Questions About Messy Jazz/Partsmaster I'm Trying to Upgrade

[Pavol Stromcek]

I have a rather funky JM partsmaster that I acquired in the early 90s, made from what I was told is an older pre-80s Fender body, and I'm finally embarking on a project to make it more playable, but I'm already running into some strange issues.

First, I want to swap out its plonky-sounding old Vox (or Vox style?) bridge (which doesn't match the neck radius) with a Mastery. But as I was taking measurements to determine which Mastery bridge and thimbles to get, I noticed that the bridge thimble holes in my guitar are quite shallow—only about a half inch deep, as are the non-stock thimbles. It seems the standard JM thimble hole depth is about 1 3/16"—so, quite a bit deeper. Was there ever a Jazzmaster with such shallow thimble holes? Or is it likely that the thimble holes were partially filled by whoever modded it to fit the shallower non-stock thimbles more snugly? (Or, maybe the body is not a genuine Fender, but a darn good replica?)

Either way, it looks like I will have to drill these thimble holes to the correct depth, but it seems odd that they'd be so shallow. Has anyone seen or heard of this before?

Second issue (so far) is my JM has an old tremolo tailpiece (with patent number), but no tremolo arm. I have an older arm (unknown vintage, but at least a few decades old) which is too wide to fit in the arm collar, and the tremolo arm from my Classic Vibe 70s Squier Jag is also too wide for it. I understand this is a common problem. Does anyone know a sure way of tracking down a slightly thinner trem arm that's likely to fit?

I emailed Fender via their website and the person who wrote back said the arm they have that's most likely to fit is this one: https://www.fender.com/en-US/parts/trem ... 73049.html

At any rate, I would love some advice from anyone who has encountered these particular problems.

(Once I get the bridge sorted out, I plan to replace what is an Allparts neck with a heel that's too small for the neck pocket (gap all around) with a new Fender JM neck.)

[Pavol Stromcek]

Well, I bought the tremolo arm that the Fender rep recommended, and wow—it fits! This is literally the first Fender offset tremolo arm I've ever encountered in my 30 years of owning this guitar that actually fits in this thing!

It's actually a teeny tiny bit loose—it stays in place just fine and feels quite snug when turning it, but it still seems to clank a little bit against the inside of the arm collar when gently wiggling the arm. Maybe I can look into finding a plastic or nylon bushing for it, which I've heard about.

That's one problem to check off the list.

Still puzzled by the super-shallow bridge thimble holes, though. I'll be ordering a Mastery bridge after the holiday, so I hope to be tackling that relatively soon.

[andy_tchp]

A picture might reveal a bit more about the origins of the body.

There hasn't been significant variation of the thimble hole depth from Fender-produced bodies.

[Pavol Stromcek]

If Fender didn't vary those hole depths, then I suspect that the person who put this thing together must've partially filled the holes to accommodate the shallower Vox (or Vox-style?) bridge. (But it's not an impressive bridge; wouldn't have been worth all the trouble, IMO.)

But yeah, the next time I get a moment to take this guitar apart again, I plan to take pictures to document everything, and I'll post some here.

It was repainted (white) sometime prior to my owning it, including the pickup cavities, so any dates that might have been penciled in were covered up. Guitar neck plate is non-original/non-Fender, the pots lack the markings that would indicate vintage stock, and with the neck not being original, it's difficult to date this thing. It has very nicely defined and rounded contours, though, unlike a later model I used to own, where the angles on the front (where the player's arm rests) and rear were less pronounced, but that doesn't necessarily mean much.

[Pavol Stromcek]

Below is a picture of my Jazzmaster as it currently is. It'll probably be a few weeks until I get the Mastery bridge and swap out the Vox bridge, but in the meantime I thought I'd post a photo of the guitar so you can see what I'm working with. As mentioned above, I'm pretty sure the body is pre-80s, but I have no way to accurately date it.

The plan is to first replace the very noisy Vox (or Vox style?) bridge with a Mastery. Even with the added downward tension from having the thickest and thinnest of the Stewmac neck shims in place, it's still a little buzzy. But it also doesn't even match the neck radius.

Then I plan to swap out the Allparts neck with a new Fender JM neck. The neck heel is too small for the neck pocket, with wide gaps all around. The neck itself feels fine to me, though.

Red fake tort pickguard is obviously newer, non-stock and slightly ill-fitting.

