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MG TD TF 1500 - XPAG XPEG Engine Fasteners

I was sent a copy of the details of all of the above by somebody some time ago, but I didn't record the source. It lists the Oil Pump to block bolts in the various lengths (which I'm about to check based on an original set in good condition removed from an XPAG) as being 6 mm x 1 mm. The pitch is correct as I've verified it using my thread gauge but the diameter does seem fractionally small. Can anyone who has an unused original set of these and a digital vernier please check the diameter; or who has used a fine metric die to clean up these threads and can confirm the diameter of these bolts? I can't use my digital vernier at present until I find my stash of batteries. My hunch is that these 6 mm oil pump bolts may actually be 6.5 mm. If so I don't want to bugger the threads on these bolts by using the 6 mm x 1 from my set of fine metric dies. The only other 6 mm die in the set is 6 mm x .75 which is definitely not the correct pitch. Cheers
Peter TD 5801
P Hehir

The list I have from the late Dave DuBois lists them as 6 - 1.

He does not list any 6.5mm bolts.

FWIW.
P G Gilvarry

Anybody able to actually measure them? I have the list. This is what I'm trying to confirm. Cheers
Peter TD 5801
P Hehir

There is more than one list, but I guess you already knew that.

P G Gilvarry

thread valleys are radiused to prevent stress cracking and the tips radiused to fit. Bolt thread OD's are slightly smaller than the bolt size.

Ray TF 2884
Ray Lee

I found a new battery for the vernier and the bolts have a shank of approximately 6 mm as you suggest and the threads are at around 5.84 to 5.9 mm. It's just the baked on crud of decades on the bolt threads that make the die appear to be undersized. I'll now proceed using the 6 x 1 mm die to clean up the threads. Thanks Ray as this was the confirmation that I was looking for. Sorted. Cheers
Peter TD 5801
P Hehir

Peter,
A thread chaser would be more suitable than a die.
Regards
Declan
Declan Burns

I used the fine metric dies and checked and rechecked the diameter Declan both before and after. No metal removed - just accumulated crud. The thread diameter hasn't altered at all. I will look into the thread chaser option though as I'm curious as to the difference between the two methods. Your post arrived this morning and I cleaned up the 6, 8 and 10 mm bolts last night. Cheers
Peter TD 5801
P Hehir

The list I have also refers to a 5 mm x 0.75 for the fan to pulley bolts. Nobody here that I've spoken to in the trade has ever heard of 5 x 0.75. I have 5 x 0.8 and 5 x 0.9 in my fine metric tap and die set, but am unable to purchase a 5 x 0.75. Can anyone confirm the correct size of these bolts please? I know what the list says, but it may be incorrect. I'm after confirmation from someone who has actually used the correct die on these bolts. I'll be checking the actual diameter and pitch later today using the digital vernier and thread gauge and will post my findings. I am aware that at one point Moss were selling the wrong sized bolts, so their information can't be relied on. I'm seeking 'hands on' feedback only. Cheers
Peter TD 5801
P Hehir

Peter,
If the thread is M5x0.75, which I cannot confirm without removing a bolt, and you need such taps, dies chasers etc, I can get them for you. They are available here no problem. The only issue is the parcel post restrictions currently imposed by USA, Oz and NZ due to the Covid-19 which I hope will be lifted soon.
https://www.gewinde-normen.de/en/iso-fine-thread-3.html
Regards
Declan
Declan Burns

Peter,
5x0.8 and 5x0.9 are not listed in the chart of Isometric fine threads. The next standard size after M5x0.75 is M5x1mm. Store the link in my post above-it is worth it's weight in gold. If anybody runs into problems sourcing obscure taps and dies just let me know as I have good sources.

Regards
Declan
Declan Burns

Peter

Cheap and effective way to make thread chasers if you have nuts of the same thread size. Using a Junior Hacksaw cut a series of longitudinal cuts through the nut threads down to the root diameter of the female thread. The trenches you create will have a cutting action and trap the debris in the male thread, just remember to clean the nut threads after every use.

This method also works with a bolt to create a female thread chaser.

