How much body routing (by hand) to do before putting on the top?

Discussion in 'Luthier's Corner' started by rwkeating, Apr 8, 2018.


  1. rwkeating

    rwkeating

    Oct 1, 2014
    Chicago
    none
    My next build will have a top (about 3/8" thick) on the body core. I'd like to take advantage of this and route the body (for the PUs,) put the top on and route the top. I am working by hand with a router plane. Even with very careful measuring I don't think I will be able to exactly route the top in the same place where I've routed the body. Should I just oversize the pickup routes in the body, put the tops on and then make the exact correct size on the top plates? Being 3/8" thick I thought this might be the way to go, but I am not sure.
     
  2. HaMMerHeD

    HaMMerHeD

    May 20, 2005
    I'm curious why you want to route the cavities before you glue the top on.
     
    mrcbass likes this.
  3. rwkeating

    rwkeating

    Oct 1, 2014
    Chicago
    none
    TLDR: looking for some shortcuts :)

    It started with the idea of being able to cut out a section of the body for the control cavity (rather than routing) and then putting the top on. Then I thought it would be good to put the wire channels in (before gluing on the top) to avoid the dreaded "drill in on an angle and don't get the angle wrong" work. So that led to thinking of doing the pickup routing before putting on the top too. Each one of those would cut down on the time and hand work by routing out more via Forstner bits than I normally would.
     
    reverendrally likes this.
  4. Englishman

    Englishman

    Apr 26, 2017
    Detroit
    Chambers and wire channels (or in my case, chambers AS wire channels) for sure. Pickup cavities I don't get though, it's not much of a short cut if you have to do it twice.
     
  5. Beej

    Beej

    Feb 10, 2007
    Vancouver Island
    In order to get things to line up really well, I think I would probably glue the pieces together in a full size blank. That way, your indexing of the pieces will always be perfect, as the edges can just be glued to line up. Then if you have a template for the body shape, it should allow you to rout the top holes in alignment with he holes you have already cut in the core.
     
    rwkeating and reverendrally like this.
  6. 1. If you can, I'd thin that top down to 1/4" or even 5mm.
    2. Think of every possible thing you want to do with the instrument... ever. Ie, extra PUs and or electronics and plan for that NOW.
    3. Chambers can be bigger than you imagine. Then probably bigger still.
    4. It's possible to shield the cavity (with paint) before gluing the top on, including the inside of the top.
    5. Make a routing template.
    6. Be more anal about the finish of the inside of the chambers than the rest of the instrument. :D
    7. When you've finished routing it all out (before gluing on the top), take a pic of it so you remember where you put your wiring channels. Don't ask me how I know this. :(
     
    mikewalker, RobTheRiot and rwkeating like this.
  7. Bruce Johnson

    Bruce Johnson Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    I make my Scroll Bass bodies "half and half", that is, the top and back are equal thickness; 0.700" thick walnut. I rout a whole bunch of chambers into both the top and back before they go together.

    IMG_5666B.jpg

    IMG_5682B.jpg

    The trick to keeping everything lined up is dowel pins and holes. If you look close, you'll see four small 1/8" holes in the walnut, right down the centerline. These "reference holes" holes are drilled in the walnut blank using the Master Pattern, which has drill guide bushings in it. These holes are drilled all the way through the top, but only 3/8" deep in the back, from the inside. Although there are four holes (for some complicated reasons), I really only use the two outermost ones for the operations on the AMB-2 model bodies.

    All of my routing templates also have those same reference holes, all drilled using the same Master Pattern. The holes go all the way through the templates, so all the templates flip over and can be used from either side. This makes sure that the routing operations in the top and back are identical and exactly lined up. Plus, it's simple to make a left-hander when needed.

    The templates are all made from 3/4" MDF. I have 1/8" x 1" long steel dowel pins in the reference holes in each template. I can quickly tap them flush on one side, then they are sticking out 1/4" on the other, so they can plug into the walnut. I slightly taper the two ends of the dowel pins on the grinder, to make it easier to find the holes in the walnut. Also note the round holes in the template, right near the pins. Those are so I can see down in there to get the pins lined up with the holes in the walnut.

    The pins alone hold the template tightly aligned on the walnut blank during the routing. I don't use any tape or anything. In some operations, I clamp the sandwich down to the bench top, just so it's not sliding around. In other operations, the sandwich is just resting on a rubber non-skid mat on the bench top. It only takes a few seconds to pop the template off of one walnut blank, and onto the next one. And it's only a few more seconds to flip the template over and tap the dowel pins the other way, to switch from a top to a back.

    Skipping a few steps, here's three sets of walnut tops and backs with most of the routing operations done, and the perimeters bandsawn out.

    IMG_5694B.jpg

    I paint the inside of the F-hole cavities before gluing the top and back together. Much easier than trying to spray them later, from the outside, through the F-holes! I use masking plates, cut from 1/8" masonite, which plug into.....wait for it......the same two reference holes. I made up those L-handle pins to quickly plug and unplug them. The pins are just a short length of 1/8" steel rod, ground tapered on the ends and bent.

    The masking plates are easy to make. They are routed right from the routing template that cuts the actual recesses, plugged into those same ol' reference holes.

    IMG_5695B.jpg

    Here are the tops and backs, ready to glue together. To align them during the glue-up, I use short lengths of 1/8" white styrene rod stock, the same as I use for my side dots. These plastic dowels are short enough that the reference holes are still open on the outside of the top. After the glue-up, another set of templates plug into the reference holes on the top, to cut the external chambers.

