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MG TD TF 1500 - Whitworth Nighmares

I need to get my head straight. Just spend another evening filling out my excel spread sheet with all the frame and body fasteners. (Just about done).

This is a compilation of the list in Green's restoration book, Chris Coopers List, Abindon's list, and my measurements from an unmolested TD frame.

I am still confused on the whitworth head measurement.
I read about it on the internet and it just has me more confused.

When I look at a 5/16 whitworth spanner, what is the 5/16 referring to? The spanner appears to be larger than 5/16.

Example of where this has me baffled. List says the bolts that bolt the A pan to the wishbones is 5/16 BSF X 7/8" outside bolts and 1" inside bolts (That matches my observation on the frame)

But when I look at my 5/16 spanner, I know that head would be to large for the smaller bolts used for the A pan.

I know you folks are great at explaining things, so I appreciate your input.
Bruce Cunha

Bruce,

When you see a 5/16 Whitworth spanner, it means that it will fit the head of a bolt that has a 5/16 inch diameter threaded portion. So, that 5/16 spanner might be getting up around what a regular 9/16 spanner would be.

Charley
C R Huff

The Whitworth thread was the worlds first standardised thread, designed by engineers for engineers. What mattered to them in specifying a bolt was how strong it was likely to be. This was at a time when there were far fewer grades of steel and treatment processes and the key strength factor was bolt diameter. Hence they used bolt diameter to specify the thread size. Using the head to specify bolt thread is to make it simple for a modern world where everyone likes to think they can be an engineer.
Dave H
Dave Hill

Just to confuse things further, Whit and BSF bolts originally had different head sizes for the same bolt diameter. That is why older spanners are marked say 1/2"W--9/16 BSF, tightening levels were set by spanner length the BSF required less torque for the same clamp strength.
When I served my apprenticeship as a mech fitter in the 1950's some of the equipment I worked on were pre-war and still had some of the old bolts, confusing at times.
I am still carrying some of the "Snail" brand spanners I had issued in 1955 in the TF.
Ray TF 2884
Ray Lee

I was confused, too.

This is from a blog that explains Whitworth and British Standard Fine markings better than any I have seen. Now I understand.

"Sir Joseph Whitworth (1803-1887) presented his system in Great Britain in 1841. Initially, he proposed only a coarse thread (which became known as British Standard Whitworth, or BSW or just plain W). Much later (67 years later, actually, in 1908) a fine thread was added: British Standard Fine (BSF or BS). For any given bolt shank diameter, the BSF series used a smaller nut than the BSW series. Hence, most British wrenches carry two markings on each jaw, since the same jaw opening will fit a bolt head or nut on a bolt on a given diameter of bolt with a coarse thread, and the bolt head or nut on the next size greater diameter of bolt with a fine thread."

Chart that is in the blog:
http://drive.google.com/file/d/0By95K3Kiwg5XZ2hySXBFNWEzUjg/view

Link to full blog (long)
http://progress-is-fine.blogspot.com/2017/01/the-evolution-of-standard-wrench-sizes.html

Of course, engine and gearbox Mad Metric fasteners with metric fine threads and W/BS heads are another nightmare.

Hiram Kelley used an excellant method of describing the location of each fastener in his list of "TD Tub Wood Fastners". He described the pieces connected by the fastener by giving the Moss illusration number from the appropriate diagram in the Moss catelog. Link on Bud Krueger's ttalk.info site:
http://www.ttalk.info/TD_Tub_wood_screw_sizes.pdf

Lonnie
TF7211


LM Cook

Correction:

The first column of my chart should say
"Nominal Bolt Shank Diameter - BSF Threads"

My sockets have both W and BS markings. But my wrenches have only W markings. Neither the across-the-flats measurement of the head, nor the shank diameter of a BSF threaded fastener correspond to the W designation of the wrench. Bruce, you're not the only one who has been baffled by the Whitworth labeled wrenches.

Lonnie
TF7211
LM Cook

Thanks. That helps. I did read where they changed the size of the head during WWI to save metal.

I also like the one about why the odd match with the engine. What I read is that a french engine company was purchased and they used metric, but as most mechanics had W tools, they just changed the heads so the shops tools would work.


I did find the list from Mr. Kelley. I will be incorporating that into my list (I will be crediting all of the people that the list is compiled from)

My car is fully apart and the bolts used that had nuts on them were changed to american threads, so I have few examples.

Could someone put a spanner on the A pan to wishbone bolts and tell me which fits? Again, the lists say 5/16. But a 5/16 spanner looks way large for the bolts that held the A pan to the wishbone. I would thing the head is more like 1/4
Bruce Cunha

One of the fun things about translating various lists is figuring out what is being said.

So, here is the Green list front fender.

5/16 BSF 7/8 Hex Bolt 4 Right Front Fender
5/16-18 7/8 Hex Bolt 1 Right Front Fender


So what thread is a 5/16-18

And why would there be only one of these and 4 of the BSF?
Bruce Cunha

Bruce - To my knowledge, there is only one actual Whitworth fastener in the TDs, that is the bolt that holds the generator adjusting link to to the generator. The rest of the fasteners used in the TD are British Standard Fine bolts with British Standard Fine heads, which are one size down from the British Standard Whitworth head (i.e. A 1/4 BSW has a head size, whereas a 1/4 BSF head size one notch down from the standard Whitworth head, thus the head size is 3/16 Whitworth head).

