S2C Forum Archives
Main Section => Welcome to our virtual Pub Meeting ... => Topic started by: Davidss on November 16, 2019, 10:42:30 AM
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I suspect most are familliar with the mixture of threads in the Series 2, mainly UNF, BSF & BSW, with a smattering of BA, but here I'm interested in those falling outside that set, and asking for suggestions as to the source of these 'out of the ordinary' fittings. Purely for curiosity.
Example 1.
I'm following on the topic where the thread of the axle drain plug was identified as Unified National Extra Fine, a range which had its source in America.
A chance find was that a drain plug with the same part number as one of those used in the LR (241110) is also listed for all Rover P4 models by J R Wadhams (https://www.jrwadhams.co.uk/gearbox-drain-plug.html).
The P4 was introduced, so Wikipedia tells me (https://en.wikipedia.org/wiki/Rover_P4), in September 1949.
There's no surprise in its inclusion in the Land Rover, a product of the Rover Company, but how did that thread get into the Rover Company in the first place?
Wikipedia tells me that the bodywork of the Rover P4 was influenced by the 1947 Studebakers (https://commons.wikimedia.org/wiki/category:1947_Studebaker_automobiles), but that these bodies were mounted on an existing chassis, crediting James Taylor's book 'Rover P4 – The Complete Story'.
Thus it seems rash to 'blame' the Studebaker for the introduction of this thread into the axle design.
Example 2.
The other thread which appears to have travelled from America is used for the screws holding the covers on the brake and clutch pedal towers. 10x32 UNF, 1/2" long (10 Gauge, 0.192"/4.88 mm x 32 TPI) SCREW, self-tapping. Parker Kalon Type 'A', binding hd.
Initially it was tempting to think this was transferred from the LR inspirational Willys Jeep, but I know so little about the Jeep that I'm not certain.
This may not be a complete list, but they are the two unusual choices that sprung to mind.
Regards.
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Nearly as bad as MG pre 1955 engines that use bolts with metric threads, but imperial heads. Due I think to MG purchasing the rights to hotchkiss engines from France in 1920s or 30s. This is as well as the usual mix of British threads.
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The BSP thread form has been left off the list ^^^
BSP is very common for fluid fittings.
Can't add to the list of "odd" thread forms ... but why did Land Rover choose 3BA screws to fix the fuel tank sender ??? a very odd size.
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Sometime in the 30's I think various manufacturers started adopting the American 'SAE' theread system - in preference to the British BSF/Whitworth system. During the war there was a great deal of American machinery & vehicles which would have used SAE. SAE has the advantage of fine threads and small nut size - which made fitting in confined spaces easier as well as saving weight & material.
In about 1947/8 UK decided to replace WW/BSF with the Unified system which used SAE sizes (UNF & UNC). The only problem was they couldn't agree on small sizes - so BA persisted as did some strange numbered threads. In smaller sizes UNC has the same pitch as Whitworth but with a different thread form.
In the late 1930's Rover installed a new axle making plant - making spiral-bevel differentials amongst other things. This probably explains why they kept spiral bevels in cars when everyone else changed over to hypoid. (Hypoid is found in the salisbury axle used in 109's and others) The bungs were probably something that was convenient to supply - as after all when you're fittling a boss to an axle in a dedicated woorkshop - once you've decided on the thread and secured your supplies it doesn't make much difference what it is - the tools are set for that job and probably aren't used for anything else.
Some thread forms are known by many different names - We think of the brake pipe unions as 3/8 UNF - but I think they're actually NTP (National Pipe Thread) or even APT (American Pipe Thread) - which just happen to be the same at those sizes.
The MG bolts - Hotchkiss used metric - and those mending Morris cars grumbled their spanners wouldn't fit - so a Morris production manager suggested using metric bolts with imperial heads! The manager - Leonard Lord - who went on to head Morris, fall out with Morris and join Austin - then get his revenge by forming BMC. He was on the board of BMC after his retirement but unfortunately didn't stop the 1800 and the Maxi being built which of course were largely responsible for the collapse of BMC and eventually BL.
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Every time I see a job lot of taps and dies I buy them, take out what we haven't got and sell the remainder, the times we have struggled in the past for one tap!
Its surprising what sizes crop up, we do have the odd UNEF and a few left hand
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Manufacturing decisions are made, sometimes, on really bizarre sets of reasons; but they nearly always boil down to cost or convenience.
I would suspect the adoption, in the immediate post-war period, of an obscure US standard drain plug thread, would likely be down to the fact that there were vast numbers of ready made ones available because they’d been churned out to be used on Jeeps, DUKWs, tanks, or whatever, and were available at a fraction of the cost of making or buying BSP alternatives.
In a similar vein, most of the gears used in Fairey overdrives were obsolete, but cheap and “off the shelf” ones from a very common (Austin I think) major player. It meant that the gearsets were cheap to start with, although once the stock had dried up small batch economics meant that they aren’t cheap any more.
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It is not uncommon for engineers to use non standard threads. So whilst the diameter and TPI might match a different thread series, the actual thread form might be different.
I haven't measured an axle drain plug, but is it definitely UNEF? I'd be very surprised if it wasn't just a 'special' thread. A lot of my work is threading valve bodies, caps, spindle glands etc for steam fittings and a lot of these are 11tpi whit form, in round figures (2" x 11tpi, 1 1/4" x 11tpi etc) and very rarely are they stock BSP sizes (despite the fact it would be very handy for cleaning threads with taps). I assume railway workshops back in the day had taps made for all these sizes - indeed I have made a few for different jobs.