G Evans

Declan I'm not up to speed on the Isometric Chart of which you speak. It is intriguing that you have a reference to the 5 mm x 0.75, as it seems to be unheard of here in Oz. The kit I have was made by NBL (BTD-01/40M) and is described as a Metric Fine, carbon steel, tap and die set. The major HSS tap and die suppliers here (Suttons)are aware of 5 mm x 0.8 as a standard and readily available fine metric tap and die. The only other information I have is that the kit was made in the 60's, they are 1" button dies and it comes with a screw pitch gauge. The gauge verifies the original 6 mm x 1 and the 10 mm x 1.5 bolts taken from an 1250 XPAG engine as being the correct pitch and my digital vernier also confirms the diameter; so it conforms to the list that I have. Yet to measure the 5 mm bolts this way though. I'll post when I have. Cheers
Peter TD 5801
P Hehir

Peter,
M8x1.25, M6x1mm and M5x0.8mm are standard Isometric coarse threads.

If you go to buy an M8, M6 or M5 bolt that is what you will find in the DIY store.
https://www.gewinde-normen.de/en/iso-coarse-thread.html

Regards
Declan
Declan Burns

Now I am confused. I'll email you the list titled XPAG/XPEG Engine Fasteners and you hopefully can make some sense of it. The diameter and pitch of the bolts shown in the first column in the list tally with the original bolts and the readings from both my kit thread gauge and the vernier. It also quotes original, Abingdon and Moss part numbers. So if it's incorrect, someone went to an awful lot of trouble just to get it wrong. Hopefully you can shed some light. Cheers
Peter TD 5801
P Hehir

Declan you have mail. Cheers
Peter TD 5801
P Hehir

I think a lot of what is at play here is the source of the fastener design in the XPAG dates back to the times of World War I and continued through the XPEG era.

Generally today's fine metric fine thread would have an M6-0.75 and M8-1.0 as 2 sizes for example.

However in the XPAG the M6 has a pitch of 1mm while the M8 also has a pitch of 1mm. M6-1.0 would fit into a metric coarse chart. Why they M6-1.0 is used in the XPAG is a mystery

There are so many standards out there today that have variations between pitch that it is hard to fathom it out.

I have used the late Dave DuBois's list extensively, it has worked for me so far, I keep a copy on the workshop wall.

The mere fact that Dave went to the effort to make this list says a lot about the man who I only got to know and talk to in the last 2 years of his life. Similarly one of the Californian contributors has done a list for the TD chassis, just think of the effort involved there, stopping to note something as putting things back together.

On oil pump bolts Tom Lange has cautioned on ensuring any "replacement" bolts are of the correct length, not a single mm longer. Advice well worth heeding.

Peter

P G Gilvarry

Peter,
I hope this clarifies it. The (Mad)metric bolts used on the engine are a mixture of fine and coarse threads.

The main sizes are nowadays defined as: :
M5x0.75mm ISO metric fine thread DIN 13-4
M6x1mm ISO metric coarse thread DIN 13-1
M8x1mm ISO metric fine thread DIN 13-5
M10x1.5mm ISO metric coarse thread DIN 13-1
M12x1.5mm ISO metric fine thread DIN 13-6

Regards
Declan
Declan Burns

Thanks Declan, that echoes Dave's list I am sure you have.

Peter
P G Gilvarry

It's a good day when you learn something new.

I had always been led to believe that the engine bolts used on the XPAG/XPEG/XPAW were fine metric with Whitworth/BSF heads (which I'd understood were simply a fine Whitworth thread). I knew that the term 'mad metric' came from the use of the thread manufacturing machinery imported into England from the Hotchkiss Machine Gun Company and so named as it was given a Whitworth/BSF head so as not to upset the English mechanics who owned sets of Whitworth spanners.

The fact that a mixture of both fine and coarse metric threads were used on the engines and gearboxes of our cars is something of a revelation to me! This has caused me to examine the contents of my tap and die set much more closely and it appears that this 40 piece set is actually a combination set, with both fine and coarse threads included. There is another 6 mm listed, 6 x 0.75, which is obviously the fine 6 mm; and another 8 mm, 8 x 1.25 which is the coarse 8 mm.

My set ranges from 3, 4, 5, 6, 7, 8, 10 and 12 mm with two pitch sizes in each. The one problem seems to be with the 5 mm, which is listed as 5 x 0.8 and 5 x 0.9. These are, I had presumed, were the fine and coarse thread. But apparently not...

5 x 0.75 is not included in the set. None of the major suppliers that I've spoken to here in Australia, including Suttons, are aware of the existence of such a size. They had only ever heard of a 5 x 0.8 which they advised is a common and readily available standard size. Does anyone know where a 1" button die in 5 mm x 0.75 can be obtained? Cheers
Peter TD 5801
P Hehir

Peter,

Declan may be your best bet, they are out there but shipping adds a lot to the cost as you know.

https://www.victornet.com/detail/RDM-5-.75-B.html

I have bought things from Declan and shipping to US is cheaper for him that shipping to Holland.

