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Baltic birch semi-hollow Jaguar

Discussion in 'Luthier's Corner' started by mnats, Mar 5, 2018.

  1. mnats

    mnats Supporting Member

    Feb 2, 2013
    I'd been wanting to do a scratch build for a while and bought some nice blanks but hadn't worked up the nerve to do much to them yet other than cut a scarf joint. When we moved into new offices at work there were some leftover sheets of Baltic birch plywood that were going to be disposed of. So I took a sheet that had not been trampled over too badly.

    Recently I pulled it out and built a desk for my study (that's the drawer for it in the picture). There were enough leftover pieces to make a bass body out of, I thought. So I decided to start there knowing that others have been down a similar path before.

    It's a semi-hollow or chambered Jaguar shape that I want to try using a piezo with, though I've hedged my bets by leaving enough material to route for mag pickups. It will have a neck pocket to fit a standard Fender neck, but I intend to make a conversion neck in medium scale if possible. If the neck is successful I'll build another one for my CIJ Fender since I was unsuccessful at replicating its sound in medium scale using Warmoth parts.

  2. It would be cool to some contouring and use a transparent finish so you could see the plies, assuming there are no voids.
    Will_White and T_Bone_TL like this.
  3. GMC


    Jan 1, 2006
    Looking nice. Birch ply makes a lot of sense for body core. It's nice and light, structurally stable, quite cheap and easy to source. Do you find it splinters easily?
  4. b3e


    Sep 5, 2017
    Warsaw, Poland
    I definitely want to hear the finished bass :)
  5. mnats

    mnats Supporting Member

    Feb 2, 2013
    I used a very cheap jig saw for the first layer with the blade that was on there from who knows when, so there was some tear out. I think it has more to do with the quality of the tools than the material itself. I cut the next layer very wide of the line then used an oscillating spindle sander to clean it up. Final layer was cut with a pattern router bit which worked very well.


    I will use a transparent finish but as for the contouring I want to carve the frame then bend the top so you won't see plies across the contour. Not so much a fan of that look - I think there was a Korean Squier that someone refinished here...

    Thanks for the comments.
    Will_White likes this.
  6. mnats

    mnats Supporting Member

    Feb 2, 2013
    While cutting plywood and MDF to make a neck pocket jig my $200 table saw, that I’ve nursed back to health more than a few times, decided to fail again. The mechanism that raises and lowers the blade uses a press-fit proprietary oval thing that fits in a groove in a shaft. The last time I used a circlip to repair it but this time I’d decided it had outlived its expected service after 17 years.


    Because I have a newish Freud 5/8” dado set that I’m reluctant to replace I was pretty much locked into buying a DeWalt. The vast majority of the locally available table saws have a 30mm arbor. I have to say that so far I have no regrets at all. It’s crazy how much I used to fight with that old machine to do simple things.

    First order of business was to build a crosscut sled that would fit the new machine. I started by taking some old decking boards that were laying around, picking the straightest looking piece and resawing it. It dawned on me that I could just remove the metal rails I’d put on the old sled and replace them with the new rails I was making. I’m kinda slow that way.

    Anyway, I’d cut them to the correct width but found they were binding due to the fact that in spite of being very flat they had a distinct bow going on the perpendicular plane. That’s when I remembered @rudy4444 's trick of using a straightedge and router.

    Not long afterward I was deciding how to attach these rails when I thought I should probably route a channel in the old sled table since it has been varnished and glue would have some trouble sticking. So I pulled out the 3/4” bit and found it had glazed over as @Bruce Johnson showed us recently. Cleaned it up using his method.


    What an amazing thing to have techniques that I learned just in the past week that made my work so much better and more accurate than it would have been before I’d read those two tips. Thanks to all who make this such an amazing place.

    Oh yeah, the new saw:

    b3e likes this.
  7. mnats

    mnats Supporting Member

    Feb 2, 2013
    I have a couple of books that show how to cut a neck pocket but each of them concentrate primarily on flat-ended necks with small radii. Neither has a complete description of cutting a Fender Jazz style pocket.

    With a half-remembered idea of someone creating a mold using poured resin I attempted this with some casting epoxy I’d bought for another project. But I greatly underestimated the liquidity of the mixture and all I created was a mess that was tedious to clean up.


