings, only 53 in total, don’t even come close in number.

I can’t help feeling there’s a certain contempt for Whitworth’s enlightened desire to do away with the “Babel” of innumerable different screw threads in the proliferation of these Whit Form threads.

Presumably, since they have the same thread form, they came after the establishment and widespread adoption of Whitworth’s standard, not before.

Why did so many of these non-standard Whitworth threads become established in their own right? The occasional lathe operator single-point cutting a Whitworth thread with a non-standard pitch now and again is understandable, but the fact that commercially produced taps and dies are available in 137 different Whit Form threads suggests they weren’t just occasional departures from BSW and BSF, but reasonably common in their own right for quite some time.

Why? Who was using them? And, apart from bookbinders’ tools, on what?

[bernard towersParticipant @bernardtowers37738]

Surely it’s just a case of the manufacturer of an item used the WF but at their dia wanted a tpi more suited to their dia/material and required strength.

[Wade BeattyParticipant @wadebeatty78296]

My Leinen Lz43 headstock thread is a 55 degree 3.5mm pitch with a 44.5mm diameter..

 

[Wade Beatty]

On Wade Beatty Said:

My Leinen Lz43 headstock thread is a 55 degree 3.5mm pitch with a 44.5mm diameter..

 

I’m not quite sure what I’m to infer from that.

The thread seems pointlessly close to 1.3/4″ BSF. More crucially for our purposes, there is no Whit Form tap or die for it, so the thread clearly wasn’t very widespread.

[Michael GilliganParticipant @michaelgilligan61133]

I hesitate to suggest this, Bill … for fear of triggering  ‘hate’ [*] from the proponents of other thread forms … but, I think the Whitworth thread form was widely adopted because engineers recognised:

1. its technical merits
2. its geometric elegance, and
3. all the effort that went into producing and standardising it

It was, and remains, a fundamentally good design … and Sir Joseph Whitworth was widely respected.

Bottom line … If you wanted a good form for screw-thread; why choose any other ?

It was [as intended] definitive.

MichaelG.

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[*] an unpleasant word which has now settled in the vocabulary of this group

[NealebParticipant @nealeb]

The number of available taps and dies presumably reflects the fact that while a standardised thread form is highly desirable, and many needs are satisfied by the common BSF/BSW thread pitches, there is also the need for other pitches – often finer. We have the Model Engineer threads, typically 32 or 40TPI, British Standard Brass (26TPI) and so on. Not sure about the cycle, pipe, etc, threads! All Whit form, and still in use, although probably this is decreasing. When I look at the thread chart on my workshop wall (kindly supplied by Tracy Tools, conveniently a mile or so from a favourite local supermarket!) I see that even metric threads have “common” sizes but there are probably around three times that number listed, mainly in finer pitches.

[Bill Phinn]

On Bill Phinn Said:

 

 

Why did so many of these non-standard Whitworth threads become established in their own right?

Because we are not just talking about nuts and bolts. For example BSW & BSF are no use for a pipe union. A much finer thread is needed.

[Mark RandParticipant @markrand96270]

It should be noted that the standard ISO metric pipe thread is also of a Whitworth form. That’s because it’s BSP 😀 .

Truncated thread forms aren’t that bright an idea when trying to seal liquids and gasses!

[Rod RenshawParticipant @rodrenshaw28584]

I seem to remember reading that metric pipe sizes, and their threading standards, are basically Imperial ones,  but notated (If that’s the right word) in metric units. So a metric 152.3 mm diameter pipe is really the same as a 6 inch pipe. Is this basically correct? I know there are numerous different standards for pipes and tubes of different materials and for different purposes but it does seem as if the Continentals borrowed the British pipe and thread dimensions as fit for purpose but measure the pipes with their own rule. If so, it seems like a tribute to Whitworth and his work.

[Martin ConnellyParticipant @martinconnelly55370]

Where I worked we bought NB pipe (USA ANSI B36)from stockists who sourced it from any supplier who had what they wanted at a price that suited their needs. This meant we sometimes got 2″ pipe that had been made in Italy, for example, that as well as having the NB size printed on it also had the metric size on it. So it would be marked ANSI B36 2″ NB Sch10 and 60.33mm x 2.77mm followed by the ASTM A.213 material designation such as 316L. So a mixture of standards and units.

Martin C

[Howard LewisParticipant @howardlewis46836]

Whitworth form threads are used in BSW, BSF, BSP, BSB (British Standard Brass) and Model Engineer threads, All of which have their own pitch or pitches. The only ” constant pitch” across all sizes are the BSB at 26 tpi, and the ME threads at 40 tpi and 32 tpi.