Tom Lange published this sage advice some time back.

Quote:
t lange, Maine, USA, tlange@acadia.net
For the engine I find that M6x1, 8x1 and 10x1.5 cover just about everything, and for the rest of the car I use 1/4, 5/16 and 3/8BSF. Not all taps and dies are equal; I buy a good brand from a commercial supply house or mg specialist, and am usually happy.

There are different types of taps, though: the most common are taper taps, bottoming taps and clean-out taps, each with a different purpose. Don't use a taper or bottoming tap to remove junk from threaded holes, for instance; a clean-out tap will cause less wear to the threads. I sand-blast and dull a used tap to make a clean-out tap when I can't find the correct size clean-out tap.

Tom Lange
MGT Repair
Unquote:

Peter
P G Gilvarry

I get my British taps and dies from British Tools & Fasteners. PJ


PJ Jennings

Just to add to the confusion about the fan blade bolts being 5 mm x 0.75, I just found this quote on an archived thread about fan blade bolts which directed me via a link to the following;

"Engine. This list compiled with the help of Dave DuBois.

Note: The engine and transmission are French Standard Metric (NOT ISO Metric), with Whitworth heads: 5 x 0.75 mm, 6 x 1.0 mm, 8 x 1.0 mm, 10 x 1.5 mm and 12 x 1.5 mm. reflecting their being built in the Hotchkiss Machine Gun Factory."

To further add to the confusion I have four original bolts from this location and an original fan pulley. The bolts and the pulley threaded holes aren't even close to each other. The 5 mm bolt is way too small and 6 mm appears to be too large for the tapped hole. I also have another XPAG original that I'm yet to strip and a further water pump fan pulley assembly from a Wolseley that I'm also about to disassemble. This exercise will hopefully shed a little more light. I wont be using any taps or dies on these until this mystery is solved. The quote above appears on Chris Couper's site. It does show that the bolts are supposed to be 5 mm x 0.75, BUT it clearly states that they are (NOT ISO metric). So, next questions: What is the difference between French Standard Metric and ISO Metric? Was Dave correct? Is Declan correct? Is Chris correct? Why do the tapped holes in my spare and presumably original fan pulley appear to be not even close? Does anybody have the answer? Theory is fine, but actual hands on experience is what I seek. Pics incontrovertibly proving theory are even better. Cheers
Peter TD 5801
P Hehir

Peter

I can confirm the fan blade bolts are 5 X 0.75 because I had to purchase them from Sports Parts when I assembled my TF.

I wont divulge what I paid for them.

Graeme
G Evans

Thanks Graeme. A pretty penny I suspect. Inquiries offline confirm French Metric apparently dates from very early in the 20th century, if not before and that ISO metric didn't appear until considerably later, a few decades at least. Although ISO may appear to be the same when comparing diameter and pitch, it's the angle at the peak and trough of the threads that differs. They are not the same. I have a block that's yet to be chemically cleaned so I'll test the cleaned up sump threads and see how they fit. I've also been advised to only clean original French Metric bolts using a wire brush and to make a thread chaser by sacrificing an original French Metric bolt when removing the crud from the threaded engine block holes. My 40 piece metric set I'll now put back in the cupboard. Yet to disassemble and compare the threads on the other fan pulleys. Cheers
Peter TD 5801
P Hehir

Thanks for your contributions. I have been able to source a French Metric 5 mm x 0.75 button die here in Sydney, but only in a 13/16 OD. Apparently the 1" button die isn't available here. The bottoming tap is no problem. I might try Ebay and see what pops up in French Metric. Cheers
Peter TD 5801
P Hehir

Peter

Dont know if you are across this mob.


https://www.mg-cars.org.uk/imgytr/pdf/madmetrics.pdf


Aussie $ versus English Pound may negate purchases, he certainly has a range of gear.

Graeme
G Evans

Peter,
The old French thread (SF) had the same angle (60°) in the range of threads we are discussing as modern SI and later ISO. The difference was in the root radius. There were several SF series and some were identical to SI threads.
https://www.sizes.com/tools/thread_sf.htm
So that adds more to the confusion.
If you want the M5x0.75 die, I can send it to you posted to your door for 10€ including postage. You will have to wait until Australia lifts the parcel post restrictions imposed due to the Covid-19.

