How to shim... (there are so many ways...)

[EffectsGuru]

This is a how to, I have been working on guitars, and I could use some advice... yes.. I know the concept of shimming, but I am comming here with a CUP EMPTY state of mind ... I want to learn, it doesn;t matter what I know, but what you know...

Here are some questions beginners would ask...

Why do you shim a guitar?

What effects does it have on tone?

HOW do you shim a guitar?

What material do YOU use (and we all use different things..lol)

What guitars specifically (of the vintage sort) need shimming the most..

I though tthis would be a good how to...and a great way to share trade secrets, and to help those new guys learn a bit more...

[voodoochild]

This is a how to, I have been working on guitars, and I could use some advice... yes.. I know the concept of shimming, but I am comming here with a CUP EMPTY state of mind ... I want to learn, it doesn;t matter what I know, but what you know...

Here are some questions beginners would ask...

Why do you shim a guitar?

What effects does it have on tone?

HOW do you shim a guitar?

What material do YOU use (and we all use different things..lol)

What guitars specifically (of the vintage sort) need shimming the most..

I though tthis would be a good how to...and a great way to share trade secrets, and to help those new guys learn a bit more...

I have to shim bolt on necks a lot. When I first started in the repair industry I was a purest out of inexperience mostly. I would go a far as making tapered hardwood shims or rout the neck pocket so that the neck would make full contact in the pocket. Once I started to get really busy setting up a minimal of 10 guitars per day, I had to rethink my methods. It wasn't long before I went to plastic shims cut into strips for shimming necks. Then I went to the clear pickguard material with the adhesive backing which was a huge time saver. Bottom line is that I didn't notice any difference in tone when shimming the neck. The secret is having the butt end of the neck make full contact with the back wall of the neck pocket. If you think about how the vibrations resonate from the neck into the body, you will understand this. Shims underneath have no negative or measurable effect to my hearing or anyone elses for that matter. Obviously when I build guitars I will re-route the neck pocket to set the perfect angle of the neck. Only because I believe that a high quality guitar should not require shims to play correctly. On a mass produced level its a reality that you must face. And if a customer isn't willing to pay more than $60-$80 for a set-up, then you are crazy to spend hours setting the neck angle. Use plastic shims and make sure the end of the neck contacts the body and it will be as good as it gets.

[spud1950]

As to why a neck sometimes needs to be shimmed, I think this a pretty good explanation.

"Some guitars will just NOT adjust properly with the standard methods available like the bridge saddles, nut filing adjustments and the ability to set the bow (or lack thereof) of the neck itself. Adding shims to the bolt on neck may be necessary to get the guitar to play properly at all locations up and down the neck.

A nut shim acts as a spacer between the nut and neck raising and lowering the distance between all of the strings at the lower end of the guitar, starting at fret 1 and moving towards the body of the guitar.

A neck pocket shim acts as a spacer between the neck and body, changing the angle from which the neck protrudes out away from the body.

Try to imagine the strings of your guitar as a flat plane and the fret board as a parallel plane running underneath them. The angle of the top plane which contains the strings is controlled by the position of the bridge and the nut. The angle of the lower plane which is the fret board is controlled by the neck pocket of the body.

If your setup is perfect these two planes will have an equal distance between them at any point. If your guitar doesn''t look this way try adjusting the height at the bridge itself first. This will usually take care of the problem unless you find your action becoming too high or to low equally across the length of the fret board. If adjusting the height at the bridge corrects the problem but leaves you with too high or low of an action (distance between the strings and fret board) then you will need to resort to using a shim."

[EffectsGuru]

Ok, is it ok to shim not to change the angle but just to get the measurement between the 12th fret and the bottom of the low E (the Action) to a lower measurement? For example... the action will not go low enough, and I have set the neck as good as possible and the bridge on the Jazzmaster just won't let me go any lower... so it's clear that it needs one... is it ok to put the shim in between the 4 bolts so it's raised, but at an even level (NOT changing the angle, just raising to a point where the bridge can now be used effectively) also, is a nice hard business card stock ok? the most renouned fella' in my area uses instant lotto tickets, so I assume, that should be fine... just wanted to get everyone else's 2 cents, shimming is fairly new to me, I have only done it a few times, and I have always told the customers that I will readjust for free should it need it after I shim, and if they are not happy I will refund their money, (and restore the guitar to where it was before they brought it to me should that be needed)... that being said I have never had to do that...

[Dave Kerr]

You'll be able to get by with a much slimmer shim if you adjust the neck angle, placing the shim under the part of the neck closer to the bridge. I'd think less added material is better here.