Rhythm circuit was heavily modded by the shop I bought it from back in the 90s: rollers were replaced with switches, which when engaged seem to do a bass frequency cut for both pickups. The result, interestingly, makes it sound kind of like a Strat when the pickup selector is set at the 2 and 4 positions to combine the pickups.

Pickups are black bobbin, but I have no idea how old they are; the wiring appears to have been redone. I will try to post photos of them soon. Pots appear to have been replaced at some point.

Tremolo system appears to be quite old, but has the patent number. Works fine, in any case.

[Pavol Stromcek]

OK, more photos and information here on this JM I'm desperately trying to improve.

Firstly, it appears as if the thimble holes were filled and then re-drilled to accommodate the smaller holes of the Vox bridge. But the outlines of what what appear to be the original holes look much wider than what the original holes would have been. Does it look to anyone like at some point someone drilled wider holes, then someone else came along and filled them?

The current holes are obviously too small and shallow to accommodate Mastery thimbles, so I guess I will start by widening and deepening them. I just don't know why the current holes aren't centered within the outlines you can see that suggest previously wider holes.





Here's a shot of the entire body routing. There was zero (!!!) shielding, so that's one more thing I'll need to take care of. This guitar always was on the noisy side.



Here are a couple photos of the pickups. They look like older black bobbin pickups to me, but they have been re-wound in a way that doesn't extend the wire out to the edge like it should be, like the Japanese reissue pickups. I plan to replace these at some point down the road. They sound OK, but are quieter than my Squier Jag Classic Vibe 70s stock pickups.





At any rate, if anyone has any thoughts about these thimble holes, I'd sure appreciate it. Again, I think I should be OK just widening the current holes to fit the Mastery thimbles, but the whole situation here does look a bit odd.

[Pavol Stromcek]

Continuing this little conversation with myself . . .

I noticed that these smaller thimble holes are sightly off: the edge (nearest the pickup) of the top hole measures 3/4 of an inch from the side of the bridge pickup, and the lower one is about 1/16th of an inch closer to the pickup. Sigh...

Now, I never noticed the old bridge appearing to look askew, nor did I ever encounter any problems with this in terms of function or intonation, but it sure looks like some sloppy craftsmanship on the part of the shop that I bought this guitar from a million years ago. I guess I need to determine whether I can get away with just enlarging the holes as they currently are, or if one hole needs to be shifted slightly.

In any case, can anyone tell me the distance between the bridge pickup and the thimble holes on a Jazzmaster? I'd like to try to determine which thimble hole is more accurately placed.

[Pavol Stromcek]

Man, the more measurements I make, and when I hold the Mastery bridge w/ its thimbles over the bridge area on my guitar, it's increasingly looking like I may have to dowel both of the current holes and drill new ones. The current too-small holes are spaced just a smidgen further apart than what I'd need for the Mastery, and they both seem to be a teeny tiny bit off, meaning, I can't just evenly widen one of them.

Not what I wanted to deal with, and not something I'm sure I'm even capable of dealing with. I'm very paranoid about not drilling the new holes in precisely the right place. This is my first attempt at doing anything like this, and I really don't trust myself to not screw it up!

Oh, well. I may have to leave this to a professional luthier.

Or, maybe I'll have to figure out a way to make this Vox bridge work. I suppose I could get a new neck to match the radius of the Vox bridge, and then once the Vox bridge's intonation is set, I could try slathering every loose bit of it with Loctite to try to eliminate the rattling.

I had wanted to replace the bridge first (with one that could be adjusted to match the neck's radius), then see how that improved things with the current neck still on, and then decide whether to replace the neck down the line. But now I've hit a wall here, as I may be stuck with this subpar bridge!

[GilmourD]

Man, the more measurements I make, and when I hold the Mastery bridge w/ its thimbles over the bridge area on my guitar, it's increasingly looking like I may have to dowel both of the current holes and drill new ones. The current too-small holes are spaced just a smidgen further apart than what I'd need for the Mastery, and they both seem to be a teeny tiny bit off, meaning, I can't just evenly widen one of them.

Not what I wanted to deal with, and not something I'm sure I'm even capable of dealing with. I'm very paranoid about not drilling the new holes in precisely the right place. This is my first attempt at doing anything like this, and I really don't trust myself to not screw it up!

Oh, well. I may have to leave this to a professional luthier.

Or, maybe I'll have to figure out a way to make this Vox bridge work. I suppose I could get a new neck to match the radius of the Vox bridge, and then once the Vox bridge's intonation is set, I could try slathering every loose bit of it with Loctite to try to eliminate the rattling.

