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Hi Folks,

The other day I picked a TR gearbox for a good price. I have used the top cover for two experiments (which worked OK)

So yesterday I decided to take the box apart to see how these things work, They are always shrouded in mystery similar to the diff.

There are a number of special 'Churchill' tools recommended but will that stop me :blink:

I need to remove the main shaft rear race.  Today I bought, from Machine Mart, a bearing remover. It certainly looks man enough. One needs to supply two lengths of studding.

No problem I have lots of that. 

The holes in the remover are 10mm.  I have 10mm studding with a standard 1.5mm thread    But it doesn;t fit in the remover hole !!!

The threads in the holes look to have smaller. No problem I'll make a rod with 10mm x 1mm threads.  !!!  this didn't fit also.

Just to make life awkward  I have a mice MachineMart metric tap and die kit.

The 10mm die has a 1mm pitch , the tap is 10mm x 1.5mm

AND the bearing remover is 10mm x 1.25mm       aaaarrrgggghhhhh

 

Roger

 

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Ah - standards can be a minefield can't they Roger.

As I guess you are aware, but others might not be, Metric Coarse has M10 at 1.5mm pitch but Metric Fine has two choices - 1.25mm and 1mm as you have found.  There is even an extra-fine version at 0.75mm. Obviously with the tap and die someone at Machine Mart's supplier has blundered. 

And people say that Imperial threads are confusing.......

https://www.fastenerdata.co.uk/fine-thread

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Don't talk to me about BSP threads! I have been looking to replace two slotted pop up basin wastes in the en suite. I found a potentially suitable candidate and the spec gave the thread as 1.25"BSP, there was even a 'helpful' diagram with two arrows showing the thread diameter as 1.25 inches  with 11tpi (see attached).  How was I to know that this meant 1.25"BSP,  not an actual thread diameter of 1.25". I measured the thread diameter of an existing fitting as 40.4mm , or about 1.6". I then had a thought and Googled BSP thread diameters - lo and behold  1.25"BSP is actually 40.4mm or 1.6"!

Tim

150173751_nuie-chrome-push-button-basin-waste-slotted-ek303-p37158-182084_image(1).thumb.jpg.46b67d32e2cc5ee7c725ea595e0bd45d.jpg

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roger

you really need a special grooved clamp  that attaches to the bearing for removal  richard Rogers of wensum group made a complete tool from scratch if you want his details get back to me and i will send them via another source.

regards

graham

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Hi Folks,

As a follow up I contacted MachineMart Technical dept.  They were very quick to answer the phone. However they were totally clueless

They even suggested it may be 'old money' 3/8 UNF.  (or even BSF/W/P/E)  -  but its not. 

I have ordered 10mm x 1.25mm tapes and dies from TRacy Tools.

What I did find was that they sell the rods (that are usually with a kit) separately but are not in any catalogue.

Why didn;t I buy a kit - simple really - there no dimensions so you don;t know what you are buying.

 

Roger

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1 hour ago, tim hunt said:

Don't talk to me about BSP threads! I have been looking to replace two slotted pop up basin wastes in the en suite. I found a potentially suitable candidate and the spec gave the thread as 1.25"BSP, there was even a 'helpful' diagram with two arrows showing the thread diameter as 1.25 inches  with 11tpi (see attached).  How was I to know that this meant 1.25"BSP,  not an actual thread diameter of 1.25". I measured the thread diameter of an existing fitting as 40.4mm , or about 1.6". I then had a thought and Googled BSP thread diameters - lo and behold  1.25"BSP is actually 40.4mm or 1.6"!

Tim

150173751_nuie-chrome-push-button-basin-waste-slotted-ek303-p37158-182084_image(1).thumb.jpg.46b67d32e2cc5ee7c725ea595e0bd45d.jpg

 

BSP originated, I believe as a thread for gas pipe, hence, it is refered to as 'Gas thread' and shown shorthand as G*/*.

As gas pipe is measured by its bore (flow rate capability is all important with gas, so it was the bore that was important, not the OD),  the OD was never relevant.

Gas pipe can have a good heavy wall thickness, thus a G1 1/4" - 11 thread can be over 1 1/2" OD

 

John

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H Roger, usually the rear main bearing is just a tight sliding fit on the main shaft, with the mainshaft circlip removed a few well placed whacks with a copper faced mallet on the end of the shaft will get things moving, make sure the layshaft is removed first, the lay cluster dropped to the bottom of the case and the input shaft and bearing pulled out from the front, once the mainshaft has moved forward a bit, the rear bearing can gently be drifted out rearwards (couple of access slots in the case if you look closely) and off the shaft.

When you get to the third gear circlip 3 electrical screwdrivers shoved down the slots expand the circlip enough to get it off, forget Churchill, he's old hat!! 

Cheers Rob

PS   why not tap threads in your bearing puller to suit the rods you've got?  

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42 minutes ago, RogerH said:

Hi Rob,

thanks for that.  I am following the WSM so didn't consider doing any other way.

I'll have a look later on.

 

Roger

Roger - You can watch the Pete Cox gearbox seminar on the TR Register website https://www.tr-register.co.uk/past-issue/2015/08/0003/Overdrive-and-Gearbox-Overhauling-with-Pete-Cox-Moss-Europe it might give you a few tips............

Ian

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I've stripped several TRiumph boxes in the past (TR, Stag)  Only special tool I have needed was a dummy layshaft to hold the rollers in place.

Which is easily made.

Bob.

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As a finale to this madness :o

 

In this day and age if you have an item  dimensioned in milliMeters one would expect any holes to be threaded in MM.

20 years ago it would be a fair bet that it would be Unified - probably UNC

But NO - they use a bloody Victorian thread - BSW.

I have no issues over BSW, a mighty fine thread with age and experience but why today when UNC or coarse Metric is around.

I didn't even know that the Koreans knew about BSW.

So yesterday I spent £25 on metric taps and dies that I do not really need (perhaps one day) and today I bought/buying a 3/8 BSW die.

And in reality I don;t even want to take this gearbox apart - I'm just being nosy.

 

Roger

 

 

 

 

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roger

brand new american peterson pacific  grinder arrived recently  still imperial nuts and bolts , and our bloody engineers trying to beg steal&borrow my  best imperial  spanners and sockets .

graham

 

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BSF and BSW are British thread forms and worked well and was only changed to the American UNF and UNC after the war when a huge amount of tooling came over from the States to replace that lost in the war. 

         Cheers Richard

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