View Poll Results: 1st Build Floater Suggestions
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KA Handwound 12-pole PAF humbucker
15 60.00% -
Zoller AZ-48
5 20.00% -
Biltoft Dual Blade Humbucker
5 20.00%
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Originally Posted by sbeishline
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12-02-2019 01:26 PM
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Originally Posted by Matt Cushman
How does the protrusion amount work for the straight joint?
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I am not exactly sure how to set the bridge height with a tapered mortise. With less neck angle 4% the bridge will be a bit lower than with a 4.5% angle with the 15" body it is a bit difficult to predict.
You are going to have to check your neck angle before adding your extension.With a straight walled mortice and tenon I always set the neck/bridge height with the fingerboard extension glued in place and the fingerboard fretted bound and attached to the neck. As long as the mortise is long enough the neck depth is set by where the underside of the neck extension meets the top plate. In order to set the neck deeper you remove wood from this area until your story pole indicates your desired bridge height of about 1".
I cut my tenon 1/2 "tall to fit in a mortise cut 9/16" deep the mortise is deeper than the tenon to alow for glue squeeze out and for access to the joint for disasembly.
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A tapered mortise’s advantage is it is always tight. A straight sliding mortise will be too tight until it is just right... or you go to far and ruin it.
On a tapered mortise you sneak up on it. You are not intended to ever bottom the tenon in the mortise. You start with the tenon too big which will mean it only slides in half way. You continue to shave it (or move the template back in the case of the O’Brien jig) and it will sit deeper and deeper in the mortise until you have it where you want it.
The comment about the heel being long enough is because that has happened to a friend of mine ;-)
I planned on 1/2” of fingerboard extension, 3” of body depth, less 1/4” of binding. In theory the bottom of the heel will line up perfectly with the top of the binding. A matching heel cap creates a seamless line from binding to heel cap. So 3-1/4” from bottom of fretboard to bottom of heal, right?
Turns out that fitting the tapered mortise to my neck angle (I use 5°) and making sure I had a least 3/4” above the top at the bride meant on this particular guitar with this particular carved top that I needed the neck to be a little bit prouder than 1/2”. With that my heel wasn’t tall enough to reach the top of the binding. I hadn’t given myself any margin for error.
That neck blank ended up in my bucket of shame (which now is three large Home Depot storage totes full of “learning opportunities”). I now make sure I have 3-3/4” of heel so I can trim off the excess.
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Originally Posted by rlrhett
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The ledge is cut after the mortise. Fit the neck and mark where the top meets the neck. Cut the rabbet there. I thickness the extension to match what I need and refine with a hand plane. Carving the mating part that follows the top contour I do with chalk and a rasp, but that’s the same regardless of the type of tenon.
At least that’s how I’ve always done it.
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Originally Posted by rlrhett
Last edited by Matt Cushman; 12-03-2019 at 09:43 AM.
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Originally Posted by rlrhettOriginally Posted by Matt Cushman
Rhett, if going with the dovetail, I'm also still a bit unclear of how I'll get the neck extension contour and dovetail to get into the right position.
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I don’t want to add to your confusion. I’m afraid I’ve muddied the waters rather than help.
A couple of clarifications: Both style tenons are dovetail. One is straight sliding dovetail and the other is tapered. Also, remember you are measuring the height above the bridge without fingerboard or frets. That will add 1/4”. Keep it at about 3/4” for now, or you might end up with a very tall bridge.
The way I do it is just as you describe. Cut the mortise in the body first. Robbie O’Brien cuts his so that the bottom of the mortise is about 1/2” from the edge, and that seems about right to me. Then cut the tenon.
Deliberately leave it a bit fat by pushing the template down. Fit the neck to the body. It should cinch tight, but will be well proud of where you need it. Take it back to the jig, move the template up a smidge, and rout away a little more. Re-fit the neck.
It should only take a couple of tries before a straight edge tells you that when tightly fitted you have a 3/4” gap at the bride location.