There will be other “non standard” pitches, (The early Myford ML1,2,3 and 4, used 7/8 BSW, and then 7/8 x 12 tpi, the “Standard” Myford 1.125 x 12 tpi.  The Warco BH600, BH900, Chester Craftsman, Engineers ToolRoom BL12 -24 all use 2.25 x 8 tpi for the chuck mounting, as no doubt, will other Taiwanese generic lathes.

Posibly Boxford will use a Whit form thread, to distinguish from the South Bend.

Sometimes a “non standard” pitch will be used, deliberately, sometimes to try to maintain a market for spare parts, or finer pitch than the standard for a given diameter, to provode a more precise adjustment.

R P S threads, used in older cameras, lenses and enlargers will be Whit form, but with a finer than standard pitch, plus microscopes.

Howard

[Bill Phinn]

On Bill Phinn Said:

…commercially produced taps and dies are available in 137 different Whit Form threads

I think you are trying to draw conclusions on too small a sample (i.e. a sample size of one).

If you were to research diameter and pitch combinations of Unified threads, I wonder what number you would reach? There are at least two Unified constant pitch series which must add considerably to the total. Where would 5C collet threads (internal and external) fit in your analysis?

If you were to research ISO metric threads, what total would you reach?

Have a look here:

https://www.gewinde-normen.de/en/index.html

[bernard towersParticipant @bernardtowers37738]

As Howard states to maintain a spares supply,  one case in point is the front screws on coventry die heads, the most lost part!!!

[BaldricParticipant @baldric]

For screwed stay in a full-size boiler, they are constant pitch, GWR was 11TPI, I know that some other boiler makers used 12TPI, that allowed for a stay to be drilled out & tapped to a larger size without any issue of a different pitch causing a leak where part of the old pitch still existed.

[Michael Gilligan]

On Michael Gilligan Said:

… but, I think the Whitworth thread form was widely adopted because engineers recognised:

1. its technical merits
2. its geometric elegance, and
3. all the effort that went into producing and standardising it

It was, and remains, a fundamentally good design … and Sir Joseph Whitworth was widely respected.

Bottom line … If you wanted a good form for screw-thread; why choose any other ?

It was [as intended] definitive.

MichaelG.

 

Not how I read the history.  Whitworth came up with something far cleverer than a mere thread – standardisation.  Given a decent thread, and clear instructions on how to make it, most firms preferred to standardise, not least because they could sack everyone making proprietary threads and buy in cheap mass produced nuts and bolts.  Also made sales easier, because customers dislike being forced to buy proprietary spare parts.

Whitworth form was excellent in it’s day, but two faults gradually emerged:

• Coarse threads are suitable for soft-materials, great when Victorian engineering majored in cast-iron, but not good for steel, or the small diameter nuts and bolts needed for instrument or electrical work.  As these industries developed, it became necessary to think again.
• The rounded form is expensive and fiddly to make, and the extra strength rarely needed. Rounding made good sense when Wrought-Iron bolts went into cast-iron bodies, but unnecessary as materials changed, and for most ordinary purposes.

Rather later in the US, Sellers looked at Whitworth and liked the idea but not the detail.  He decided to simplify, making US industry more productive and cheaper than British industry.  Sellers removed the rounded top and switched from 55° to 60° and this became the US National thread.   Main advantage was standardisation, not geometric elegance!

In the same time-frame, the Europeans standardised on Metric measurement.   In Europe, metric was very much welcomed because it replaced a gazillion local measurements that caused endless trouble with trade.  Europe and the rest of the world also went for 60°.  Metric and US thread forms are very similar, apart from metric being defined in terms of metric pitch, and US being defined in Threads per Inch.

In WW2 the difference between American and British fasteners caused endless trouble, and it was decided to standardise on a Unified System, which is closer to the US National form than Whitworth, thus BSW and BSF started to decline during the 1950s.   UNC and UNF didn’t last long in the UK, because we faced sharp competition from Metric countries, none of whom wanted Inch based fasteners.   By the 1960s the figures showed that most export customers wanted Metric, not Whitworth or UNC/UNF.   Not accepted on many shop-floors and Board Rooms unfortunately, where too many fought tooth and nail to keep the old ways.

My conclusion, ‘the customer is always right’.  And when customers no longer want something, no matter how glorious, the supplier has to move on.

Mistake I suggest to support any technology for sentimental reasons.  Technology is about fixing today’s problems.  Although HMS Victory was arguably the best warship in the world, and has an amazing history of achievement, I hope no-one thinks the ship has any place in a modern Navy.   Likewise, the much more modern USS New Jersey. She too was excellent in her day, but designed for a role that no longer exists, and although not quite obsolete yet, would need major upgrades before she could safely be deployed. Spending big money on technology that’s not needed is always unwise – I see the ship soon becoming a museum piece.

