Hints and Tips - A7 Rear Hubs

John Hardy Wrote...

The major cause of half-shaft failure is badly fitting hubs and keys and I find the best way to fit these components is as follows :

Lap the hub on the shaft using valve grinding paste until the hub can be moved round the shaft steadily showing that high spots have been removed. Clean off paste and fit the hub to the shaft without the key and tighten up hard. Note the position of the nut, i.e., count the threads on the half-shaft showing and mark top flat or corner of the nut. Remove hub, fit the key and tighten up; the nut should go on the same distance as without the key. If the nut will not go on so far the hub is riding on the key and that is the cause of the failures. To remedy, file the key until the nut will go fully home. This will need several trials; file only a bit from the key each time where it has been marked.

Which prompted the following from Dave Wilcox

John,

Your contribution re halfshafts prompts me to respond for I am reminded that some years ago one Stuart Rolt gave a talk about back axles to a monthly meeting of the Pre-War Austin Seven Club. Amongst the many useful tips he suggested that the Woodruff key was in actual fact unecessary since a properly assembled hub to halfshaft was perfectly useable provided that it was tight. He validated his idea by claiming to have driven cars so prepared. Personally, I am not about to dive into the garage and whip the keys from my axle. Austins provided them and with the aforesaid proviso of proper preparation there they will stay.

On a slight tangent but still viz a viz axles, I split the axle of my 1929 chummy some 18 months ago purely to examine condition which was unknown when I bought the car. On each half shaft there was stamped a number which also appeared on the Woodruff key and the outer hub. These numbers were specific to each side and the examination confirmed that hubs keys and shafts matched. One therefore presumes that all items are original to the axle and unless this had been changed, also the car. Condition of the keyways was good so it proves the point that if looked after you don't need to fix it just have a peek every 69 years or so!!

Thanks for the stimulus
Dave Wilcox

Anther conversation went...

> Before anyone mentions lapping the outer hub onto the tapered end of the
> shaft, I must say I am very sceptical about the benefit of this. It can
> have the effect of creating a series of ridges which will prevent the
> hub from seating properly. There is a school of thought which favours
> heating the outer hub with a blow lamp (NOT to red heat), fitting it
> quickly and tightening the nut REALLY tight.

It depends what you mean by "lapping", and how much you do it. I agree that if you go mad with the grinding paste it could produce the effect that you mention. It can also cause the halfshaft to move too far into the outer hub, which means that you have to put a washer under the nut, and will make the pinion at the inner end of the shaft bind on the diff housing. However, a light grind is generally reckoned to be a Good Thing, just to remove the worst high spots. By all means heat the outer hub (evenly, to avoid distortion). The same applies to most tapers, especially the flywheel.

> To date I've been tightening the nut on a regular basis after slugging
> the outer deeper onto the taper.

This is a Very Good Idea. I am lucky that the Chummy has open centre wheels, and each time I grease the suspension I take the hub cap off, put a socket on the halfshaft nut and stand on the socket handle. If you keep doing this, you don't need to worry too much about getting the split pin back in. The other nut that should be tightened regularly is the one on the front axle eye cotter.


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