Regards
Declan
Declan Burns

No Ebay hits on French Metric. Declan on this difference of the root radius, do you or anybody else believe that the ISO taps and dies can/should/shouldn't be used on the XPAG/XPEG/XPAW? Cheers
Peter TD 5801
P Hehir

Peter,
I don't see why not. You could always run off some test pieces and compare how they fit. I would think the the engine threads are probably worn by now that the difference could be negligible-especially on parts externally fitted.
Regards
Declan
Declan Burns

I may be out of line but I have to say I don’t think there is a practical or indeed sensible alternative to using modern approximations to tooling that was common nearly 100 years ago!
I would hazard an opinion that in most cases any weakening of a thread (given similar diameter, pitch, thread angle and material) caused by varying the root shape of a thread wood be more than compensated by the safety factors built in by the original design engineers.
I have always understood that the root (and crown) shapes of both male and female threads had two functions: radiused root to avoid stress concentration and truncated crown shape to provide a little clearance for dirt contamination between the two parts of the thread.
Just my thoughts,
Chris
C I Twidle

Here are some links that may be helpful to understand thread-types. The links must be copied and pasted into your browser because they contain spaces (%20) which the BBS doesn't recognize.

This chart by Dave DuBois shows details about French Standard, Fine Metric, ISO Metric, plus other fastener types.
https://www.dbraun99.com/Dave%20DuBois/Standard_Threads.pdf

Don't know if the thread angle of French Standard and Metric are the same.

For those who may not have Dave DuBois's engine fastener list, here is a link:
https://www.dbraun99.com/Dave%20DuBois/Fasteners_for_XPAG_XPEG_Engines.pdf

Link to downloadable 3,915 page PDF Machinery's Handbook, 29th Edition. Downloads fast.
https://www.vtc1.org/cms/lib/PA03000913/Centricity/Domain/21/Machinerys%20Handbook%2029th%20Edition.pdf

Lonnie
TF7211
LM Cook

Lonnie Declan answered the question about the thread angle and identified the only difference. "The old French thread (SF) had the same angle (60°) in the range of threads we are discussing as modern SI and later ISO. The difference was in the root radius." I don't disagree with your logic Chris and it does seem that ISO metric gear can be used in lieu of the rarer French Metric taps and dies; which it appears should be correctly referred to as French Standard. When I cleaned up the threads on some of the original bolts, stuff that I'd picked up from someone who was clearing out their old T Type bits and pieces, I could see that no metal was being removed.

Finding a set of French Standard metric taps and dies I imagine would be very difficult today and if they did exist they'd be very expensive. I haunt a huge second hand engineers supplier here in Sydney who has three floors of amazing stuff, but no French Standard. He has just about every other thread known to man. Lonnie I'll check out your links. Declan I can get the 5 mm x 0.75 bottoming tap and die here for $55 all up, but I'll hold off until I have the fan and pulleys mentioned above dissembled and can compare all of the threads. Cheers
Peter TD 5801
P Hehir

Lonnie I couldn't open any of the links. I copied and pasted them initially into Google but got 'Page not found' in response to all four links. I then copied your post into a word document and tried to open the links from there. Again no joy. I then copied each of the links in turn from the word document into the browser and got the same error. Any further advice would be welcomed. Cheers
Peter TD 5801
P Hehir

Peter

Delete the https:// prefix from the threads and paste the rest into your browser. This will open the pdfs.


Graeme
G Evans

Peter 55$ whether Aussie or US is very expensive. I'd love to help but with the parcel post restrictions it's a no go at the moment.
Regards
Declan
Declan Burns

$55 AU for both the tap and die is pretty good value Declan and compares favourably with the 10 Euros just for the die. $55 US would be outrageous as our dollar is in the toilet at present against both the Euro and the $US. Thanks for the offer though. Cheers
Peter TD 5801
P Hehir

Peter,

I copied and pasted the links on my computer and on my iPhone. Both worked fine.

Here are the links without the "s" after "http" as suggested by Graeme Evans. May still require copy and paste to into your browser.

http://www.dbraun99.com/Dave%20DuBois/Standard_Threads.pdf

http://www.dbraun99.com/Dave%20DuBois/Fasteners_for_XPAG_XPEG_Engines.pdf

http://www.vtc1.org/cms/lib/PA03000913/Centricity/Domain/21/Machinerys%20Handbook%2029th%20Edition.pdf


Alternatively, you can download the documents by visiting the host websites.