    IMG_5707B.jpg

    It's all about carefully planning out your tooling. A small time investment in (shudder) engineering and templates pays off in big time savings as you start making batches. The key to everything is those darn reference holes. They make everything line up. I have similar holes and pins in my neck process.

    In case you are wondering, those two aluminum bars are the Bridge Bars. They fit into those slots in the top and back, surrounded by epoxy. They have threaded holes that the tailpiece bolts down to, and there are sockets in the forward end that the bridge jacking screws rest in. The little extra threaded hole on the one bar is for the bridge grounding wire. Another of those legendary, mysterious, hidden Brucification tricks!
     
    Last edited: Apr 9, 2018
  8. Can't tell you how much I LOVE templates. :)
     
  9. HaMMerHeD

    HaMMerHeD

    May 20, 2005
    Ok, now I'm curious why you're using a hand router plane.
     
  10. I do this on all my instruments. While Bruce's method is far more accurate, so far I haven't made the same instrument shape twice so I haven't invested in that kind of templating (however impressive!). I normally figure out where I want chambers and I route the bottom with those, then I place a piece of paper over the bottom, and trace out the chambers, cut the holes out and transfer that to to the top to line up the chambers, it works great. A side benefit of this is you can route the control cavity out then cut the cover out, so it matches up perfectly.

    On the pickup routes: I will do a pool route on the bottom that is bigger than the pickup, then I route the top to make the pickup fit very close. It's barely better, but it guarantees there is no binding as you slip the pickup in, I like a tight fit there.
     
    rwkeating likes this.
  11. mapleglo

    mapleglo Gold Supporting Member

    Sep 7, 2013
    phoenix, az
    rwkeating likes this.
  12. HaMMerHeD

    HaMMerHeD

    May 20, 2005
    Fair enough. I really dont know the answer, because my processes generally start with power tools for efficiency. I do have a number of hand planes, gouges, and such, but they are mostly used for fine adjustments.

    Good luck!
     
  13. rwkeating

    rwkeating

    Oct 1, 2014
    Chicago
    none
  14. tr4252

    tr4252

    May 27, 2013
    Just a comment first; I looked at your tapping instrument thread, and was pretty impressed. If you're doing that well with hand tools, you would probably do really well with a router.

    I have to confess, I don't fully understand the technique you were describing in your first post. Are you drilling out a bunch of holes to make a cavity then cutting out the scrap web with chisels and/or saws perhaps? If that's the case, I can fully appreciate your wanting to build a body one layer at a time.

    As has been suggested above, guide pins are important, to maintain alignment. How many times will you flip it over, take it apart, etc. before you slip or lose track of the orientation? Happens to me, anyway. Regarding pins, you don't have to drill them all the way through your wood layers. You could drill, say 1/4" short of the surface that would be visible when the body is completed, on one piece, then transfer the hole locations to the other piece with "transfer pins. This is very accurate; I will elaborate if you wish.

    I remember that I used a lot of hand tools on guitars and gunstocks years ago, simply because I lived in an apartment and knew the neighbors wouldn't tolerate the noise.

    Otherwise, I'd have to suggest a small router. I know it's not what you asked, but I think the labor saving would permit you to do more/faster of the interesting work you are doing.

    I apologize for any misunderstanding or redundancy on my part.

    Tom
     
    rwkeating likes this.
  15. rwkeating

    rwkeating

    Oct 1, 2014
    Chicago
    none
    @tr4252 on my 3rd build (a bass) Build #3 (This time it is actually a bass! 5 string fretless, still mostly hand tools.) I glued the top on and then proceeded as if the body were just one piece. That meant having to be very careful as I routed out the pickup cavity to full depth. I thought if I could rout out first and then put the top on, I would only have to be careful with the top routing (only 3/8" thick) and the route underneath could just be a clean rectangle slightly oversized.
     
  16. T_Bone_TL

    T_Bone_TL

    Jan 10, 2013
    SW VT
    Which is exactly what @Jisch suggests in post 10. It's a valid approach with either tool-set.
     
    rwkeating likes this.
  17. tr4252

    tr4252

    May 27, 2013
    Thanks, now that I visualize it as you described, an oversize rectangle would be a good solution IMO.

    Tom
     
    rwkeating likes this.
  18. You can also cut the pickup routes before you glue the top on, that way you can use a file to make the corners, it's a lot easier than trying to file it after it's glued in.
     
  19. rwkeating

    rwkeating

    Oct 1, 2014
    Chicago
    none
    Such an obvious solution. Why didn't I think of that? I thought I had come up with all possible options, but nooooo .... thanks!
     
    Jisch and T_Bone_TL like this.
  20. Bruce Johnson

    Bruce Johnson Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    Heh. We were just talking about Router Planes. One of the other woodworking guys here in the Lab was cleaning out his shop, and I saw this on the table. I asked him if he wanted to sell it, and he gave it to me!

    This is a Millers Falls Router Plane, probably from the 1950's. This was the tool you used to do "routing" before those new-fangled things with the electric motors were around. With some muscle and patience, it will cut grooves and slots and cavities. Silently! (Except for your personal grunting).

    I'm going to have to sharpen it up and mess around with it. I'm not sure exactly what I'm going to use it for yet, but I'll find something.

    IMG_5721B.jpg

    IMG_5722B.jpg

    IMG_5723B.jpg

    IMG_5724B.jpg

    The blades are L-shaped; I got two extras. The round wheel is the fine adjustment for the cutting depth.
     
    b3e, nouroog, reverendrally and 2 others like this.
  21. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
    Aug 1, 2021

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.