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| First build, fretboard gap learning http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=43634 |
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| Author: | soma_hero [ Thu Jun 12, 2014 1:06 am ] |
| Post subject: | First build, fretboard gap learning |
I'm coming to the end of my first OM build and I'm getting close to doing up the fretboard. I did my best to machine the neck angle into the soundbox, by 25' radius and then placing a spacer under the tailblock and sanding on a flat surface. I cut the opposite angle into the heel of the neck blank. I'm using a bolt on MT with furniture hardware. I used a flat UTB. I went through flossing the heel and got to a place where I'm about 1/32" above the bridge. This was with the blank fretboard resting on the neck, and now that I've radiused it I probably need a little adjusting at the heel again. However, after getting the angle at the heel correct for height above bridge, I do have a gap under the fretboard extension of about 3/64" at the soundhole. For my learning here, this means that the angle required for height above bridge doesn't match the angle I machined into the soundboard right? How do you factor in bridge height and fretboard height when you machine this angle? I followed what Hesh wrote on http://www.lenaweelutherie.info/page6/p ... age24.html and used a 1/8" spacer under the tail. He says this will introduce some "fall away" which some people prefer. Does this seem like an acceptable amount if I glue the fretboard extension to the soundboard? I bridge is between 9 and 12mm tall right now, can't recall exactly. I know Ken ceirp says don't adjust the neck angle to compensate for this gap but could I adjust down a little and shorten the height of the bridge a bit? I don't think it's yet down to the spec of 9mm according to the plan. |
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| Author: | soma_hero [ Thu Jun 12, 2014 1:26 am ] |
| Post subject: | Re: First build, fretboard gap learning |
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| Author: | Jeff Highland [ Thu Jun 12, 2014 1:32 am ] |
| Post subject: | Re: First build, fretboard gap learning |
Measure the bridge thickness. No one can give you a meaningful answer without it. |
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| Author: | soma_hero [ Thu Jun 12, 2014 2:37 am ] |
| Post subject: | Re: First build, fretboard gap learning |
word, i'll get that in the morning |
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| Author: | bluescreek [ Thu Jun 12, 2014 8:36 am ] |
| Post subject: | Re: First build, fretboard gap learning |
Actually the neck angle is most important the bridge height should be determined by the neck angle not the other way around. In most cases the perfect number for a final height of 1/2 in should be between 1/16 in to 1/8 in. 3/32 is my perfect number .094 and you can use a drill bit for a gauge at the point of the saddle. Using a straight edge off the plane of the neck measure the point at the neck joint and add .094 to that , so you establish that point. If you think ACE angle centerline then elevation ( neck joint adjustment) you will be fine. I just did a detailed post on this a few weeks ago. Once the neck angle is correct you can make some adjustments. So what is the height at the point of the saddle now ? that will determine the adjustment that is needed |
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| Author: | Tom West [ Thu Jun 12, 2014 8:44 am ] |
| Post subject: | Re: First build, fretboard gap learning |
Soma: It looks like your using a carpenter square as a straight edge. Not the best idea in my mind, not sure of their accuracy specs., but they are used for relatively rough work. Also where the neck and body meet is not at the same height, this will mess up your measurements or at least cause you extra calculations. The real trick to getting this all to come together correctly lies in how the guitar body is built. Just thought for the future with the next one. Some folks get all worked up about neck angles, one should be looking for a smooth transition from neck to body with the two on the same plane and the correct height of that plane at the bridge position. Two possible solutions to your problem if you have the correct height but still have the "V" shaped gap. A tapered wedge under the board extension or glue the extension down and then fit the top of the finger board so things work out. Good luck with the guitar, looks like it's going to be a nice one. Tom |
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| Author: | Terence Kennedy [ Thu Jun 12, 2014 9:24 am ] |
| Post subject: | Re: First build, fretboard gap learning |