(1) ENGINE FASTENERS AND THREAD INFO
Open Dave Braun's site and download the thread info and the engine fastener info.
https://www.dbraun99.com/
Scroll down to "Technical Documents and Valuable Website Links"
Click: "The collection of writings by Dave DuBois"
Click these two links:
> Fasteners_for_XPAG_XPEG_Engines
> Standard_Threads
Depending on your browser and operating system, when the document opens, save the documents to your computer by one of these three methods:
a) right-click and choose "Save as"
b) click "File" on the top line menu and choose "Save"
c) click the save icon that is in a box floating over the document.


(2) MACHINERY'S HANDBOOK
Enter this into a Google Search:
Machinery's Handbook vtc1

One of the first hits will probably be a link to
Machinery's Handbookwww.vtc1.org › lib › Machinerys Handbook 29th Edition
Click the link in Google.
Save as described above.

Lonnie
TF7211
LM Cook

Just my opinion ...

Dave DuBois' list shows only one location where French Standard M5X.75 fasteners are used ... four bolts that attach the fan to the water pump pulley. I believe that rest of the French Standard fasteners are the same as Fine Metric or ISO Metric, but with WW heads.

Moss and other MG restoration suppliers sell the fan bolts -- not cheap. Moss price is $7.29 each (USD). Moss #320-120.
https://mossmotors.com/bolt-fan-blade-1

If the threads in your pulley need cleaning, then might be cheaper to purchase a bolt from Moss. Cut a gash across the threads to make a thread chaser. Less chance of double-threading the pulley with a tap.

If the threads in your fan bolts are damaged, then it's cheaper replace with new than to buy a die to repair the original ones.

Lonnie
TF7211



LM Cook

Actually Lonnie, they're not the same, as Declan has pointed out. The difference is, as he describes. "The old French thread (SF) had the same angle (60°) in the range of threads we are discussing as modern SI and later ISO. The difference was in the root radius." French Standard metric isn't the same as ISO metric. Declan is spot on with his assessment. This is backed up with my own research offline here in Oz. I'm able to either clean the threads with a tap and die - whose only difference is the root radius - or sacrifice an original French Standard nut and bolt and make a couple of thread chasers. The difference is real and quantifiable, so with respect, it isn't a matter of opinion, but of fact. The purchase of the 5 mm x 0.75 tap and die is simply so that I can compare the difference and satisfy my own curiosity. I'll end up cleaning the remaining threads using a wire brush on the bolts, as this is the least damaging approach. I'll probably end up using the home made thread chasers on the block. Once I've been through this exercise I'll write up a piece based on my own observations and will credit Declan for his contributions. Cheers
Peter TD 5801
P Hehir

The MG midget Series TD & TD Workshop Manual Torque Spanner Data on page 7 does not give torque settings for the 4 wired Flywheel Bolts or the 6 Clutch Pressure Plate Bolts. Can someone tell me what they are?
Is there a chart available for the torque settings for all the differing bolts on this car?
Thank you.
RAB Breton

Perhaps this will help.
Not from Abingdon, but I use it.
Jim B.


JA Benjamin

Also found this one from Dave DeB.

Jim B.


JA Benjamin

While on the subject of flywheel bolts can anyone post a pic of the four flywheel bolts correctly lockwired? I have great illustrations of lockwiring in general, but it would be terrific to see exactly how it was done originally. Cheers
Peter TD 5801
P Hehir

Peter
This pic shows the correct method, although, that top wire should be tighter than in the pic
I've seen them with a single wire through all the heads but normally you would only do that for an uneven number of bolts--pairs is the go and remember to do all your wire twisting in the one direction (ie-clockwise)
willy


William Revit

Thank you for the torque settings table. Dave Dubois's table lists the torque setting for the clutch pressure plate at 19 lbft. However, I was told by Tech Support at Moss Motors that these bolts should be torquesd to 32 lbft. Does anyone know which is correct?
RAB Breton

Thanks Willy. I wondered whether it was two pairs or all four. I did a fair bit of lockwiring in the 60's working on aircraft components, so I'll be able to put my lockwiring pliers to good use. Cheers
Peter TD 5801
P Hehir

There's another method where you poke both ends of the wire into the head of the bolt from 2 adjoining holes and cross them inside and poke out on the pull side of the head and then go to the next bolt , poke them in from the pull side , cross over in the head and tie off on the outside--You need thinner wire though to allow for the crossover
I prefer the other method with thicker wire
Don't forget to double over your cut off end and tuck it in to shorten it up for protection against fatigue
William Revit

This thread was discussed between 11/05/2020 and 17/05/2020

MG TD TF 1500 index

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