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Sanity Check on Siting an Ashtray Bridge on a New Build - Methodology

Discussion in 'Tele-Technical' started by knockeduptele, Jan 12, 2018 at 8:31 PM.

  1. knockeduptele

    knockeduptele TDPRI Member

    36
    Dec 15, 2017
    London
    I am sure that this topic has been covered many many times before over the years and there is another current thread running that touches on elements of this that I don't want to hijack, as this is a fairly long and detailed post running in a slightly different direction.

    If I can call on the collective experience on the forum for a sanity check as there is a million years of experience here.

    I have a comparatively expensive and very one off custom body currently winging its way to me and some fairly high end boutique parts waiting to adorn it courtesy of Armadillo in Texas.

    The body is being delivered with std neck route and pick up routes but no bridge or neck holes which means I need to do the horror job of the string thru holes for the ferules - done it a couple of times before, once successfully and once really badly - given that the brass ferules that I have for it are large, there is little margin for error. Sure f I don't get it right, then I have a get out of jail by using something like the de Lisle block, but I already have a very large mass solid brass bridge going onto the guitar so don't need that additional mass and it may push it over the top.

    For the neck holes, I have what to me seems like a good solution. In the shop I have a no brand neck which I acquired on a guitar which subsequently became a donor body for another project. This neck happens to be an extremely snug fit in an on spec Tele body with the neck holes in exactly the right place. It's never going to be a player, so I have drilled the neck holes all the way through, meaning that I can clamp the neck in position and then top drill into the body for the neck holes and end up with real consistency (I have a very serious drill press with a 450mm throat). What this means is that I can then swap necks around until i find the one that is the right match for whatever direction this particular guitar takes off in.

    Now with bridge siting, I have the following elements at my disposal to bring into play. My shop neck has a very accurately marked up centre line to give me a datum on the body at that end of the animal. If the pickup routes are on spec (so much of this relies on the new body being in spec in the first place and it's not from any of the usual suspects, its something unusual that caught my eye, so there is a risk element but god bless shims and nothing beats walking round and round the bench and lots of looking before you drill!) yes so with the bridge routes I use my Stemac routing templates (route pickup cavities later) since they have accurate markings to extend that centre line down to the bridge area.

    My bridge template is a pat pend std fender ashtray with an accurately scribed centre line, so all things being good I should have established an accurate centre datum on the body.

    My scale length is measured using a 1M steel rule leaving enough adjustment. Also laying that rule on edge from nut to bride saddle on top and bottom E positions then tells me is anything is off to avoid any L/R neck shims down the line - if in doubt fix the bridge with a couple of small screws and drop a couple of strings on to check.

    So its then it's reasonably safe to fix the bridge properly with its 4 screws having established position properly. At this point I normally use shorter strap pin screws which are the correct diameter to avoid any movement but don't go full depth - gives me a tighter fix on final fix as the bridge goes on and off a lot at this stage of the build game and you want to preserve the wood as much as possible.

    So then its' deep breath time for the sting thrus.

    Now a lot has been written on how the wood grain will push the drill off even using a bench press and this is very true and is what makes this procedure go wrong. Now my observations so far are that this is almost always in the lateral direction. Drilling from the top you can achieve six holes in a straight line but the centres are way off being equi-distant and if you are using large diameter ferules with a lip then it just wont fit and will overlap effectively writing off the body.

    So my twist on this and this is effectively the crux of this post is to do the following:

    i). Using a 2.5mm drill (I think), which is the largest dia drill that will fit through the fender bridge I'm using as my template, top drill all six string holes to a very shallow depth of say a couple of mmm - just enough to bite rather than spot.

    ii) Then remove the bridge from the body and (maybe) changing to a 3mm drill bit to reduce the flex as it hits the grain, carefully top drill through the top and bottom E string holes only

    iii). Now flip the body over. If we are really lucky, we will have achieved two holes in the correct plane giving us a datum on the back for the ferules.

    iv) The twist is to now attach the template bridge to the back of the guitar using small screws through those two holes using the sting holes of the bridge to give us an exact placement of the ferrule hole cntres on the back of the guitar.

    The theory, and I have no idea if this will work, is that it should then be possible to drill through from both sides from accurately sited positions with a reduced drill flex against the grain and have the holes meet up in the middle (I said in theory!) - whether it then needs opening up to 3.5 mm, hopefully with the drill bit flexing at the right point to join the holes, to allow smooth passage of the string for string changes I don't know, but the string passage through the body is supposed to be on the ferrule at the ball end and on the front edge of the string hole on the bridge so there are no buzzy rattly bits in this part of the instrument (at least I hope it does end up as an instument!!!)

    Thoughts?


    (Apologies for the length of post)
     

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