The Workbench

Tru-Arc (bar-bridge) Intonation Question

1

Hi everyone,

I recently acquired my dream guitar after nearly 8 years! After getting a white 5120 (which was ruined by a luthier a number of years ago) I've since upgraded to a G6118t which I'm in love with.

Onto my question... (Though I'm not sure why I'm asking, as the Tru-Arc I had on my 5120 intonated perfectly!)

Are the string grooves on a tru arc angled (which I just never noticed), to compensate for the angle the bridge is on? If not, is there a reason this isn't done? I would assume it would cause less binding potential from bigsby movement?

See included image for a quick example of what I'm talking about (though obviously not 'accurate' in terms of the actual compensated angle).

EDIT - Just realised the bridge is the wrong way around in my image example! You get the idea though

Thanks!

2

Nope, they are not angled.

In my experience, even if the bridge has to be slanted a little for intonation purposes, the strings still lay in the grooves perfectly.

3

Nope, they are not angled.

In my experience, even if the bridge has to be slanted a little for intonation purposes, the strings still lay in the grooves perfectly.

– Wildwood609

I'm not suggesting it would bind, just that it might help? (If Proteus/Tim could chime in with some thoughts, that'd be awesome!)

5

I haven't had any binding problems with the Tru-Arc . Putting the bridge at an angel has never been a problem either . But I guess will have to let the maker answer the question about why the groves are not slanted .

6

JD nails it, more or less. As soon as we started developing bridges, it was natural to think of angling the slots - taking what the machinists called a spiral cut.

The shop's machines ARE CNC, not simple lathes, but are not expensive enough to do the 4-axis cuts I'm given to understand would be needed.

I'm told the guys who own those machines would laugh at my quantities - and have absolutely zero interest in helping develop and prototype the product as my brother's shop has done. Cost would be prohibitive.

It's going too far to say the straight grooves (what the shop calls a Tootsie Roll) have never caused string buzz - I can think of maybe 10 instances in thousands of bridges - but in all but a couple there's been a fix (usually involving surgical application of needle files).

And in the waaay overwhelming majority of cases, no issues. A non-problem.

We did experiment with (and make) a model with PRESSED rather than lathed grooves, placed at an angle. That works - kinda - but doesn't look traditional, and can cause its own issues.

7

Don't take this wrong, but you're trying to fix an issue that isn't an issue.

I'm over thinking something that is a non-issue? Never! /sarcasm

And in the waaay overwhelming majority of cases, no issues. A non-problem.

As was my experience - just interesting to hear why. It all makes total sense :)

Thanks for the replies everyone!

8

It's going too far to say the straight grooves (what the shop calls a Tootsie Roll) have never caused string buzz - I can think of maybe 10 instances in thousands of bridges - but in all but a couple there's been a fix (usually involving surgical application of needle files). - Proteus

I've seen a few guitars, including my own 6128-TCG, which had a problem with string buzz or string deadening at the bridge with a Tru-Arc installed. The problem seems more common with heavier sets or those with a wound G string and arises from the string contacting the edge of the precisely-machined string slot on the front (headstock) side of the bridge.

The issue only really shows up when the bridge angle is more than a few degrees off straight and is easily solved with the round file from a set of needle files, a rotary file, or abrasive cord. Getting rid of the sharp edge of the string slot at the point of contact is usually enough to solve the contact issue without affecting the function of the bridge.

The real solution, of course, would be a SerpenTune version.

It's interesting that many are so quick to dismiss concerns about this issue. It's similar to how many reacted to the radius mismatch issue that the Tru-Arc was created to solve.

9

It's interesting that many are so quick to dismiss concerns about this issue. It's similar to how many reacted to the radius mismatch issue that the Tru-Arc was created to solve.

The tru-arc I purchased for my old 5120 (probably about 7 or 8 years ago now) didn't have this issue, and I imagine (as Proteus said) the vast majority of others do not either. Perhaps this is because that majority use 10's with a plain G? Who knows... (Personally I use D'Addario 115's)

As much as I loved the 5120 with a tru-arc, I've opted for an ABR 2400 this time around. If I don't like it, I'll be going back to the tru-arc :)

10

I use a wound g string with my tru-arc and have never had a problem.I do and have always,put a dab of graphite in the slots on the bridge and nut on my Bigsby equipped guitars.

11

can I say the serpent tone bridge is the greatest thing to happen to my Dipinto Galaxy especially after dumping the rollerskate from hell? I guess this post belongs on the GIV clown button thread.

12

I know that Tru-Arc offers a serpentine option. Does that work toward more accurate intonation? On the 5622 in particular.

14

A real salesman, ladies and gents!


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