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Thread: Yamaha JR1 to Octave Mandolin Conversion Questions

  1. #1

    Default Yamaha JR1 to Octave Mandolin Conversion Questions

    Hi all,

    I've seen quite a few threads on octave mandolin conversions and I have a Yamaha JR1 (21.25" scale length) that I would like to try to convert to an OM. I haven't dealt in this realm of modifying instruments before and I have quite a few questions.

    1. Do I absolutely need to narrow the neck? I don't have a problem playing a wider mandolin and this guitar isn't that wide anyways, but is thinning the neck for other reasons?

    2. How about the nut/saddle? Should I just buy a blank nut and saddle and replace the existing ones and cut my own slots for the strings? Or is there some way to use the existing ones?

    3. I've seen some ideas for putting 8 strings into the 6 holes on the bridge. Good idea or bad idea or what's the best way?

    4. As far as parts I need to order, those would include new tuning machines, maybe a nut/saddle, strings, and a tailpiece. What else am I missing?


    Just any tips for a first timer who has only really changed strings and that's about it would be greatly appreciated.

    Thanks so much!

    JD

  2. #2
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    Default Re: Yamaha JR1 to Octave Mandolin Conversion Questions

    1. You can try using the neck without narrowing it. It might suit you, it might not. You can always narrow it later if it is too cumbersome.

    2. You will almost certainly have to replace the nut. Buy an extra blank in case you mess the first one up. You will probably have to shape and slot the nut yourself-- the chances of finding a prefabricated nut that will work are slim. It might be possible to reuse the saddle, but that is only a guess since I do not have the instrument in hand.

    3. In item 4, you mention purchasing a tailpiece. If you are going to install a tailpiece, why do you need to use the holes in the bridge at all? If you do install a tailpiece, it might be necessary to reshape the back of the bridge to keep it from interfering with the strings between the tailpiece and the saddle. It could be done, though, and might be the best way to handle the conversion. Protect the top with thick cardboard if you do have to reshape the bridge.

    If you are not going to use a tailpiece, you will have a rough time spacing your strings correctly across the bridge saddle using any combination of 6 holes. In that case, the easiest solution would be to plug the four holes in the center, drill 2 new ones, and string the instrument with 2 strings in each string hole. The holes would probably have to by enlarged somewhat to make that work.

    4. Remember that you will have to install 8 strings on a peg head that was drilled for 6. You are going to have to find a way to make that work. At the minimum, you are going to have to drill holes to accommodate 2 more strings. If you are going to use a set of four-on-a plate mandolin tuners, it is likely that you will have to plug all the existing holes and redrill to accommodate the tuners that you buy. This will be difficult to do accurately with a hand drill. I would use a drill press for such a job. I would also use a reamer and tapered plugs for such a job.


    You might find that a tenor guitar with a fairly wide neck might be a better conversion candidate than a 3/4 size 6 string. But it should be possible to convert the JR-1 also.

    If you've never done this sort of work before and you're not at least an amateur carpenter or a mechanic, you might not get it right on your first try.

    You might try browsing Frank Ford's frets.com website to get some ideas of what's involved with working on instruments.
    Last edited by rcc56; Jul-12-2018 at 11:21pm.

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