[voodoochild]

Ok, is it ok to shim not to change the angle but just to get the measurement between the 12th fret and the bottom of the low E (the Action) to a lower measurement? For example... the action will not go low enough, and I have set the neck as good as possible and the bridge on the Jazzmaster just won't let me go any lower... so it's clear that it needs one... is it ok to put the shim in between the 4 bolts so it's raised, but at an even level (NOT changing the angle, just raising to a point where the bridge can now be used effectively) also, is a nice hard business card stock ok? the most renouned fella' in my area uses instant lotto tickets, so I assume, that should be fine... just wanted to get everyone else's 2 cents, shimming is fairly new to me, I have only done it a few times, and I have always told the customers that I will readjust for free should it need it after I shim, and if they are not happy I will refund their money, (and restore the guitar to where it was before they brought it to me should that be needed)... that being said I have never had to do that...

I wouldn't shim the side. You would then cause yourself to have to use nearly the same thickness of material as the amount of distance you will need to get the strings closer to the board. That could be a 1/32'' shim which is way too thick! It would require a very thin shim to reset the angle of the neck and this would make a huge difference quick.

[EffectsGuru]

The particular guitar I am referring too, had had fret work done on it (not by me) and with shimming like DAVE KERR described, I tired various thicknesses, but it had issues down in the high fret area due to the angle change, it just didn't have enough clearance, so a ended up slightly lifting it evenly (as in without changing the angle), have you had any problems doing it this way? I have not, but it's not something I normally do... the jazzmaster bridge seems to be a poor design (IMHO). I hear they were shimmed from the factory, I would like to find out specifically what they used back than, just out of curiosity, and how they were placed. Thanks for all the feedback so far... it's been helpful. I want to establish good habits from the start, and do good work on guitars... so it's very important to me to do things correctly/in a manner that is effective.

[EffectsGuru]

I wouldn't shim the side. You would then cause yourself to have to use nearly the same thickness of material as the amount of distance you will need to get the strings closer to the board. That could be a 1/32'' shim which is way too thick! It would require a very thin shim to reset the angle of the neck and this would make a huge difference quick.

Oh, just so you know I wasn't referring to shimming the side, or just one side of the neck, but rather a piece approx. 2/3 the size of the neck pocket (square) that lifts the neck up evenly, I tried the conventional manner but due to the current fret job, it wasn't playing as nice, so, it's one of those things where I was working with what I had... but since I tried something unconventional ( as far as I know), I just wanted to get some feedback on it. When I tried to shim in the typical fashion It was fretting out in the high area of the guitar, when I lifted it evenly it resolved this... and no, the bridge couldn't fix the problem because it was as low as possible on the high "E" side ( and still too high for comfortable playing), I tried various sizes of wooden shims, and couldn't get it to stop fretting out, so, I did what I did for that reason... I hope that explains more clearly... When I tested it, I made sure that it was stable and played nice... it ended up where it should be at 3/32 and 2/32 on the low "E" and high "E" respectively (measured at the 12th fret)

[EffectsGuru]

Oh, just so you know I wasn't referring to shimming the side, or just one side of the neck, but rather a piece approx. 2/3 the size of the neck pocket (square) that lifts the neck up evenly, I tried the conventional manner but due to the current fret job, it wasn't playing as nice, so, it's one of those things where I was working with what I had... but since I tried something unconventional ( as far as I know), I just wanted to get some feedback on it. When I tried to shim in the typical fashion It was fretting out in the high area of the guitar, when I lifted it evenly it resolved this... and no, the bridge couldn't fix the problem because it was as low as possible on the high "E" side ( and still too high for comfortable playing), I tried various sizes of wooden shims, and couldn't get it to stop fretting out, so, I did what I did for that reason... I hope that explains more clearly... When I tested it, I made sure that it was stable and played nice... it ended up where it should be at 3/32 and 2/32 on the low "E" and high "E" respectively (measured at the 12th fret)

also... there was already a shim in it in the conventional manner, they were .018 thick each... I worked with them, but it always (becasue of the neck agnle) seemed to cause fret out in the higher area... he already had fret work done, but perhaps that could be the issue, again, I tried to work around it. there is more work to be done, so I can always check it out at that time and see how it has done over time... I would of coarse fix it free of charge should there be any issue...

[voodoochild]

also... there was already a shim in it in the conventional manner, they were .018 thick each... I worked with them, but it always (becasue of the neck agnle) seemed to cause fret out in the higher area... he already had fret work done, but perhaps that could be the issue, again, I tried to work around it. there is more work to be done, so I can always check it out at that time and see how it has done over time... I would of coarse fix it free of charge should there be any issue...

If shimming causes it to fret out in the higher registers then you have issues with the fingerboard. Either there is too much relief in the neck or the fingerboard has slipped and caused the end to rise.