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| Classical Action - Dry Assembly - Pre Glue up Question http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10101&t=16205 |
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| Author: | WaddyThomson [ Sun Mar 02, 2008 7:48 pm ] |
| Post subject: | Classical Action - Dry Assembly - Pre Glue up Question |
OK, my fret board is tapered and slotted. I have made my bridge(it has been sanded to fit dome of top}. I have a saddle roughed out, nut is ready to go, except for notching for strings. Measurements of fingerboard are 7mm at nut, 4.2-4.3 bass side and 5.5-5.6 treble side at 19th fret. Measuring with a straight edge, my string height at the bridge would be 11mm. At the 12th fret using a fret (with the tangs filed off) in the slot, I have about 2.5mm on the treble side and about 3.2 or 3.3 on the bass side - using a 2mm shim at the nut, sitting on the finger board - not using the nut at present for measuring purposes. What, if anything, should I do before gluing fingerboard? Is there anything that I need to check, that I have not checked? I have a fat 4mm of saddle above the edge of the bridge. Is that too much? Should I taper the board more, and lower the saddle? My guess is that I'm pretty close, and what I have now, will probably increase by about 1mm or so, at the 12th, when the strings are on, but that could be handled at the saddle. Should I do this test with a support under the tail, and weights on the shoulders to simulate string pressure? I understand about 5 lbs weight would be close to simulating string pressure. My inclination would be to go ahead, but since you guys are here, I thought I'd ask. |
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| Author: | Jim Kirby [ Mon Mar 03, 2008 6:17 am ] |
| Post subject: | Re: Classical Action - Dry Assembly - Pre Glue up Question |
Waddy - sounds generally good. Your action may be a bit on the low side for an average classical setup, and since you have 4mm of saddle above the bridge already, if it were me I'd probably taper the fretboard some more. (I have struggled with that a little - my fretboards get to be on the thin side once they get to the soundhole.) |
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| Author: | Colin S [ Mon Mar 03, 2008 7:35 am ] |
| Post subject: | Re: Classical Action - Dry Assembly - Pre Glue up Question |
Waddy, the string height at the 12th fret that I aim for is 3.175mm (0.125") at the first string and 3.56mm (0.140") at the 6th string, with string height at the bridge of about 11 or 12mm. String height above first fret of around 0.5mm for the first string and 1mm for the 6th. You'll find that the string tension will give you about 0.25mm increase at the 12th fret so allow for that. I'd make some shims of the heigth you need (fret height plus string clearance) for first and 12th fret then use these to lay out your straight edge for string height at the bridge. Looks like you may need to plane the FB at bit more. It's best to get the final work done after the FB is glued on. I like 3.5mm of saddle exposed. Colin |
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| Author: | Marc [ Mon Mar 03, 2008 8:13 am ] |
| Post subject: | Re: Classical Action - Dry Assembly - Pre Glue up Question |
As has been said, 4mm of saddle exposed may be a tad bit high for those actions, (bass side action seems a little low I use .140-145 for initial measurements). I like to have somewhere around 3mm of saddle exposed on my base side which in my case is the same as the depth of the bridge slot. But, like Colin said, you go up .25mm at the 12th under tension (maybe a little more) which will give you a compensating drop at the saddle of .5mm putting you at 3.5 mm. On a first it's probably good you are on the safer side you don't want to get it built then have to shave the bridge. Question, you said you have an 11mm string height at the bridge w/ 4mm saddle height, is your bridge 7mm? |
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| Author: | WaddyThomson [ Mon Mar 03, 2008 10:39 am ] |
| Post subject: | Re: Classical Action - Dry Assembly - Pre Glue up Question |
Thanks guys. I have looked at my numbers again, and realized that one thing I had not done, was to sand the fingerboard between the sound hole and the neck. I did that, and it probably changed the numbers a little. I was checking my photographs last night, and I may have understated my string heights. From the pictures, it appears that I have understated the measurements on the treble side. Take a look. Bass Side @ 12th Attachment: P1000673 (Large).JPG Treble Side @ 12th Attachment: P1000675 (Large).JPG It appears that I have about 2.7 to 2.8 on the treble side. Higher than I thought. It is probably even higher now since I sanded the board. Board thickness at 19 is now barely over 4mm and about 5.2 - 5.3 on the treble side. It will probably move my 12th fret measurements up a little higher. I'll measure again tonight. Also, 2mm at the nut may be a little high for a starting point, that would be about 1mm at the first fret. I doubt it would make much difference at the 12th though. Marc, I have not actually measured the bridge since I sanded it to the dome of the top. It was just under 8mm before sanding - 7.85 - 7.9, somewhere in there. I realize it is a little low, but didn't feel 0.10 mm would be an issue, but now it probably is about 7mm in the center. |
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| Author: | Marc [ Mon Mar 03, 2008 1:37 pm ] |
| Post subject: | Re: Classical Action - Dry Assembly - Pre Glue up Question |
Waddy, my final actions are done with the strings fretted on the first fret so when I am at the stage you are curently I use a dummy fret on fret 1 and rest my straight edge on it, this removes the nut from the equation. I use dummy frets and action shims on 12th fret then measure what the string height would be at the saddle location. 11 mm string height at saddle sounds really good, but I'm not so sure about a the combo 7mm bridge height with 4mm saddle exposed. If it were me, I would prefer more of an 8mm/3mm combo. I like to make a lot of bridges the blanks are cheap and I can make them quick. I make range of heights, varying by .5 mm, usually 8.0, 8.5, and 9.0 mm with 8.5 being the expected. When I'm done gluing on and leveling the fingerboard, then fretting, leveling, crowning, and polishing frets, I can pick one that is usually just what I want. |
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