Fluted Post Sockets for ABR Bridge

BillDL · August 2023

I have an 80s Japanese solidbody guitar with an ABR bridge of the type where the smaller diameter (about 3.8mm) threaded posts screw directly into the wood. The threaded posts have loosened slightly in the wood over the years and I decided to look for a replacement ABR or Nashville bridge with push-in threaded metal body bushings. I have discovered that the string spacing / span of this original bridge and stop tailpiece are narrower than other Tune-O-Matic bridges and tailpieces I have replaced in the past: 10.1 or maybe 10.2mm spacing and therefore 50.5 or 51mm spread (using a cheaper digital caliper). It has a 10" radius, not the normal 12", but the post spacings centre to centre seem to be pretty standard for "import" guitars at 74mm for the bridge and 82mm for the tailpiece anchor sockets. I'm having problems finding a compatible bridge that uses the Nashville type sockets.

On one of my 335 styled guitars that has a top-locking ABR bridge (OEM for Artist Guitars) the threaded posts screw into fairly narrow diameter fluted brass bushings that are pressed into the body. The reason I know this is because one of them had been pushed down too far into the drilled hole that was deeper than the bushing, so I extracted it, dropped a short piece of brass tubing down to the bottom, and reinserted the bushing with a smear of epoxy. The bushings resemble those used as anchor bushings for dual-fulcrum tremolo posts, only they are a fair bit smaller in diameter because they don't have to be much thicker than the posts. Imagine these at around 16mm long by around 5 or 5.5mm in diameter:

Image: https://tfb-user-images.eu-central-1.linodeobjects.com/20d3a26cba54fbc20c50736599f2fb1d0fc1847f9e4b7ddb79

I've never experienced a guitar with ABR posts that screw into narrow diameter straight fluted bushings like this before. All I have ever has have been threaded posts right into wood, thicker threaded posts into short "Nashville" post sockets, and the chunky Tune-O-Matic ones with 8mm internal thread diameter as used for the stop tailpieces.

I don't actually need to replace the bridge itself, I just need to try and get a tight fit for the post to body fitting. I haven't been able to find a compatible bridge with thicker threaded posts that might form new threads in the wood and stay tight. I don't currently have a pillar drill and I didn't really want to try and drill larger holes by hand, and additionally I don't want to change the aesthetics by inserting those much larger "tailpiece" type bushings, so my thought is that if I can find something that will work as much thinner bushings that can be pushed down into the already loosened holes for the threaded posts (and maybe glued) it would make for a more rigid bridge assembly. The holes bottom out at 20mm depth. I've looked on industrial fasteners websites and the nearest I can so are sleeves to convert thread diameters and screw-in bushings that have a hex or flat socket for insertion, and the internal thread diameters have been too large.

Has anybody encountered this kind of fluted press-fit body bushing for an ABR bridge?

How have others dealt with loose fitting "screwed into the wood" posts to tighten them up?

ICBM · August 2023

BillDL said:

How have others dealt with loose fitting "screwed into the wood" posts to tighten them up?

Epoxy.

BillDL · August 2023

Thanks @ICMB. ; You mean glue the threaded posts in permanently, or just put a thin film around the sides of the holes for the posts to cut their own new threads into the hardened epoxy?

Gluing permanently seems like the cheapest way with the least hassle. I suppose I should have marked the depths the posts were down into the holes before removing them, because I'll have a bit of messing about to get it set up again with the posts in the right depth before marking them, removing them, and then gluing them permanently in place.

WezV · August 2023

it's not really permanent, it will release with some heat from a soldering iron

BillDL · August 2023

Thanks @WezV ;; I was just thinking about that, and whether the heat down the post might melt the polyester lacquer around the holes.

GluedtoMusic · August 2023

If you have a hand drill you could also drill the post holes deeper and install extra long posts if you are worried about leaning, Faber makes a product but you could also use 4 mm stainless steel threaded rod if you aren't worried about the colour,

https://www.gluedtomusic.com/products/2014/faber-extra-long-15-steel-abr-1-tune-o-matic-posts-nickel-metric-mm/

BillDL · August 2023

Thanks for the suggestion @GluedtoMusic . That's actually quite a good idea, but I was a step ahead and I've just been raking through all my jars of long thin stainless steel bolts and fittings to see if I have something in the same thread pitch that would work. The body is 40mm thick and the holes are already drilled to 20mm depth, so I have some extra depth to use. I have a feeling somebody has used something to clean the guitar on a regular basis that has softened the wood in the holes, or else the posts have been in and out a number of times and it's weakened the internal thread of the wood in the holes. £24 for a couple of threaded studs is a bit more than I would want to pay, so I would prefer meantime to check out some other solutions.

Anyway, instead of frittering time away on here shouldn't you be away packing and posting my order made yesterday?

BillDL · August 2023

Thank you for the items on my order @GluedtoMusic ;

GluedtoMusic · August 2023

No worries, please post some photos of your progress if you have any

BillDL said:

Anyway, instead of frittering time away on here

I was on lunch guv, probably

Image: https://www.thefretboard.co.uk/plugins/EmojiExtender/emoji/fb/3.gif

BillDL · September 2023

Just an update @GluedtoMusic

I bought a Gotoh GE104B ABS style bridge from you but decided to just drill out the body for the 7mm diameter shallow Nashville style post anchors with 4mm internal thread. I found some M4 x 30mm stainless steel hex grub screws in my jars of nuts and bolts (no need for the 38mm Faber ones) and used them instead of the Gotoh ones that are plain ended. The extra grip of screwing 4mm posts into 3.5 or 3.8mm holes in the body and the support of the Nashville post anchors has made for very secure support for the Gotoh bridge. The 10.3mm spacing of a new generic tailpiece against the 10.4mm string spacing of the Gotoh bridge is not noticeable, and going up from 10 or 10.1mm string spacing from the original stock ABR bridge has been negligible as the strings still have adequate space from the fretboard edges. The original bridge will still fit over the new 4mm posts and the anchors for the original stop tailpiece studs are the same internal thread as the new stop tailpiece, should I ever need to revert. The only thing I had to do was file the saddle slots on the outer saddles a little deeper to lessen the 16" radius so that it better matched the roughly 12" fretboard radius.

GluedtoMusic · September 2023

Awesome, great result

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Fluted Post Sockets for ABR Bridge

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