Hello all,
I finally have some more progress to share on the TuffseT Bridge! Sorry to those who have been waiting patiently that it has taken so long - I had an old colleague from the university I worked at tackle the task of 5-axis toolpathing and he was getting on with it "off the books" as and when he could.
He assures me that the hard bit is over and any issues can now be ironed out quite rapidly - the big challenge was how to fix the saddles to the machine for the complex milling operations and getting a clean release, and from this point forward I can change dimensions here and there quite easily.
The "bad stuff" first - though I think it's all fixable!
First I need to look into the best way to affix the cylindrical posts (threaded interior) to the main body of the bridge so they don't want to turn on their axis when I tighten up the post height locking set screws and post caps (the big domed flat-head mushroom screws above the posts). I managed to get it all tightened up to test it by clamping the posts, but obviously that's not an option in context of being mounted to a guitar for height adjustment purposes.
This prototype bridge body is machined from aluminium, but we could do stainless steel next and I think that's what we'll do. The locking set screw for the saddle is leaving marks on the inside of the aluminium trough since it wants to be dialed in pretty tight, so I think I should use something harder. The bridge itself is very lightweight, perhaps too lightweight.
The best method of fixing the posts to the main body of the bridge will depend on this materials choice - there might be welding or soldering / braising options there, or I might have to use an epoxy resin bond. A ribbed flange and contact fit might be an option if I have some posts specially made, but that could be a big extra unnecessary cost.
The "floor" of the saddle slots is too high, because of where the saddle locking set screw passes through the saddle. It's very nearly correct (within 0.1mm) but just that tiny difference is meaning that the set screw is making contact with the "floor" before it locks onto the "wall" (as per the design) so the saddle is lifting slightly before tightening, which is obviously a big no-no. I'm confident after messing with it for a long time that changing the design so that the "floor" goes straight through the bottom of the bridge body will solve this problem, and probably look better as well. The only issue being that it will rob the body of some torsional stability (turning it into a kind of ladder frame), which could be solved by making the piece from stainless steel or making the bridge thicker, or both.
The interior threaded "posts" are fairly decent, but they have been threaded from each end and the threads don't precisely line up in the middle. It's crazy how difficult it has been to find decent interior threaded rod! The search continues, but these will work provided you feed the "spikes" the posts sit on in from the bottom. They can't be driven through the top. Strangely though, because the locking set screws that lock these spikes into place are so short, they will happily cross the transition from one thread to another, so it doesn't actually affect operation. I still don't like it and the search continues for better posts (and might mean having some made, hence my ruminations about engineering a flanged end). These suit my purposes for now, however, and any improved part I can find or engineer will act as an interchangeable part, so I feel like I can tackle that later.
The whole thing needs a jolly good polish since I can still see the machining marks. It's a beautiful piece, don't get me wrong, but I want these to be bright and perfect and gleaming! I need to look into how I'm going to buff them up.
Ok, on to the good stuff!
The concept seems to work brilliantly. When it's all tightened together, you can really throw the thing around, toss it on the table etc. and you will never hear a rattle, even without any string tension on it. It's totally inert, like handling a stop tailpiece! That makes me excited to get one on a guitar.
Adam (the CNC guy) tells me that with this toolpath we can make saddles from brass, steel, aluminium or titanium - or pretty much anything we want. I look forward to playing around with different materials, even mixing and matching on different strings and seeing what effect that has on the sound.
The various fixings, bolts and set screws are all precisely the right size and line up flush with the design. Notwithstanding what I said about polish and surface finish, it really looks and feels like a quality piece and I think the combination of neutral vintage lines but with some modern sophistication have resulted in a design that works visually and (from what I can tell with just the one saddle) ergonomically as well. The saddle set screws are rebated with a chamfer around the hole, and your hand will only touch smooth polished metal when playing. They're also completely invisible from a playing position.
I think the design would work aesthetically on many different guitar types, so I've been thinking hard about the possibility of making a version to retrofit Les Pauls and other models. I think it would work particularly well (even in a non-rocking variant) for guitars with trapeze tailpieces like ES330s, Epiphone Casinos and Sheratons and some '60s ES335s. The reason being that guitars with a shallow bridge break angle do not impart a strong force either downwards or longitudinally, and this means the loose thread-to-thread contact on intonation adjustment in particular can cause rattles and losses.
So my way forward as of now is to have another bridge body made, maybe a millimetre deeper and from stainless steel, and with the slot "floors" cut clear through the bridge. If that solves the lifting issue, I'll have a full set of saddles made and try it out on a Jazzmaster!
Anyway, I hope you're all well and I expect the next update will be sooner than this one was! Cheers
Dan