    After thinking about it for a while I decided that I would simply cut a pocket jig from some MDF. I’ve seen various ways of using straightedges against the sides of the neck but since MDF is fairly cheap and since the dimensions are known I thought I’d just draw it out on a large sheet of material then once I had some accurate cuts remove what I didn’t need.


    A Jazz neck measures 2 1/2” at its widest point, the rounded ends have a diameter of 3/4” and the curve at the base is 10” diameter. So if I put my 3/4” bit on the router and give it a 5” radius arc that should do it.


    Using a Jasper jig with the 3/4” bit requires measurement since its scale is calibrated for a 1/4” bit. Then with the bit lowered I swung it to either extreme and placed some temporary blocks to prevent the cut from going past 1 1/4” from the center line.


    After that it was just a matter of running a straight line from the highest point of the circle toward the 1 1/2” “nut”, following the line.


    I’m sure there is an easier way to do it but that’s all I could come up with given the absence of information from my books. I’ll wait for someone to tell me how it’s really done.
    BritFunk likes this.
  8. Wow, math.:cool: I usually just trace the neck heel on the MDF and cut it out and use files and a spindle sander to refine it. I don't remember who I saw posted it first but I have had a template that ended up oversized and waxed the heck out of the end of the neck and used epoxy to fill in the template and make a tight fit.
    RobertUI likes this.
  9. I intend to try this first chance I get:
    mnats likes this.
  10. mnats

    mnats Supporting Member

    Feb 2, 2013
    Hmm...looks like double stick tape under the neck and blu tack were the two missing ingredients from my attempt. Thanks for the vid. Pretty sure someone here posted something similar but I haven't been able to find it.

    Wonder how much the thickness of that tape around the bottom of the neck plus the shrinkage from the resin will affect the final result? I like the way the Warmoth parts fit together so there's virtually no play and the neck just aligns with the bridge. That's what I'm aiming for with my pocket which is why I tried to get those sides as perfectly aligned as I could.
  11. mnats

    mnats Supporting Member

    Feb 2, 2013
    Some time ago I bought a truss rod from LMII that I thought I’d be able to use for this build. But since it’s going to be a medium scale it won’t work. I’d mis-calculated the length I needed when I found something on Ebay that was about what I’d thought would work. It arrived with an interesting description.
    Something to do with the blue plastic wrapping around the length of it, I guess.

    In any case I quickly worked out, once it had arrived, that 580mm was too long to work for a medium scale. Fortunately, unlike the one from LMII, it was threaded only on one side rather than having a left and right hand thread on opposite ends. So I took one of those blow torches you see sushi chefs searing a piece of fish with and some bronze brazing rod, removed the blue plastic, cleaned the grease off with some thinner then heated it for an incredibly long time until the metal flowed between the square and round pieces of steel. Then I hacked off about an inch so it would fit.
    There are some things to like about the Chinese truss rod - their welding was very neat and the business end has the threads enclosed in a sleeve rather than exposed. The round rod does not rotate but only serves to pull on the opposite end. However, there is no plastic sleeve on the round rod so it may buzz unless I do something to damp it. It seems to bend in either direction without any patented mechanism too.
    IMG_0527. IMG_0528.
    So I hadn’t mentioned before that the piezo system I’m using is a Dtar timber-line. I know it’s made for guitars, but I figure that the preamp probably isn’t configured to roll off below 80Hz. I read some of Turner’s comments about piezos that made a lot of sense and he mentioned something that I’ve always thought but put differently to the way he does. The difference between an active and passive electric bass is only where the preamp is located. In the case of piezos it makes more sense to put the preamp closest to the pickup due to the high impedances involved. I think he said something like they don’t make good line drivers.

    Anyway, I knocked out a jig for the router on the table saw and using a nail gun - great time saver.
    Thought I would use the endpin jack after figuring out that I hate side “input” jacks - who knows, I might hate this as well. But it looks pretty clean, I think.

    Attached Files:

  12. I think you should name your next band “Blue Pole.”
    RobertUI likes this.
  13. mnats

    mnats Supporting Member

    Feb 2, 2013
    Wasn't there some other Blue Guy band or somethin'?

