Help identifying Boss pedal jack socket thread size

[bordonbert]

Hi guys.  This surely must be a known point to you pedal guys here.

I have an older Boss CH-1 Super Chorus pedal which has lost a nut from one of its jack sockets.  These are Boss' "far eastern" types so don't have our standard Imperial thread sizes.  The socket has a slightly thinner nose which a standard sized socket or potentiometer nut just drops over.

It appears to have a fine thread 8mm nose on it so I would guess it would be a M8 x 0.75mm fine thread.  The usual coarse thread for M8 is a 1.25mm pitch and this is far too fine to be that.  Then there is fine at 1.0mm pitch which again does not look right.  Finally there is the 0.75mm pitch I mentioned earlier.  You can buy the "official Boss pedal replacement nuts" which would seem from the price to be hand carved out of billet platinum but the alternatives are available as simple stainless steel standard items if you just know the correct thread.

Can anyone confirm this thread or, if this is wrong, suggest what it is?

[bordonbert]

Ok, so nobody knows the answer.  After a lot of asking around online I still couldn't find anyone who knows what size these should be.  Well I can clear this up myself and it may help some other poor soul who comes across the info.

With a bit of work with a micrometer I got the outside diameter, (8.8mm), and the thread pitch, (close to 2.35mm for 3 threads).  That seemed to put it into the M9 x 0.75mm category.  Looking at the thread specs that fits exactly with a M9 fine thread which is available.  I had to dig around a bit but sourced these from an ebay seller who wasn't asking for my dog and daughter's hand for 2 nuts.  Don't go for anything "Boss Replacement".  As soon as the Boss name or the idea of a pedal or guitar is attached the price rockets.  Just buy a common or garden "M9 x 0.75mm" Half Nut (or Jam Nut) from a fastenings supplier.  The half nut marks it as the slimmer type, (only 2mm thick), which we need for the Japanese pedal and guitar sockets.  These nuts are commonly used to tighten against a full nut so it is locked or "jammed" into place.

I have attached a picture of the two nuts which are originals and the new one fitted.  You can't tell the difference and the thread is a perfect fit.  I don't have the washer in place yet but it is sitting at home base waiting so the pedal will soon be back to exactly original spec as you can see.

So there it is.  Boss pedals need M9 x 0.75mm half nuts.

[jimilee]

Thank you very much for your research, that is helpful.  Apparently this info is hard to come by.


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