When satisfied, take a pencil and mark where the top meets the neck. Mark out a rabbet using a pencil and appropriate squares, straight edge etc. Using a hand saw, I then cut out the rabbet (parallel and perpendicular to the fretboard plane.) Use chisels and/or a rabbeting plane to cut this as cleanly as possible and fit an appropriately sized extension. They need to mate PERFECTLY. There is nothing more annoying than to look down as you are playing to see an ugly joint here!
Now the neck won’t sit tight in the body with the extension. Use a pencil and spacer and scribe the extension on both side, like you did to fit the braces to the top. Only about half the extension needs to mate to the top, the rest gracefully arches up away from the top. Refine the fit with chalk, CC paper, or whatever until the neck sits tight again and about half of the extension is mated to the top.
See how much time is spent in finished carpentry. This is just for the silly extension. :-)
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You should make yourself a story pole, set up for setting your bridge height. You need a straight stick the same length as your scale length with a small block that has been cut to the same height as the desired bridge height attached to one end. This will act as your straight edge so be sure it is straight and strong. You are going to be using a straight edge repeatedly and the story pole is fast with less chance for a measuring error.
Last edited by Matt Cushman; 12-04-2019 at 12:11 PM.
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The joint for the neck to neck extension is easy to see on the finished guitar. So this joint must be square to look it's best. Some kind of router set up is best for cutting clean and square joints like this one. I use a mill but a router table or something like Benedetto uses in his book is a good way to go. My hat is off to rlrhett cutting this with a saw, chisel and plane.
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Originally Posted by Matt Cushman
Originally Posted by rlrhettOriginally Posted by Matt Cushman
Next step, I’ll make the story pole. Then get to the mortise.
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As Matt and Rhett suggested, having a story stick will be necessary.
Last night, I milled a piece of leftover 2 x 4 on all 4 sides. I marked the midline on both edges of the stick and measured the distance of my scale length (24.75”) and marked it in those spots.
I then used a Festool domino mortiser depth set to 25mm one one side and 20mm on the opposite side. Using a 50mm domino, I malleted it down until it protruded 1” from the stick. Then, I cut another 50mm domino to 45mm, and tapped in into the 20mm mortise on the opposite side, which ended up protruding 3/4”.
Being that my fretboard and frets aren’t in place, I will use the 3/4” when sizing the dovetail tenon and planning for cutting the rabbet at the proper height protrusion for the fretboard extension.
Here’s a couple pics of it when holding near 15th mark:
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Using the LN101 hand plane, I planed the top and back edges flush with the sides, so it will sit flush against the top of the jig:
I slid the body up into the clamp boards on the jig, and I’m not thrilled with the way it fits.
Firstly, one of the screws for the mortise template hold-downs was too long and hitting the side of the guitar before it was flush. The other screw didn’t affect it because the cutaway is there. I took it out and hacksawed ~1/4” off and that took care of that issue:
Secondly, because of the arching of the top plate, it starts to get snug pushing upwards when there’s still ~1/4” from bring flush with the jig. So, on Saturday when back in the shop, I’ll take a couple hours and either refine the current clamp boards so there’s room for the belly (remove red area) or replace them:
I also need to make a clamp, maybe with turnbuckles, to clamp the lower bout area. Can always use some ratchet straps.. Hopefully, will get this damn dovetail cut by the end of the shop day.....?
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Got into the shop later than I’d planned and started about 3 hours behind schedule.