    At 36mm the frame of the body was getting a little thick for my taste so I knocked out a stripped down version of the router planing jig shown in this thread.
    After taking it down a couple of passes I was surprised to see it looking so uneven. But when I measured around the edges the variation was around +/-0.015" so close enough for this job I think since a thin layer will get glued on top. I think I was right on the internal glue line at this depth.
    Then I took a Jazz Bass body, a pair of calipers and traced out the forearm contour. After trying a number of ways to secure it while I worked I found that the most comfortable way was to hold the body with the contour end away from me and a Shinto rasp in the other hand. There was something satisfyingly tactile about doing it this way that I had not experienced with other forms of woodworking. Funny, the plies don't look as objectionable as I thought they would when exposed this way.

    Attached Files:

    b3e and T_Bone_TL like this.
  14. mnats

    mnats Supporting Member

    Feb 2, 2013
    Enough of the zen woodworking, time to get out the big guns. Finished off the forearm contour with the belt sander.
    Thinking ahead to the neck and remembering about once failing at fretless I decided to make a lined fingerboard. Since I also want a fretted medium scale I bought one of the Stew-Mac saws that fits the new table saw. So a detour while I make a sliding crosscut table or what Erlewine refers to as a "shooting board". To make sure the thicker part of the saw clears the top I used a normal blade to cut halfway through the sliding table. Then make sure the saw is sitting square then raise the blade to cut the first partial slot. This gives a reference from which to attach a newly cut straight edge of a board. Then a hardwood fence on the opposite side screwed to the table.
    I also want a table mounted router to cut that truss rod slot and for other functions so started looking around for one that the height could be finely adjusted and that did not have a switch that required user contact to stay operational. I read an article about how Makita takes old designs and tooling, moves production to China to save costs then builds these older designs at low cost.
    The Makita MT M3600 has a simple toggle switch and a large knob to control the height of the bit. It also has a 1/2" collet with a 1/4" adapter included so I can still use some of my older bits with the new router. So heavy compared to my 1/4" 3620 so I'm glad it will be mounted to a table most of the time.

    Meanwhile I built another MDF jig to route the battery compartment for the 18 volt power supply for the piezo preamp.
    Still trying to work out how I'm going to bend that 4mm thick Baltic birch ply over my forearm contour...

    Attached Files:

  15. mnats

    mnats Supporting Member

    Feb 2, 2013
    I originally posted here as a way to keep motivated to see this build through, but also because I'm inexperienced with making instruments. There wasn't much that turned up in a search about bending plywood over the forearm contour here so I had a look around and got lots of opinions. The one that sounded good to me was to take thin sheets of material and glue them in layers to make your own ply. That way the glue would serve to maintain the curvature.
    Using the router jig with 4mm Baltic birch only ended up producing a lot of wasted material. I had not accounted for the fact that a thin piece made thinner would start to curve and flex so I ended up tearing gouges in a good sheet of ply.

    So I thought I would try to cut thin kerfs in the top using the new fret saw and crosscut table. I figured out where the top would have to bend the most then drew some boundaries around that area. Then I took the scrap piece that I'd cut the top from and worked out the line that was 90 degrees.

    Used some scrap to keep the scrap aligned on the table saw crosscut jig.

    Then used some carpet tape to stick the jig to the top:

    To make a number of evenly spaced kerfs I cut a piece of resawn decking and cut a single line partway through. I found that an X-ACTO blade fit the kerf fairly well - better than anything else I had on hand.

    The easy way to take material away from an X-ACTO is to break it. Use eyewear as the flying piece can be unpredictable.

    Ordinarily I would use some slow setting epoxy but since I didn't want to wait I used some Zap-A-Gap.

    With the kerf jig screwed down I made a test piece.

    Then tried it in the material I'd be cutting to get the depth correct.

    With jig 1 and jig 2 in place I tried the first cut, then quickly worked out that I'd built the jig backwards since the piece would be moving incrementally to the right where there was no material to index the broken off Exacto blade.

    There was just enough blade though to make seven cuts that I hoped would be sufficient.

    Looks like it might work.

    Can't remember where I got this from but it's one reason why I disagree with Melvin Hiscock and his opinion that fingers make the best spreader for glue.

    Various eras of Quick-Grip clamps.

