Monday 16 August 2021

The Last Jobs before Rebuilding

Up to this point in the project I had not made a list of jobs to be done ….simply because there was always so much to do that the list would fill a book. However, at this stage, where all that could be done with the bike in one piece at the end of the dry build and immediately before stripping it into a thousand separate parts, I made a list of outstanding jobs. Many of these are quite small but there are still a few mini projects that need attending to.

But first, the bike needs stripping. It took me 2 years to build it and 2 days to strip it and put it into boxes!



I divide the parts up into 4 boxes:

1)    Parts that need no further attention

 2)    Parts for powder coating

 3)    Parts for outsourced plating

 4)    Parts that need some further attention of some kind ….whatever that may be

I also put small pieces into plastic bags and label those that could be confused with some other part during the final build. This is particularly important for things like nuts and bolts – it may be obvious what it is at the time of dismantling but may not be so apparent when it’s time to reassemble a few weeks later.

This was the first opportunity to check the front forks in detail. The forks were only loosely assembled on the bike and the forks blades themselves appeared to be in excellent condition – no signs of damage and no rust. I expected to have to replace the spindles, because of wear, as a matter of course but one thing that I did not expect to find was this:

The main fork stem on the bottom yoke had been crudely welded in the middle and by poking around through the stem with a screwdriver and shining a light through the centre it was apparent that it had been welded all the way around and all the way through. The top section with the thread hadn’t even been attached on-centre! It is not so easy to see by eye but the stem was actually banana-shaped. The only reason that I can think of why someone would do this is because the top thread was stripped and so a top section from another set of forks was welded on to replace the original. I can’t think of any kind of accident that would do this but not also do irreparable damage to the fork girders and the frame.

…..and so to the repair.

The fork stem is 1.125” OD and a length of EN24T of this size was acquired, the thread was screwcut on the lathe and finished with a thread chaser to fit the original (and in good condition) top nut, and the bottom section was shouldered to fit inside the existing stem with a 1.5” insertion length. The centre of the new top section is bored to give an ID = 9/16” at the lower part and ID = 13/16” at the upper part. After cutting off the welded-on top section, the remaining part of the existing stem was faced off and reamed to give a uniform hole and the new top section was pressed in with a 0.0015’’ interference fit.

 After pressing in, the joint was silver soldered and 2x 3/16” pins were inserted and also silver soldered in place. You can just see the join line of silver solder and the outline of one of the pins below it.

I really don’t understand why people that do these repairs don’t make some attempt do it properly in the first place. The original stem is 1/8” wall thickness and the ID = 7/8”. Even if someone isn’t prepared to go to the trouble that I have to repair this, why not insert a 2” length of 7/8” OD tube through the middle of both sections before welding? Simple enough. At least both parts of the stem would have been in alignment.

Anyway, job done and now on to the spindles.

Not surprisingly, there was enough wear of the spindles in the girder to warrant replacement. The original spindles that I removed had already been plated (and the plating was peeling off!) and were sufficiently undersize at 0.430” (should be 7/16” = 0.4375”) to give more than enough undesirable play. The spindles that I removed were the original AJS parts fitted 90 years ago. How do I know? Well, AJS actually went to the trouble of putting their name on the bolt heads! In the picture below you can make out the AJS insignia on the flat of the hexagon.

I have also discovered in the past that these are not, in fact, bolts but spindles with a hexagon attached to make them look like bolts. On a little AJS 350 that I restored some years ago I found that the head of the “bolt” can be easily detached by inadvertently screwing it off the spindle if the spindle is seized in the girders. This is clearly a bit of production engineering economy that AJS used to avoid a lot of machining.

I have replaced girder fork spindles on many bikes in the past using EN16T round bar of the appropriate size and then put nuts and/or milled a square on the end to substitute for a hexagon bolt.

However, I haven’t replaced any spindles for a couple of years as I have been engaged in this project. In the past, I had found only one supplier, Mallard Metals, for 7/16” diameter round bar in EN16T steel, my preferred high tensile alloy steel for these parts. I also found that I had nowhere near sufficient in my “store” to make 4 new spindles and would need to buy some more. The Mallard Metals husband (Bob) and wife team would be at every autojumble in the UK and I got to know them quite well over the years. Sadly, I found that Bob died in March 2020 and Mallard Metals is no longer trading.

I then spent many fruitless hours searching for this steel but eventually stumbled across one supplier that actually stocked it. Unfortunately they are an industrial supplier (and steel manufacturer) and this meant that I had to order it in an industrial size, namely 3m lengths. The price dropped considerably for 2 lengths and so, in due course, 2x 3m lengths of 7/16” diameter EN16T arrived.

This will last me until the end of my days and should be more than sufficient to re-spindle every one of my yet-to-be-restored projects.

Unfortunately, something else came my way at the same time. If you do a Covid-19 test at home this is not what you want to see!


Having spent the last year and a half studiously avoiding this bloody disease it has eventually caught up with me. And I thought the waking-up fuzzy head was due to a little over-indulgence on the red wine the night before.

I had already had 2 AZ inoculations many months ago and it would seem that these really do work in ameliorating the symptoms. One week later and my symptoms are similar to a mild cold or very mild dose of flu. I can still manage 6 hours a day in the workshop without a problem ….so back to girder forks.

I made 4 new spindles, shown below, and these will be fitted with a pair of half-nuts as locknuts on the bolt-head end.

This is tough steel to machine and to get a good and well-fitting thread I use 2 dies; I first run a slightly worn HSS die down the thread length to remove most of the metal followed by a nearly new die to finish the thread. Trefolex cutting paste is used to lubricate the threading.

Apart from making a couple of keys – one for the crankshaft pinion for the camshaft drive and another for the clutch the metal cutting for the project is now essentially complete.


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