1958 G9 Engine sprocket troubles

Eric · Post by **Eric** » Sun Jan 21, 2007 4:19 pm

Just in case it helps all hexagon nuts and bolts will have a dimension of some sort across the flats this does not mean they are all used with Unified Threads or A/F spanners.

To further help here are the thread diameters and max & min sizes Across the Flats and the nominal size Across the Corners for some of the larger diameter Whitworth, or BSF or I think also Cycle Thread nuts.

As the crankshaft nut is a rather large one its probably one of them. You may be able to get a good idea of size using respectable engineers steel rule if it has very small increments marked. I will leave you to work out the nearest equivalents to 1/64”, 1/32” 1/16” 1/8” etc.

½” Dia - max AF 0.820” min AF 0.812” Nominal AC 0.95”

9/16” Dia - max AF 0.920” min AF 0.912” Nominal AC 1.06”

5/8” Dia - max AF 1.010” min AF 1.000” Nominal AC 1.17”

¾” Dia - max AF 1.200” min AF 1.190” Nominal AC 1.39”

7/8” Dia - max AF 1.300” min AF 1.288” Nominal AC 1.50”

1” Dia - max AF 1.480” min AF 1.468” Nominal AC 1.71”

1 1/8” Dia - max AF 1.670” min AF 1.658” Nominal AC 1.93”

1 1/4” Dia - max AF 1.860” min AF 1.845” Nominal AC 2.15”

The strange thing is the book does actually say use a ring spanner. Perhaps this will inflict less distortion upon the nut as it is also the flap valve for crankcase breathing.
Edited by - Eric on 21 Jan 2007 4:26:46 PM

Simonn · Post by **Simonn** » Sun Jan 21, 2007 6:29 pm

Good news - I managed to get it off - I used a 36mm impact socket on the air impact driver and when that didn't seem to be working put a long extension on it an it just slipped off. A little burring on the nut edges but nothing to worry about.

Didn't have to resort to the broom!

Thanks for all the help

Simonn

Eric · Post by **Eric** » Sun Jan 21, 2007 11:03 pm

36mm would be 1.417" so you were lucky not to take all the corners off the nut because it must be a 1" Whitworth that would be 1.480" / 1.468". Still its all well that ends well, but do try to find at least a full set of Whitworth open ended spanners and a set of sockets.

Auto jumbles are good hunting grounds and remember some of the old rusty looking tools could be the best. Shiney new stuff from far off shores at apparently bargain basement prices is probably the most expensive way of buying them, because you will ruin so many fastners and you end up throwing the spanners away. I purchased a set of old/new stock from a traditional tool merchant some years ago, they are open ended of the black finish type and they are very good spanners. I also have a full set of ring spanners, sockets and another part set of Whitworth open ended, they are a part set because I loaned some elsewhere many years ago and that was the last I saw of them. So remember to hang onto your nuts, by hanging on to your spanners.For those over the pond for spanners read wrenches.Edited by - Eric on 21 Jan 2007 11:14:16 PM

Charles · Post by **Charles** » Mon Jan 22, 2007 9:35 am

A point to bear in mind is that the 'wedge' method means any damage to chain or sprocket is visible and accessible. The broomstick method through the spokes means all the pressure you apply is transmitted through one tooth of a gearbox cog or two, something much harder to fix if it breaks.

itma · Post by **itma** » Mon Jan 22, 2007 10:20 am

The broom handle will break before anything else does, thats why I say broom handle, I could have said a lump of 4x2, or a fork stanchion, or a scaffold pole; there is method in my insanity.
Fortunate that that impact driver did`nt take the corners off, that would have been interesting.Of all the crimes committed upon old machinery, I find the use of metric tools on whitworth items the most appalling
"There is no god but whitworth"
Masses of surplus whitworth spanners about, ex MOD and the like, and as Eric says boot sales are a good source, as is Itma who has boxes of them for sale
yes this is an advert Mick!!!

Simonn · Post by **Simonn** » Mon Jan 22, 2007 10:12 pm

The hunt is on for a set of bigger spanners!

Eric · Post by **Eric** » Mon Jan 22, 2007 11:35 pm

Mick its not completly wrong to use metric spanners upon Whitworth nuts and bolts. As with many things there are some metric ones that will actually fit just just as well as the correct ones, because the metric sizes happen to fall within the same tolerance band as the Imperial sizes. I remember this because I did once many years ago work for a company that made car wheel braces and I did an excercise to work out how many new sets of forging tools we would have to make when metrication took over. I dont remember the answers but I know there were some that were basically the same or so simlar as to make no significant difference.