    For a long time I've had this piece of bocote that I bought long ago on a trip to Southern Lumber (now gone). I want to make the bridge out of it with the 7 degree tilt or whatever it says in the manual that came with the pickup. But then again this is my junk 1st build so maybe I'll save it for a better instrument. There's a YouTube video of someone making a router jig using a wedge shaped shim under the piece you're using as the bridge. Any other advice is welcome...

    Attached Files:

    Last edited: Mar 30, 2018
    Tom McClintock and mapleglo like this.
  16. mnats

    mnats Supporting Member

    Feb 2, 2013
    I'm happy with the way the contour turned out:
    Although when I was using the flush trim bit it fell into the hole I'd drilled for the end pin jack. Oh well, that's why this one was made mostly out of a piece of plywood that was going to get thrown out. Glad I did not do this with my good blank.
    floydman, BrBss, JIO and 10 others like this.
  17. ctmullins

    ctmullins fueled by beer and coconut Gold Supporting Member

    Apr 18, 2008
    MS Gulf Coast
    I'm highly opinionated and extremely self-assured
    Nice job on the contour!
    BrBss, Dadagoboi and mnats like this.
  18. mnats

    mnats Supporting Member

    Feb 2, 2013
    I’m anxious to work out how the piezo element is going to route through the body to the bridge so thought I’d work on getting the bridge ready today. After sawing it to thickness I remembered how sweet bocote looks before it turns dark with age.


    I'll start with a plain rectangular blank then get the saddle slot cut to the 7 degree back angle specified in the installation instructions. I wasn't able to find a tool locally that would cut the rounded bottom specified though so it will stay flat for now. Found that video I mentioned previously. The presentation is interesting but I found the content useful.

    Took my medium scale PJ build and measured the angle of the saddles in relation to the strings and found it was about 6 degrees. I don’t know how that will translate to nylon coated flatwounds that I’ll use on this fretless but with my intonation it won’t make much difference at first.


    As shown in the video linked to above I made a ramp out of Baltic birch scrap. Then I basically copied the same design shown there except I made a guide for the router at the 6 degree angle that I measured from the existing bass.




    Toward the end I got impatient and quickly nail gunned some stops down so I did not have to worry about making the slot too long.


    Made a quick first pass, then took it to full depth gradually.


    Anyone see what the problem is with this jig and the result?

    Matt Liebenau likes this.
  19. mnats

    mnats Supporting Member

    Feb 2, 2013
    Needed to fit a neck to check the bridge placement and a few other things, so I cut through the recent top using the measured out jig shown earlier. Had to cut several different thicknesses of the jig to deal with the short length of the pattern cutting router bit. I found if I indexed the hole at the 34" bridge mark centerline where the nail is then it was easy enough to match the top of the jig area where the neck is exposed on the left in the photo below.


    Neck is a 34" scale MIM Fender. Fit is not as tight as the Warmoths I built recently but not bad at all. I was worried because the Jaguar document I downloaded from a thread here showed pocket measurements slightly larger than the measurement of the neck itself, presumably to compensate for neck finish.


    It's exciting to hold something that feels almost like a bass, though with the not finished body with no hardware and those bulky Fender tuners it has some serious neck dive at the moment...
    Matt Liebenau likes this.
  20. mnats

    mnats Supporting Member

    Feb 2, 2013

    Mistakes like the router slip at the end pin jack hole really gnaw at me. I end up thinking about these kinds of things all night. Then in the morning I sometimes have an idea about how to fix them.

    I found a screw head that was about the right diameter as the gouge.


    Then I screwed it into a piece of scrap Baltic birch ply that I had glued to double thickness the day before.


    Actually, I unscrewed it a little so there was some distance between the screw head and the material. Then I put the flush cutting bit in the router and made a half cylinder.


    The sandpaper I used to make it flush was probably a little rough so it ended up taking a small nick out of the top material. But I'm satisfied enough with the patch to be able to get a good night's sleep now.


    As for those holes the bass was always going to be string-through. I thought this might give me some more freedom as to which strings I could try since medium scale strings tend to be a little thin on the ground. But I had not thought through the electronics that sit in the end pin jack so the strings will have to clear that area. They are a little further back than I had envisioned. But I tried out a long scale string and it should be sufficiently long to work once I've made the new 32" scale neck.

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