Knowing the arch of the body kept the clamp from having ideal contact, I started by taking off the front portion of the jig clamp, marked the lower area I had previously planned, and drilled 2 holes in the corners of the area to be removed and then cut it out on the bandsaw:
I reattached the piece with screws and retested the fit with the guitar body. We then realized part of the back plate was preventing a good fit, so I had to take the front off again to remove the back piece, and repeat the same procedure to do the cutout:
After reassembling, I inserted the body and it had a much better fit in the clamp. We got out the back plate clamping caul and contemplated using it against the back of the jig (a la Cushman), but it didn’t fit. Steve came up with the idea to put the sawhorses under with some blocks stacked underneath and padded with a towel to support from the bottom. We then used a ratcheting strap clamp around the guitar waist to hold it in place:
I tried to make sure it was flush with the top of the jig and using a centerline I had marked on the guitar body, I spent a decent amount eyeballing to make sure things looked aligned from the front. I realized there was so many planes this could be off and accepted I couldn’t really do much else except request some luck from the universe. Haha I decided to stop dragging my feet and make some sawdust. Every blog I’ve read, everyone always hesitates at this stage and are nervous because it can ruin all the time and effort put into the body, me included. I resigned myself to learning to adjust with shims or what have you when something ends up wrong.
I decided to make several passes at 1/16” each to minimize stress on the body and any chance of movement. Straight bit loaded, here’s after my first pass:
And here’s after I got to goal depth of 3/4” with the straight bit:
I then used the centering bit to ensure the guide bushing was centered and changed to the dovetail bit. I then set the bit to the full depth and made the pass:
Was anxious to take the body out and see how it looked.. see next post for images (hit upload max).
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Took the body out of the jig and had a gander:
Having not cut the dovetail tenon, I needed to forge ahead to see how things turned out.
So, I turned the jig around, clamped it to the workbench, and placed the neck in. I reinstalled the threaded rod (had to remove for the mortise as it was in the way) and reset the jig angle to 4°. I changed back to the straight bit, set the template to start with the tenon oversized, and started to take the 1/16” passes. Here’s a clip of the neck routing process:
Once I got down to about 1/16” short of 3/4”, changed to the dovetail bit, and ran it at full depth, I took at look at the neck and realized I made a mistake. I had cut the neck, marked the 15th fret location and dovetail end, but never cut the 1/4” extra distance I had on the end:
No remedy this, I set the table saw cross cut sled to 4°, set the 4” double-square to the distance to wrap around the mark, and took tiny incremental passes till I got it to the line:
Because of this mishap, I needed to go back to the straight bit to reform the rest of the tenon, and again finish with the dovetail bit at the full depth. I then started the process of fitting the tenon by moving the template upwards and taking a pass with the dovetail bit. Each time, I would check the protrusion and I stopped when it got to 5/8”. Here are some pics of the story pole at the 5/8” protrusion:
As you can see, it’s close, but not touching the top plate. I stopped at this point, but prolly need to take a little more off to get to 1/2” protrusion to get it to the top. Is this a good idea?
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I was so curious to see how the alignment came out. I came up with the idea of putting an extra jig spline into the slot and see how it lined up:
Not bad!
Here’s the view of the fit from the sides:
I think I came up a bit short on the heel, but I’ll use an end cap that gets me to the start of the back plate and have a small step:
Had to take this one:
I welcome any commentary and/or direction from the gallery!
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She's looking good
No one thinks about it much but this joint is one of the more difficult to get correct.The neck body joint must be right to stay put through the years of tension.Now your all set up so that any future builds will be much easier for you.
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Originally Posted by Matt Cushman
Onto the neck extension and fret board work. I still haven't finalized any head stock shape on cardboard yet..
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I wasn’t thrilled with the position of the story pole at the 3/4” protrusion as it was still approx. 3/16” from touching the top at the bridge. I took another pass with the router and brought the protrusion for the neck extension to just over 1/2” (that got the story pole touching the top at 3/4” above):
Next, I used a pencil and marked across the dovetail at the level where it met the top plate. I then placed a piece of masking tape along the line and used a Sharpie marker to mark the line, so it would be below the rabbet area to be removed:
I set up the dado blade on the table saw and set the fence so that it’d max the cut at 3/16” for the rabbet joint. I ensured the cross cut miter fence was set to 90° and made the passes in cutting the rabbet:
Overall, I think the cut came out pretty good:
As you can see, the extension will measure about 1/32” thicker than 1/2”:
I guess this is a tad thinner than 5/8” instructed in Benedetto book. I figured the bridge height/break over angle trumped the thickness of the extension?
