DIY AoM/Rocking Conversion Bushings? (Update)

[Danley]

Anyone ever drill out stock Adjust-O-Matic bushings to the point where the bridge cups can fit within them? Really - it seems you could even cut the bushings short to avoid having to drill straight all the way through, just leaving the uppermost part, on which the bridge cup could rest flush. Seems like there should be enough metal to do this. Thoughts?

[timtam]

If I understand what you're suggesting, these are the parameters: thimble external diameter is ~9mm, and most AOMs have M8 (8mm) threaded posts. So you're talking about a 9mm bit drilling out ~1mm. Might be worth a try on a cheap set of AOM/TOM M8 bushings.
Thimble (0054447049) diameter specs ..
https://www.guitarpartsresource.com/gbridge_jagjazz.htm

However, if it's on a guitar with a closer trem, which has been commonly combined with the AOM by Fender (eg CP, Squier JMJM), I've been thinking recently about a potential issue with that. The closer trem means that the string angle is sharper over the back of the bridge. That will create a resultant string force on the bridge that is no longer near to directly downwards (as with a conventional trem placement), but instead is now directed rather more forward. A fixed bridge like an AOM should be able to resist that force (although its high friction saddles are problematic for other reasons). But a rocking bridge will be pushed forwards over time by that forward force. It will have a hard time returning to a neutral, centralized position after trem use. So attempting to switch out an AOM for a rocking bridge on a guitar that also has the closer trem might not be such a good idea. The same argument would apply to a Buzzstop with a rocking bridge. The only guitar I can think of that Fender has put a closer trem and rocking bridge on is the Player series (HH) JM.

[Danley]

AOM mounts on order

Good thoughts on the closer trem - I think it'd be helpful to hear from someone who used the Staytrem conversion bushings for this purpose since I think most of those wound up on a CP or Mascis. I actually have had a Telecaster I modified to take the rocking bridge/vibrato mounted about an inch closer to the bridge (though still not as close as on a CP/Mascis.) No issues with that guitar, the bridge stayed/stays rock solid centered (I'm actually disassembling it to use the parts on this Mascis project.)

[alexpigment]

But a rocking bridge will be pushed forwards over time by that forward force. It will have a hard time returning to a neutral, centralized position after trem use. So attempting to switch out an AOM for a rocking bridge on a guitar that also has the closer trem might not be such a good idea.

While this is academic at this point due to their shipping policy, I have the Staytrem bridge with the conversion inserts on two of my "close trem" JMs and they don't have any problem returning to neutral. I sometimes go for weeks without tuning those guitars, even with regular trem use. My various experiments with DIY options have been less than optimal - although pretty good (trem down is no issue, trem up is sometimes a problem). So it *is* possible to have no problems with the bridge returning to neutral with the closer trem spacing, but apparently it takes the Brits to do it right

[Danley]

But a rocking bridge will be pushed forwards over time by that forward force. It will have a hard time returning to a neutral, centralized position after trem use. So attempting to switch out an AOM for a rocking bridge on a guitar that also has the closer trem might not be such a good idea.

While this is academic at this point due to their shipping policy, I have the Staytrem bridge with the conversion inserts on two of my "close trem" JMs and they don't have any problem returning to neutral. I sometimes go for weeks without tuning those guitars, even with regular trem use. My various experiments with DIY options have been less than optimal - although pretty good (trem down is no issue, trem up is sometimes a problem). So it *is* possible to have no problems with the bridge returning to neutral with the closer trem spacing, but apparently it takes the Brits to do it right

Curious to hear what you've tried DIY - Believe I will need to drill the AOM bushings so the tolerance is *tight* with the Jazzmaster cups as possible, and possibly use loctite to make the AOM bushings/rocking cups act close to 'one piece.'

[timtam]

Curious to hear what you've tried DIY - Believe I will need to drill the AOM bushings so the tolerance is *tight* with the Jazzmaster cups as possible, and possibly use loctite to make the AOM bushings/rocking cups act close to 'one piece.'