I had wanted to replace the bridge first (with one that could be adjusted to match the neck's radius), then see how that improved things with the current neck still on, and then decide whether to replace the neck down the line. But now I've hit a wall here, as I may be stuck with this subpar bridge!

If you want to go professional somebody here might be able to recommend a good one local to you.

I just had a customer return a bridge because his "luthier" couldn't handle dropping grub screws into his Mascis Jazzmaster's AoM bushings as has been done by users here plenty of times with ease... I've been finding it increasingly infuriating that there are people that barely have the skills to be mediocre techs let alone the "build a whole damn guitar out of raw wood" skills of somebody deserving the title luthier.

[Pavol Stromcek]

Man, the more measurements I make, and when I hold the Mastery bridge w/ its thimbles over the bridge area on my guitar, it's increasingly looking like I may have to dowel both of the current holes and drill new ones. The current too-small holes are spaced just a smidgen further apart than what I'd need for the Mastery, and they both seem to be a teeny tiny bit off, meaning, I can't just evenly widen one of them.

Not what I wanted to deal with, and not something I'm sure I'm even capable of dealing with. I'm very paranoid about not drilling the new holes in precisely the right place. This is my first attempt at doing anything like this, and I really don't trust myself to not screw it up!

Oh, well. I may have to leave this to a professional luthier.

Or, maybe I'll have to figure out a way to make this Vox bridge work. I suppose I could get a new neck to match the radius of the Vox bridge, and then once the Vox bridge's intonation is set, I could try slathering every loose bit of it with Loctite to try to eliminate the rattling.

I had wanted to replace the bridge first (with one that could be adjusted to match the neck's radius), then see how that improved things with the current neck still on, and then decide whether to replace the neck down the line. But now I've hit a wall here, as I may be stuck with this subpar bridge!

If you want to go professional somebody here might be able to recommend a good one local to you.

I just had a customer return a bridge because his "luthier" couldn't handle dropping grub screws into his Mascis Jazzmaster's AoM bushings as has been done by users here plenty of times with ease... I've been finding it increasingly infuriating that there are people that barely have the skills to be mediocre techs let alone the "build a whole damn guitar out of raw wood" skills of somebody deserving the title luthier.

Well, I do know a few decent guitar repair shops in my area (SF Bay Area); it's just a matter of seeing how they respond when I pose this particular problem to them, and seeing how much they charge for the work.

It certainly looks doable if one has the skills and equipment, though (both of which I lack!).

[andy_tchp]

Those larger holes look like the dimensions/placement of the original thimble holes to me?

[Pavol Stromcek]

Those larger holes look like the dimensions/placement of the original thimble holes to me?

Yes, that's what I think they are—the outline from the edge of the tops of the original thimbles. Those larger marks also measure the same distance from the bridge pickup cavity, unlike the smaller holes that have been drilled within them.

I just don't understand why the smaller holes were drilled off from each other, and not more centered within those larger markings to make the bridge straight up and down/parallel to the pickups. They're just off enough from each other that I don't think I can work with them, which is why I suspect these will need to be doweled/filled and new holes drilled.

[andy_tchp]

I'm missing something. Just drill out/remove those poorly made existing plugs and press the proper Jazzmaster thimbles in?

[GilmourD]

I'm missing something. Just drill out/remove those poorly made existing plugs and press the proper Jazzmaster thimbles in?

I think the missing part might be a drill press.

It's not something I would do if I didn't have the proper tools and this is definitely something I would want to tackle with a proper, properly straight drill press.

[Pavol Stromcek]

I'm missing something. Just drill out/remove those poorly made existing plugs and press the proper Jazzmaster thimbles in?

No, it's not that simple. Those wider darker circles you see around the drilled holes are not the outlines of the holes for inserting the thimbles; they are (I believe) the outlines for the wider outer edge of the thimble tops. Does that make sense? If I drill those out and make holes that are the diameter of those wider circles, the holes would be too wide for stock or Mastery thimbles.

Maybe this is best illustrated in photos: first shows a Mastery thimble standing upright over one of the circular markings. Second shows the thimble standing upside down to illustrate how the outer edge of the top part is close to the size of the circular marking (it's actually a bit smaller than the circular marking, so another reason not to do what I believe you were suggesting).





Honestly, it kind of looks as if somebody drilled out larger holes—the same diameter as the outer edge of the original thimble tops—and then plugged them and re-drilled the smaller holes.