Here’s a view of the dovetail in the mortise:
Not a bad session!Last edited by sbeishline; 12-22-2019 at 01:07 AM.
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At the end of that previous post’s session, I milled up a piece of mahogany for the neck extension 17/32” thick (to be flush with the neck blank surface) x 3” x 5”. Definitely feels like I’ve made some visible progress when I see this pic:
Other views:
Earlier this week, I took some time to get out the LN plane and further refine the violin-style edges to about 1/8”- hand tools don’t reach the waist curves or cutaway, so I’ll need to do those on the spindle sander. I plan to finalize those by hand:
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Been a bit since I touched the fretboard, but it was time to proceed. I had initially planned to leave the fretboard unbound, but changed my tune on that for cosmetic purposes. I have been contemplating the best order of operations between tapering/radiusing/binding/fret installation/gluing to neck. I decided to first taper the fretboard. Because I didn’t like the idea of doing the work of radiusing to shape and then gluing on a bigger binding piece and having to risk over sanding the binding edge angle, I made the call to bind before radiusing.
I like the width of my Godin Flat Five X, so I measured the fretboard width at the 5th (1.860”), 12th, and 14th frets.. I won’t bore you with the numbers. So, I first started by using a white chalk pencil to mark the centerline. I then spent time doing a bunch of math (half of widths, converting to closest decimal for marking with ruler, etc). Then I used a straight edge to do my best to closely mark the edge lines. For being precise work, it’s really hard! The thickness of the pencil even plays a part in making things challenging!:
I set the fretboard on the tapering jig and ran a practice piece cut to see how it would line up with the actual line. Came out acceptable and decided to proceed:
Well, I had the fretboard re-loaded, saw on and ready to cut, when it struck me... I hadn’t factored in the thickness of the binding!!!!
So, I turned the saw off and flipped the fretboard over to re-mark. I wrapped the fret locations around, did more math, and remarked less 3/16” (3/32” binding strips):
I reloaded the fretboard in the jig:
I had to adjust the jig after making one of the cuts to take a little more off, but overall it came out pretty good. The post-taper-prebinding 5th fret measure came out a hair wide (1.704” instead of 1.6725).
Another experience where I appreciate the skill of pro luthiers..
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When I initially milled the fretboard, I had milled a second blank at that time to the exact same dimensions. This helped, because I was able to cut ebony pieces for the binding that were exactly the same height.
I wasn’t aware of this, but my buddy Steve had just bought a jig for cutting thin strips. As long as the piece is parallel, this allows an accurate strip to be cut using the outside cut off the table saw:
I set the distance using a 3/32” set-up block, set it tight where it made it push the blade a tad to make up for my wide taper, and had at it:
Strips came out well!
Here’s a dry fit:
I cut some 1/2” plywood to use as calls, set up some clamps, and put a minimal amount of hide glue (just enough to coat the binding piece - so it minimized risk for squeeze out into the fret slot):
She’ll be in clamps till tomorrow!
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The first neck extension blank was a bit lighter in tone, so before doing the fretboard work today, I quickly milled up another scrap that was slightly closer in tone (although still lighter).
In my thoughts about glues, I decided to use TBII PVA glue for the neck extension rabbet joint. I figured that if I ever had to steam apart the dovetail, the nearby neck extension wouldn’t be weakened.
I applied the glue:
And used this setup:
The neck blank was set on a piece of wax paper (so it wouldn’t get glued to plywood) on top of some 1/2” plywood. The blank was held down by a Bessey clamp and once the extension blank was centered, we tightened the heel clamp over top. We used some blocks clamped tight by bench dog in the vice to ensure the extension blank was pushed into the rabbet. Here she stands and she’ll rest in the clamp overnight as well!
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The dado appears to have left some noticeable ridges. Did you clean that up before the glue up?
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Elias Prinz -- young talent from Munich
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