Britbike forum Forums British Motorcycle specific Brands Triumph bulletin board Socket for gearbox sprocket nut

Good evening,
What size socket is needed to remove the gearbox sprocket nut. I know several British bike supply shops carry the tubular spanner but I wanted to know what size socket will fit. From what I can tell by taking measures and researching this nut is 1” Whitworth, not a very popular size to find. Thanks for any help you can provide.

When I was looking for that socket, the only thing I could find was made by Abingdon King Dick and it was more expensive than I wanted to pay. I bought a 1 11/16" six point socket from Tractor Supply Store and did a little work on it, lightly filing the inside flats of the socket to make it fit. The socket I found was 3/4" drive, so I also bought an adapter to fit my 1/2" drive breaker bar. I think the socket and the adapter came to less than $10. The nut came right off. I have used this socket twice now over the past 10 years, so I guess I was right to go cheap.

Hi Emlupi, What motor & transmission? There are different sizes.

For sprocket removal with main shaft in place you must have very deep socket. Problem is most deep are not deep enough.
But, if you get 3/4 drive the main shaft fits into the 3/4 square a short ways. So you just don’t push the 3/4 to 1/2 adapter all the way in.

650/750 5 speed is 1-7/8”

650 4 speed is 1-5/8”

500 I don’t know.

Bonneville Shop sells a special dual size 1/2 drive deep socket. It’s 1-7/8 with an insert to fit 1-5/8 also.
$59.95.

I have Sunex 3/4 drive deep impact socket. 6 point. Then you need a 3/4-1/2 adapter.

Shopping on line socket was about $35, adapter $10-15. Be sure it’s 3/4 drive. The 1/2 drive is too short & won’t reach nut. Even my snap-on deep was too short. Again it must be 3/4 drive so main shaft can enter into. Be careful you don’t accidentally get 1/2 drive.

Socket allows use of impact gun, but more importantly a torque wrench for tightening.

Obviously if you can weld you can cut top off one socket & weld on another or a steel tube spacer.

Kind of puts the $59.95 price of dual socket into perspective. Not a waste of $$ for what you get.
Don

Thanks for the replies, very helpful as always.

I will add: If you have a choice between a 12- point or a 6 - point socket, always go for the 6 - point one.

It will give a better grip on the nut to avoid "rounding off" the corners.

A 1/2" drive 1" socket welded on the end of a 3/4" drive socket works without any cutting.

The following photograph of such a socket, for my 1928 Ariel, illustrates this concept.



Sockets normally have faces that are somewhat rounded, so an additional feature of this socket is that I turned the face flat on the lathe so that it would engage the full depth of the thin nut. The ¾" square of the larger socket was big enough to allow the shaft to project through it, and the ½"-drive socket I welded to it was deep enough to handle the excess length of the shaft.

Conveniently, the difference in across-the-flats dimensions of "British" and "American" Fasteners becomes progressively more irrelevant as sizes increase past ~1", which makes this possible. Also, although the socket in the above photograph is 12-point, if the used-tool shop where I bought it had had a 6-point in this size, or had one been on eBay and I was willing to wait for it to be delivered, I would have bought it instead.

Ok, another question. I measured across the flats of the sprocket nut and got 1.670”. Wouldn’t a 1-11/16” (1.6875) fit this nut much better than 1-7/8” (1.875)? If not, please educate me as to what I am missing.

Yes, it would fit better. Perhaps what you're missing is what I wrote in the first line of my post, that the socket shown in the photograph is for a 1928 Ariel, not for a Triumph.

Got it. Sorry to waste your time with my inquiry.

Just to point out, Whitworth is a thread.

Yes, understood. I was going by this table which correlates Whitworth sizes to British Standard and width across the flats in inches and mm.

You need one of these:



Chris

This has come up before. I have never found the need to invest in a special socket for this job. I use a large adjustable spanner (Snail brand F spanner which was owned by my father and is about 100 years old). Brace with a length of chain on the sprocket and I have always been able to remove the nut.

Hardly a big investment: https://www.feked.com/triumph-sprocket-nut-spanner-17-8.html
I've got one for the 5 speed and another for the 4 speed, plus a combination box spanner for Norton twins. Very useful, very cheap.
I believe CBS and other US vendors can supply these.

SR

I had a little trouble finding this on the Bonneville Shop website, but here is the link to the combination deep socket that can handle both size nuts. It is 1/2" drive, so can be used with an impact or torque wrench.

https://www.thebonnevilleshop.com/p...mbo-spanner-pn-tbs-0568-61-6061-61-6125/

I plan to order one to have in my toolbox. It is basically the same price as the Sunnex and other deep sockets that don't quite work. Seems like the ideal solution to the problem, although there are plenty of other ways as everyone here has discussed.

Hi Rick, I agree 100%. That tool has value. Being able to use torque wrench removes guess work on tightening nut too. Experienced mechanics can do this by feel. Many owners may not have developed this skill yet. Funny thing at work, all the good mechanics used torque wrenches on nut like this. They’re the ones that have the best feel too.

If an owner does all their own work, actually rides bike & keeps it long term, they’ll end up buying or making almost every tool in the shop manual. It’s the cost of ownership.
Don

When I lived closer to civilization (???) there was a place called Harbor Freight that had decent tools cheap. Not stuff you would want use every day but good enough for those odd ball over size sockets that only get used occasionally. I have all the ones I need. It is a cost of ownership and will save your sanity and a bunch of rounded off nuts.

I have a 1 7/8" 1/2" drive impact socket, but I only have 5-speed boxes. Probaly not deep enough to use unless the main shaft is loose. I never could figure out how one would get enough torque on the ones which look like oversized spark plug wrenches. I think I ordered the socket and picked it up at my local Lowes for not too much $.
I don't think the HF sells anything this big unless it's part of a 3/4" socket set.
I've also found a lot of big sockets at the local flea market, really cheap. I found a 1 1/4" offset wrench which is perfect for the big nut on a Trident clutch mechanism for $5.

I have a 48mm deep well 6 ponit impact socket for 4WD front spindle nuts. I either bought it Amazon or local chain auto parts store. Does the job.

Good discussion. I will be needing to tighten this nut on my project bike relatively soon. Thanks!

any industrial supply store will have large sockets individually in whatever size you need.

I just bought and installed a complete new 5 speed transmission in my ‘74 T150V Trident. The replacement transmission is of recent manufacture bought from a large UK vendor. When I went to tighten the gearbox sprocket nut, my 1-7/16” socket was a sloppy fit on the new nut. I took the new nut with me and went tool shopping. The local Harbor Freight doesn’t sell individual sockets that size. Fortunately the Menards store (a regional big box home improvement store) across the highway from Harbor Freight had a selection of individual 3/4” drive sockets. The nut for the new transmission is 1-13/16”, not 1-7/16”. I also tried metric sized sockets without success.

The original nuts are 1-7/16”, the newest ones sold to me as part of a complete transmission were are different at 1-13/16”. Everything else was the same.

(FYI - With the strong US dollar and weak UK Pound, I was able to buy the complete transmission set from England for nearly the same money as my ruined main shaft and two pairs of replacement gears would have cost me in the US. And it was here in about a week.)

HTH, Ken

That's odd. I replaced the high gear on my '72 T120V with one from Williams. I used the old nut and it fit fine. I can't see why they would change the AF size on the nut.