Post Brexit, the government launched a consultation to find out if legislative change was wanted in respect of Imperial and Metric measure.  During the Brexit campaign, there was loud support for Imperial.  The consultation results  are in, full report here.  In summary, the UK emphatically does not wish to undo Metric in favour of Imperial:

 

 

 

Imperial measure served this country well, but clinging to it after 1965 was – in my opinion – a bad mistake. Kept traditionalists happy, but thoroughly confused industry and damaged their ability to sell abroad.

Dave

 

 

[Bill PhinnParticipant @billphinn90025]

Thanks to everyone for your replies. They’ve clarified a number of things for me.

The two main points, dealt with by Bernard, Nealeb and DC31K among others, seem to be that:

a). As industry evolved, the standard range of BSW and BSF threads was never going to be a big enough range of pitches for all purposes. The same applies to other thread forms; a glance at Tracy Tools Metric fine offerings (numbering 134) for example tells me that the handful of Metric coarse and fine pitches most of us regularly encounter are only the tip of a large iceberg.

b). This proliferation in the range of Whitworth, Metric, Unified and other threads since Joseph Whitworth’s day (whose house “The Firs”, incidentally, is less than two miles from mine) is not at all at odds with his desire to standardize screw threads, merely a reflection of real-world need and the inevitable evolution of different thread standards that not all countries or individuals have shown an equal enthusiasm for.

I think what troubled me most (and continues to do so) is the messiness of the terminology and the inconsistency in the way different thread forms are classified. Metric appears to be the simplest (I exclude BA), with coarse and fine, but classification of Whitworth and Unified begins to get rather untidy, with other categories (not necessarily containing finer threads) added on to their coarse and fine categories. It certainly could be clearer, or at least more consistent, if the right people put their minds to it.

I’m left wondering whether I will ever encounter another Whit Form thread again on an item besides the 1/4″x24 on my typeholder. I’m not much more aware now than I was at the start of this thread what sorts of things Whit Form* threads are to be found on.

*Hopefully it is clear by now what I and Tracy Tools mean by Whit Form threads, i.e. not BSW or BSF.

 

[Martin of WickParticipant @martinofwick]

That’s the great thing about having engineering standards….. there are just so many you can chose from!

And if you don’t like what you’ve got, just invent a few more!

WaaHaaHaa  ha! (carries on banging head against wall).

 

It’s an age thing, the older the product, the more likely it will be to have weird and wonderful bastard thread sizes and if old Britiron, whitform is the bastard of choice. But save your contempt for the real villains, the ones that insist on using miscellaneous varieties of thread systems on the same item, Myford for example (metric, whitworth as well as whitform and if you are lucky BA!)

[SillyOldDuffer]

On SillyOldDuffer Said:

On Michael Gilligan Said:

… but, I think the Whitworth thread form was widely adopted because engineers recognised:

1. its technical merits
2. its geometric elegance, and
3. all the effort that went into producing and standardising it

It was, and remains, a fundamentally good design … and Sir Joseph Whitworth was widely respected.

Bottom line … If you wanted a good form for screw-thread; why choose any other ?

It was [as intended] definitive.

MichaelG.

 

Not how I read the history.  Whitworth came up with something far cleverer than a mere thread – standardisation.  …

 

You are entitled to your ‘reading’ Dave, as I am to mine … but I am genuinely disappointed that you have strayed so far from the point.

We were discussing the Whitworth Thread Form, and Forms do not depend upon units of measure, or upon size; they are simply a shape.

MichaelG.

.

P.S. __ off Topic: the presentation of quoted text on this forum is even worse that it first appeared … why, Oh why! is my numbered list displayed like that ?

[Dave HalfordParticipant @davehalford22513]

A Whit form thread

A thread that would be a Whit thread tap/die size, but without the correct tpi/diameter and still have sufficient strength for the purpose.

eg 4C collets are threaded 20tpi and over 3/4″ in diameter whereas the corresponding proper Whit size dia for 20pti would be 1/4″.

I would expect that a Whit form would conform to the Whit rules of flank angle and rounded tops, which therefore locks in both thread depth and tpi together.

[GeorgineerParticipant @georgineer]

A couple of relevant points:

The British Brass Thread isn’t, and has never been, a British Standard;

There is a truncated (or modified) version of the Whitworth thread, though I have been unable to establish if it has ever been a British Standard or whether it’s just One of Those Things.

George

[old martParticipant @oldmart]

The closely related BSC cycle threads are 60 degrees and not the Whitworth 55 degrees, and BA are an odd metric based thread.

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