I thought the fuel sender used 2BA, as did the pedal cover screws - the latter certainly are rather crudely threaded and might be hard to ascertain without the original drawings. I doubt the parts catalogue specifies the thread on these although it might. I know the last time I talked about these on here I was accused of dangerous practice for suggesting that M5 fasteners usually fit without any tapping or alteration, owing to their crude nature :-X As a side note both my motors have stainless M5 fitted on the pedal box covers and have done for some years now - no deaths so far.
I would agree that cost plays a big part here. In my line of work the designers didn't have to worry about it too much when they drew the components as pretty much everything was made in-house, but I would have thought for Land Rover things like threaded plugs would be bought in by the thousand and probably from a UK manufacturer back then. The pedal box screws would surely match those that hold the dash in place, and the fuel sender to the top of the tank? I can't imagine there being three near identical screws all stocked. ???
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I seem to remember my late 4.6 Rover V8 had the UNC thread with metric head bolt thing. Rest of the vehicle was metric but some was metric fine.
Craig.
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I just discovered the zenith carbs have metric bolts. Prob French origin with solex being the owner I believe.
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I was wondering about the Zeniths as everything I measured to bore out the spindle bushes seemed to be metric sizes. 7mm spindle shaft for one.
Craig.
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Just to add one more, the "special" bolts that hold the spare tire on the bonnet. The heads are 15/16" to fit the wheel brace until the S3's(?) then it went to 1-1/8" along with the wheel lug nuts. I don't remember the thread size, I've got it somewhere.....
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Coming back to add to this 'list'.
A recent thread (https://www.series2club.co.uk/new_forum/index.php/topic,1573.0.html) asking about the threaded plug in the rear of the cylinder head suggests that, possibly in common with threaded plugs in the block, these are BSC (British Standard Cycle) threads. 1+3/8" x 20TPI in this cylinder head location.
Today, while composing this, I have discovered there is a Unified Extra Fine (https://www.gewinde-normen.de/en/20-un-thread.html) thread at 1+3/8" x 20TPI.
You will see that Unified Extra Fine is described as having a 60 degree flank angle, as is the British Standard Cycle thread (https://britishfasteners.com/threads/bsc.html).
Then there are the 'special screws' used to retain the end caps on 'most' steering relays.
In the main these are 1/4" BSF thread with a 2BA head.
Some users have reported finding larger heads, possibly Metric, but I don't recall details of spanner size or thread form.
I recall 'an American' reporting the issue, then noting that pictures in the TrueS2 BGS build thread showed the same size of screw head in a relay (fitted in the chassis, I think).
Regards.
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Manufacturing decisions are made, sometimes, on really bizarre sets of reasons; but they nearly always boil down to cost or convenience.
I work in a development environment, and I can assure you much of what gets done has everything to do with bad-practice, and low-cost. Good engineering has nothing to do with large parts of it. How stuff can be maintained is not our problem, in fact if it can be a little awkward this often serves its own purpose.
Transfer sump plug is: 1-1/8" x 16TPI / 0.0625 Inches Pitch / 1.588 mm Pitch
There can be no engineering reason for such as obscure thread. But it's there.
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I think that's the same thread as the diff & fuel tank drain.
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Interesting thread.
Re the 2ba screws for the dashboard and brake cylinder covers. Its quite a few years since I rebuilt my Landy, but if I recall correctly It was difficult to find a supplier of these panhead screws. Both for these and similar fixings, might be helpful If posters could offer suggestions for suppliers if they know any?
Regards
Alchad
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Indeed an interesting topic, there must have been huge quantities of surplus threaded components available post WW2 both ours and yank stuff, so clearly made economic sense to use this whenever feasible..
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Hells teeth.....thought I'd have a quick Google to see if it was any easier 2 years on. Certainly found some, but 75p each !!
https://www.spaldingfasteners.co.uk/2ba-zinc-plated-steel-pan-slotted-head-machine-screws/
compared to 6p for cheese head?
https://www.spaldingfasteners.co.uk/2ba-ba-zinc-plated-steel-cheese-slotted-head-machine-screws/
What gives?
Alchad
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You may find that 2BA purchased from your favorite LR parts suppliers under their part number are more reasonable.
Also 5mm panheads are very cheap and no problem if they are for a through bolting application.
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Must have changed nearly 500 fixing on my suffix c S2a, for stainless in most cases. The only (1/4") UNC thread I found was holding the front of apron onto tapped hole in chassis. Not to say there aren't others of course.
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Re the 2ba screws for the dashboard
The ones I used were branded 'Britpart'. You could tap them out to M5 - a couple of the threads on my clutch pedal box were stripped, so were tapped out.
I used Namrick metric stainless pan heads where practicable.
Sunny Jim
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Just to add one more, the "special" bolts that hold the spare tire on the bonnet. The heads are 15/16" to fit the wheel brace until the S3's(?) then it went to 1-1/8" along with the wheel lug nuts. I don't remember the thread size, I've got it somewhere.....
1-1/8" or 1-1/16"? My 1970 S2A has a full set of wheelnuts for which I need a 27mm socket except for one "odd" 15/16" one. 1-1/16" = 26.9875mm so near as dammit for the socket fit.
I've been told that these 1-1/16" (27mm?) nuts with the same stud thread as the normal 15/16" ones are only found at hen's dentists or behind incontinent rocking horses. Can anyone help with one? It would be nice to have a full set!
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Like this?
https://www.paddockspares.com/576103-wheel-nut-1-1-16in-1969-1971.html
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That looks like it! Thanks for the pointer.
One for £0.26 sounds good, but one for £5.26 (inc shipping) might have to wait a bit.
:cheers
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Is 9/16" the stud diameter of your vehicle?
Regards.
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Yes. It's the same thread as the earlier 15/16" AF wheelnuts.