The other DIY options that have been reported in OSG are the upside-down, cupped/conical button grub screws, to mimic the bottom of a conventional thimble in the bottom of the AOM bushing ...
http://www.offsetguitars.com/forums/vie ... 8#p1574786
... and the drilled-out vintage-style bridge sitting on top of the AOM top posts (although it's still sitting on a fixed bridge post, so not designed to rock, it can't help but do so to some extent, not necessarily in a good way)
http://www.offsetguitars.com/forums/vie ... hp?t=33498

Re the first of these options, the ID of a conventional thimble is ~8.3mm, so with an upside-down grub screw inserted the ID of an M8 AOM threaded bushing would theoretically allow a little less range for forward-backing rocking at a given bridge height.

Re your AOM bushing drilling out mod, maybe start with an 8.5mm bit to get close to the just-less-than 9mm OD of most thimbles. And then see where you need to go from there. Starting with a 9mm bit might end up drilling out too much.

[Embenny]

Re your AOM bushing drilling out mod, maybe start with an 8.5mm bit to get close to the just-less-than 9mm OD of most thimbles. And then see where you need to go from there. Starting with a 9mm bit might end up drilling out too much.

Especially if you don't realize that your bit isn't gripped 100% straight in the chuck, causing the tip to rotate ever-so-slightly and give you a marginally wider hole in a situation where there is no tolerance for error.

I'm not speaking from experience...

[Danley]

Re your AOM bushing drilling out mod, maybe start with an 8.5mm bit to get close to the just-less-than 9mm OD of most thimbles. And then see where you need to go from there. Starting with a 9mm bit might end up drilling out too much.

Especially if you don't realize that your bit isn't gripped 100% straight in the chuck, causing the tip to rotate ever-so-slightly and give you a marginally wider hole in a situation where there is no tolerance for error.

I'm not speaking from experience...

I mentioned at the start of the thread possibly cutting the AOM bushings a bit short; I figured that may be a possible easier scenario if I need to remove smaller increments of metal using a file, without worrying as much about whether I was making the entire hole crooked. I do have several sets of bushings on order now Figure I can try it a few ways, but leaning now toward retaining the full bushing length for maximum support of the cup whatever I do, and of course using a drill press to keep it from going cock-eyed.

[Embenny]

I'll be really interested to see how this goes for you, so I can steal your idea and use it for my own benefit. Man do AOMs annoy me, but they come on so many Fenders that are orherwise such good value for the money.

[alexpigment]

Curious to hear what you've tried DIY

I did the two mods timtam mentioned above. Still have the drilled out American Pro bridge sitting around, which will fit on top of the TOM posts if you need it for any reason. I didn't like this method because the bridge stays slightly angled forward. I couldn't think of a creative way to lock it down/flat. It doesn't really have a natural resting position, so tuning issues arise. Good luck on your experiment, by the way!

[601210]

However, if it's on a guitar with a closer trem, which has been commonly combined with the AOM by Fender (eg CP, Squier JMJM), I've been thinking recently about a potential issue with that. The closer trem means that the string angle is sharper over the back of the bridge. That will create a resultant string force on the bridge that is no longer near to directly downwards (as with a conventional trem placement), but instead is now directed rather more forward. A fixed bridge like an AOM should be able to resist that force (although its high friction saddles are problematic for other reasons). But a rocking bridge will be pushed forwards over time by that forward force. It will have a hard time returning to a neutral, centralized position after trem use. So attempting to switch out an AOM for a rocking bridge on a guitar that also has the closer trem might not be such a good idea. The same argument would apply to a Buzzstop with a rocking bridge. The only guitar I can think of that Fender has put a closer trem and rocking bridge on is the Player series (HH) JM.

I haven't had an issue with a staytrem on my JMJM, it's been great. Probably more stable than my other rocking bridge guitars.

[Danley]

One down - it was slow going, since the hole I drilled wound up slightly small (intended) and I used a dremel to grind out the remainder (took longer than anticipated, but worked - need more sandpaper cylinders now to do bushing number two )

Perfect fit! Ignore how destroyed the thing looks from my vicegrips, and the leftover metal flash from the factory:




Actually ignore the crap finish I need to strip off this thing too:



Hidden Need to do the next after a trip to the hardware store...