I am in the hospital for chemo therapy for lymphoma, so if you will e-mail me, I'll send you the various write ups that I have regarding the British Standard Bolt sizes vs. head sizes and how all this came about.

As an aside, Whitworth was the first one to standard fastener sizes and head sizes.
Cheers,
DW DuBois

Dave. Hope everything goes well.

From what I read, there was a change in WWII in the size of the Whitworth head.

"However, in World War II the size of the Whitworth hexagon was reduced to the same size as the equivalent BSF hexagon purely to save metal during the war[citation needed] and they never went back to the old sizes afterwards. Thus it is today uncommon to encounter a Whitworth hexagon which takes the nominally correct spanner."

So you are correct.

I am still confused over what is listed as head size as my above post details.

My end wrenches are German Chrom-Vandium and only have a single number on each end.

I need to order a lot of bolts for my restoration and as I am attempting to bring the car back to where it was when it left the factory, I need to assure I am ordering the correct ones. Moss and Abindon's bolts may or may not be correct for each application on the TD according to what I am finding. (as neither give the actual size of the bolts in their kits, it makes it hard to assure they match the printed lists I have found)
Bruce Cunha

Hi Dave,

Just wanted to wish you well on your road to recovery. You deserve the best.

Cheers
Rob Grantham
Rob Grantham

To give some visualization to the issues I am running into.

Here is Green's list of fender fasteners:

5/16 BSF 7/8 Hex Bolt 4 Right Front Fender
5/16-18 7/8 Hex Bolt 1 Right Front Fender
5/16 BSF Nut 4 Right Front Fender
5/16-18 Nut 1 Right Front Fender
5/16 1 Flat Washer 8 Right Front Fender
3/8 BSF 1 Hex Bolt 2 Right Front Fender
3/8 BSF Nut 2 Right Front Fender
3/8 1 1/4 Flat Washer2 Right Front Fender
5/16 BSF 3/4 Hex bolt (set screw)2 Left Front Fender
5/16 1 Flat Washer 5 Left Front Fender
5/16 BSF Nut 3 Left Front Fender
5/16 BSF 1 Hex Bolt 1 Left Front Fender
3/8 BSF 1 Hex Bolt 2 Left Front Fender
3/8 BSF Nut 2 Left Front Fender
3/8 1 1/4 Flat Washer2 Left Front Fender
3/8 sheet metal screw1 Left Front Fender
3/4 Flat Washer 1 Left Front Fender
1/4-20 wing nut/bolt 1 Left Front Fender

Here is what Chris Cooper has on his list.


Name Qty Logo Wrench Thread Length Finish Washer Nut
Front 4 Newton R 1/4 W BSF FW 1/4
Bruce Cunha

Continuing with the above.

Abingdon's has 5/16 x 3/4 BSF x 8

The bolts that came off my car are 1/4 (by my whitworth wrenches) and are .705 long. under head to edge using a micrometer. That is just shy of 3/4.

So is Green and Abingdon incorrect or are they using a different measurement?

I am assuming the 3/8 bolt are the ones that go through the dumb iron, but that also seems to be an odd size.

All the lists I have found have these discrepancies. This is one of the reasons I wanted to try and come up with a formal list of the body and frame fasteners.
Bruce Cunha

Bruce,

I believe the 5/16-18 refers to a 5/16 inch BSW or Whitworth bolt which has 18 threads per inch. Similarly the 1/4-20 wing nut mentioned later is a 1/4 inch Whitworth with 20 threads per inch.

Michael
M R Calvert

I have ordered Green's restoration book to see if he clarifies things.

I am also going back to my friends with the unmolested frame and use a spanner on each bolt to positively identify the head size.
Bruce Cunha

Dave, here’s hoping the chemo goes well.

Bruce are you going to continue the good work with a list for TFs? I think I have found at least one more Whitworth thread on my TF, and I think it is original, that’s a 3/16W in the Muzak metal clamps on the adjuster for the bonnet catches.

Chris
C I Twidle

Dave,
I too spent a long time in the hospital for non Hodgkins Lymphomia last year . I am now back home driving my TD this morning for fall colors. If you would like to commiserate please feel free to email me at efhask at roadrunner dot com.
Ed
efh Haskell

I don't want to add more confusion but this probably will.

One other difference between BSF/BSW and UNF/UNC is the angle of the V on the threads.
It cannot be seen with the eye but the angle on the British fasteners is 55 degrees and the American (and Metric) fasteners are 60 degrees.

Thus even though Witworth fasteners have the same thread pitch as UNC (except for 1/2W) they may not be interchangeable.
The depth of an UNC thread is a bit more than a BSW.

You may be able to put a UNC bolt into a BSW nut but a BSW bolt on a UNC nut could cause a problem.

The bolts on My Bumper overiders, are UNC, But I have BSW nuts on them just to keep the Fastener Police calm.

Jim B.
JA Benjamin

This thread was discussed between 19/09/2018 and 21/09/2018

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