Neck shim formulae ??

wrinkleygit

need to lower the action on my mex jaguar by 0.3 MM. at the twelfth fret as there is no downward adj on the bridge a shim in the neck pocket would seem to be the answer ( neck relief is fine). I would like to get it right fist time if possible so anyone have a guide to thickness req to achieve this. Searched the forum & found many have used this method but can't find a link to shim thickness relating to amount of action drop, thanks, Mike 

stickyfiddle

If you want lower action then any shim thicker than the amount of action change you want should achieve it. A couple of layers of cornflake packet is my standard shim of choice. Just at the bridge-end of the neck pocket.

You may even need to raise the bridge after that, which is generally a good thing for Jags.

sweepy

It actually makes Bugger all difference, if the shim is too thick then you can adjust the bridge saddles and luxuriate in the feel of a fender with a little back angle on the neck

impmann

0.3mm is pretty precise.

TBH, I'd shove a single layer shim made of a piece cut from the outer packaging of d'addarrio strings (my usual source), bolt it back together and try again. If you need more than that, you can try two... but I'd advise not to put too much more in there, as you start getting gaps appearing under the neck and in my experience it all starts to feel a bit wobbly.

If you need more than that, then I'd suggest there's something wrong and we'd probably need some pics.

meltedbuzzbox

can you notice 0.3mm of difference in a guitars action?

John_A

1 piece of string packet will get you more than 0.3mm

impmann

John_A said:

1 piece of string packet will get you more than 0.3mm

Indeed!

Phil_aka_Pip

I knew a bloke who used Rizla packets and then complained that he never had enough roach ...

ICBM

Neck shim formula:

Small action reduction - one piece of business card.
Medium action reduction - one piece of cornflake packet.
Large action reduction - one piece of photographer's mounting card.

Anything more accurate than that will need to be fine-tuned with the bridge anyway.

wrinkleygit

Thanks guys, cornflake packet it is then, that should give me plenty of bridge adj to get where I want.