I just bought a wreck of a Terada TW90 (dreadnought), which is considered as a very good japanese from the 70s. The guitar may need a new fretboard, and I measure the scale length to 653 mm (1st string). Can I safely buy a fretboard slotted to 650 mm, or do I need one for 653 mm?
My thought is that the extra 3mm may count for the intonation. I have measured my Blueridge BR 243 to the same scale (653mm), but is (according to what there is to find on Internet) said to have a 25 5/8" scale which actually is 650,9 mm, two mm less than the inch-scale. Distance from the nut to the 12th fret is 325mm on both guitars. I pray the play in tune.
Some of those Terada guitars are indeed very nice Japanese instruments, and you probably have one of the best of them. The Terada company made thousands of instruments per year, mostly cheap plywood models copying popular Martin and Gibson lines. However, the ones that have the model numbers beginning with TW were their top of the range models and they are all solid timber, hand-made and excellent quality. I have a TW-10 which is a D-18 copy, and it is one of the best guitars I have ever owned ($300 in a pawn shop). I have seen some called TW-90 on EBay which are brazilian rosewood and have nice inlays. Is yours like that? I would love to see some pictures.
Regarding the scale length, you are correct that the nut-to-saddle measurement will be a little bit longer than the actual scale length of the fretboard - to allow for compensation. About 3mm longer on the 1st string and 5-6 mm longer on the 6th string would be typical. However, it is a bit variable from one instrument to another. You would do better to measure the existing fingerboard from the nut to the 12th fret, and then double this. This is the scale length that the frets were cut for and a new fretboard with the same intervals should be a suitable replacement. I am assuming that it doesn’t have a zero fret (present in some Japanese guitars of that period). If it did the appropriate measurement is zero to 12th fret and ignore the bit between zero and the nut.
Thanks. My concern was the extra 3mm frm 12th to the saddle. I am used to electric guitars, and they hardly need any compensation at all. But I think that this 653 mm scale is a 650mm when it comes to a new fretboard.
This is from the former owner: https://insta.shared.to/media/B6M3Lr-nQAz He was not happy with his investment from Japan, so I got the guitar. I think the seller was too smart to actually be trusted. I think that the Ebay-ad is still to be found, but without pictures.
OK, the seller was not happy with it, but I can certainly see some redeeming features. If you got it cheap, you got a score! The Brazilian looks beautiful. Whether it is solid or laminate is another issue, but not critical. The clouding looks like humidity blush. Blush eraser might be a remedy, or you could live with it as is. The top crack is significant, but fixable. The fingerboard inlay is one of the nicest features, so it would be a shame to lose it. Are you sure it needs a new board? How good were his bridge gluing skills? I think you could really have some fun restoring this one, and end up with a keeper.
If you do replace the fingerboard it sounds like you have got the right ideas about the scale length issue.
Thhanks for your interest. Bridge seems ok. He glued it with wood glue. I regret to say that the cracks have been glued already by a "professional" who obviously had a bad day the day he glued them. I'm afraid there is not much to do except glueing new splines in them, and that is too complicated for me. The thickness of the high end of the fretboard is small, but enough for new frets. I will think abou replacing it. I will also consider to strip the laquer and make a new finish, But I'm afraid that the finish is not sensitive for chemicals, and I am afraid of treating it with heat as long as I think that the rosewood is laminate. The guitar cost me 50USD.
At $50 you are laughing! It doesn’t need to look perfect, if you can get it to play OK. My Terada has a quite thick nitrocellulose finish. If yours is similar it would be very difficult to remove it and attempt to refinish it. Mine did have a small patch of blush or delamination of the finish which I managed to repair by carefully melting/reactivating the nitro with acetone. Your blush area is much larger, but I wonder if blush remover would allow that moisture to be released? I have no experience of using it. Maybe it is best just to live with its imperfections?