What size shim did Leo design?

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ChrisDesign
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What size shim did Leo design?

Post by ChrisDesign » Sun Dec 22, 2019 1:11 pm

I hear that Leo Fender designed the JM to be shimmed. What size shim did he design for?

This story has always sounded weird to me as he could have just designed the neck pocket with an angel instead. So in addition to knowing what shim size he designed for, where did this story come from?
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Re: What size shim did Leo design?

Post by timtam » Sun Dec 22, 2019 5:07 pm

I am not sure that the JM in particular was 'designed' to be angle-shimmed. And the cruder machines then may not have been capable of accurately cutting angled pockets, even if it had made sense to cut a different neck pocket for one model. Leo's manufacturing philosophies were consistent with cutting all guitars' pockets as similarly as possible.

The JM was designed though to work with the heavier gauge strings common then, ie 13+. A set of 13s that generates about 850 Newtons of string tension force, results in ~148 N of bridge downforce (~weight of 15kg) at a 10deg string break angle. A single 13 string has tension around 70 N. With a break angle of 10°, the saddle force will be ~12.3 N. At small bend angles, doubling the break angle (by angle-shimming the neck) doubles the downforce.
https://www.gitec-forum-eng.de/2019/08/ ... s-on-line/

Leo's 'tremolo' / bridge patent makes it clear that high string friction at the saddles was important to the ability of trem action to rock the bridge properly. Downforce creates that friction. Of the ~12.3N saddle downforce above, that is halved for each of the two saddle height grub screws. At a lower break angle of 6 degs (with 80N string tension), saddle screw force is down to ~4.2N, whence the reasons for rattling screws start to become obvious.
https://patents.google.com/patent/US2972923A/en

So a simple way to manipulate string break angle would have been consistent with Leo's ideas. Even with 13s, there would have been manufacturing variations that called for the common factory-inserted shims. Maybe the neck angles were measured in the factory, or a bridge that 'looked' low got a neck shim. With the unanticipated move by players to lighter string gauges (greatly reducing downforce due to string tension), the shim remained an easy way to get back sufficient saddle downforce.

My notes say that the narrow end-pocket shims used (in the CBS era) were ...
011098 = 0.010" Gray 0.254mm
011114 = 0.015" Red 0.381mm
010918 = 0.032" Black 0.813mm
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Re: What size shim did Leo design?

Post by Danley » Sun Dec 22, 2019 5:31 pm

Countering in a different way: You don’t need a shim anyway. Of all my offsets (Jaguars, Jazzmasters, Mustangs) only one of my two Mustangs requires one. I suspect they were installed as-necessary once assembled, due to whatever differences in construction tolerance for particular guitars.

If there is a guitar the requires a shim, it’s the Jaguar (which might need one to get the original mute to even fit below the bridge and rock properly.) But without the mute, it’s definitely not a requirement for all Jaguars made.
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Re: What size shim did Leo design?

Post by ChrisDesign » Sun Dec 22, 2019 9:04 pm

So converting Fender’s shims angle raise to Stew Mac’s while pocket shims:

Fender Grey = 0.254mm
Stew Mac .25 deg = 0.28mm
Fender Red = 0.381mm
Stew Mac .5 deg = 0.51mm
Fender Black = 0.813mm
Stew Mac 1 deg = 1.27mm

This isn’t the whole truth though, as the whole pocket shims have some added height to them. It looks like a Stew Mac .25 is the best starting point for dining a fender neck, despite their website claiming .5 is the best starting point.

The whole pocket shims, from any manufacturer, overcome the air gap issue with low coupling. https://www.stewmac.com/Materials_and_S ... uitar.html
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Re: What size shim did Leo design?

Post by tribi9 » Wed Dec 25, 2019 5:41 am

ChrisDesign wrote:
Sun Dec 22, 2019 1:11 pm
I hear that Leo Fender designed the JM to be shimmed. What size shim did he design for?

This story has always sounded weird to me as he could have just designed the neck pocket with an angel instead. So in addition to knowing what shim size he designed for, where did this story come from?
And what/who is your source?
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Re: What size shim did Leo design?

Post by ChrisDesign » Wed Dec 25, 2019 2:33 pm

That is my question. I have heard it repeated over the Internet but have nothing to tie to Leo.
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Re: What size shim did Leo design?

Post by oid » Wed Dec 25, 2019 4:40 pm

Leo did not design any of them specifically for shimming or any shim size, he designed them to be cheap and easy to make and setup. It did not matter if the neck pocket or heel of the neck were a tad off because of less then stellar performance from factory workers, there was fudge room, a shim could be added to make sure the guitar left the shop in playable condition. It was a cheap and simple solution. Compare that to the set neck Gibsons, if the neck angle was off, the guitar was tossed in the dumpster, they needed somewhat skilled labor and reliable and well maintained machines. Leo was all about cheap and effective, he saw the range of 'good enough' was quite wide and there was no way to please all musicians, he never strode for some idealized perfection that would alienate every musician that had different ideas of perfection. He was a pragmatist and everything he produced reflects that.

Shim it how ever you want to get it to play well with your technique. If you have no idea what size shim that should be, experiment or find a good luthier to guide you.
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Re: What size shim did Leo design?

Post by ChrisDesign » Fri Dec 27, 2019 4:01 am

Great answer!

It’s strange that Guitars now consisted the height of perfection were designed to a low price point and built with little ‘craftsmanship’.
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Re: What size shim did Leo design?

Post by oid » Sat Dec 28, 2019 3:00 am

There is plenty of craftsmanship in Fenders, Leo excelled at identifying where that craftsmanship actually contributed to a better instrument and where it was wasted, he was an accountant after all. The interesting thing is that we have Fender guitars because of the great depression, Leo was in college getting his degree in accounting when the depression hit, it was in full force when he got out and there is little need for accountants when there is a depression of that size going on. His chosen career proved futile so he went to his hobby and started a radio repair company, over time that turned into guitar amps and guitars, but he never stopped being an accountant and made sure every penny was spent as well as it could be. If you look at the Esquier/Broadcaster/Telecaster, we see it everywhere. The neck comes out of a single board only slightly wider than the heal, the bolt on neck makes fretwork and finishing easy, the back of the headstock and heal being in the same plane make fretwork easier yet, the radius around the body is small enough that it can be removed with a router in a quick, single pass. It just goes on and on, he knew how to stretch a dollar. The thing that really made it work and made his name was that the youth was rebelling against the status quo, rock and roll was born and they wanted nothing to do with the old ways, Gibson's offering essentially looked like their dad's archtop, Fender and their penny pinching created a guitar that only suggested a guitar, they were crude by comparison, noisier than Gibson's humbucker which gives you the dirt, and new, everything rock needed to piss of Dad.

Leo had the skilled workers, he just put them to work were their skills were actually needed, high school dropouts could be quickly trained to shape such a simple neck at a fraction of the cost, then the more skilled hands could take over and finish things up. This also worked as a training program for those skilled workers, the high school dropouts which showed an aptitude and attention to detail could be moved to the more skilled positions as needed. This whole thing was more or less out of necessity, Leo had no brand and was working in a new and unproven market, he had to save as many pennys as he could to have any chance against an established behemoth like Gibson.
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