1/32" above the bridge with an unfretted board is not too bad. Always better to be under than over as it is a lot easier to increase the neck angle than decrease it once the board is glued. As to the gap under the end of the fretboard, it may go down when the neck is under tension. If you are happy with your actual neck angle you can fret to around 10 or 12 so that the stiffness of the neck is dialed in and then support the headstock and put 5 or 6 lbs of weight on each shoulder of the upper bout to mimic string tension and see what the gap under the fretboard end is. It may well go down. A little drop off is OK. If excessive shim the fretboard. You can do some minor adjustments with the Fox paddle but you don't want to thin the top too much and loose strength in the upper bout.  There have been a bunch of threads on this subject recently with some good stuff. |
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| Author: | soma_hero [ Thu Jun 12, 2014 11:34 am ] |
| Post subject: | Re: First build, fretboard gap learning |
Thanks guys, I have been trying to read up on all the posts lately and they've been really helpful. I read your post john about setting the angle it was how I went about getting my angle set. I have read that putting the neck under tension can make the gap increase or decrease according to different people so that is a little confusing. I think I'll decrease the neck angle just a bit and see how the gap looks. If I want to see about putting the neck under tension, can I clamp the fretboard to the neck or do I really need to glue it first? |
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| Author: | Terence Kennedy [ Thu Jun 12, 2014 11:45 am ] |
| Post subject: | Re: First build, fretboard gap learning |
If you put tension on the neck the fretboard needs to be glued and fretted to at least 10 and the truss rod snugged up so that it will be close to the final stiffness. Otherwise the test is inaccurate. I'd get the neck angle where you want it and forget about the extension gap. If it comes down under tension great, if not shim it. A little drop off under tension is not the end of the world and is actually a good thing as the guitar settles in down the line. |
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| Author: | meddlingfool [ Thu Jun 12, 2014 2:54 pm ] |
| Post subject: | Re: First build, fretboard gap learning |
You have things exactly as I purposely build for. Fall away is built in, everything is hunkey dorey, please pass go and collect your 200$... |
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| Author: | Jeff Highland [ Thu Jun 12, 2014 3:46 pm ] |
| Post subject: | Re: First build, fretboard gap learning |
meddlingfool wrote: You have things exactly as I purposely build for. Fall away is built in, everything is hunkey dorey, please pass go and collect your 200$... Except that we still don't know whether he has taken his measurement with a 9mm or 12mm thick bridge, or if that measurement is still the same after radiussing the fretbord. If with a thick bridge, he could be approaching a string height of 16mm which is a bit high |
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| Author: | meddlingfool [ Thu Jun 12, 2014 4:01 pm ] |
| Post subject: | Re: First build, fretboard gap learning |
Point.... |
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| Author: | soma_hero [ Thu Jun 12, 2014 9:01 pm ] |
| Post subject: | Re: First build, fretboard gap learning |
Okay, I got the heel flossed a little more to lessen the angle. Now my straight edge (point taken about the accuracy of a framing square but it's the best i got) just whiskers over the bridge. There is still a gap under the fretboard and I can't honestly tell if it got any smaller. I figure now I'll fret up and glue the fretboard to the neck and then see where it all lays. Thanks for the input guys. As of now the bridge is 8.8mm or .345" thick. Fretboard radiused thickness in the middle is .256".   
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| Author: | theguitarwhisperer [ Thu Jun 12, 2014 9:28 pm ] |
| Post subject: | Re: First build, fretboard gap learning |
That gap looks to me like it simply corresponds to the fall-off you machined into the block. That's what it looks like, the fretboard falls away from the string plane after the neck joint. |
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| Author: | soma_hero [ Thu Jun 12, 2014 10:02 pm ] |
| Post subject: | Re: First build, fretboard gap learning |
I figured so, wanted to get a consensus before I put any glue on anything |
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| Author: | meddlingfool [ Fri Jun 13, 2014 12:50 am ] |
| Post subject: | Re: First build, fretboard gap learning |
Again, I think it looks just right... On my guitars I always want to see that gap under the tongue. |
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