Router Planing Fixtures

[MovinTarget]

That wasn't too bad and should do the trick:

L-joined 1x2s so i can flip them for something starting less than 1.75" or something a bit taller... i am not going to bolt these on to keep the flexibility. Railes are 36" long so unless I am planing a full scale+ thu-neck piece, I should be fine...

 

[MovinTarget]

When planing boards with some bowing, is there an established starting point? I.e. if there is a hump towards the middle, should I plane hump-side up first or hump-side down? The former kinda makes sense since you'd at least have the ends making contact so it doesn't rock, but I wasn't sure if there is more of a science to it...

 

[Bruce Johnson]

When planing boards with some bowing, is there an established starting point? I.e. if there is a hump towards the middle, should I plane hump-side up first or hump-side down? The former kinda makes sense since you'd at least have the ends making contact so it doesn't rock, but I wasn't sure if there is more of a science to it...

Yes, the usual procedure is to surface the hump side (the convex side) first. Mount it in the bed and put some little shims under the center arched gaps, to make sure it doesn't spring down under the router cutting load. Rout that side flat, removing the hump. Then flip it over and rout the back side, bringing the high edges down to meet the middle, and to your desired thickness.

 

[MovinTarget]

Thats what I thought but wanted to make sure. Thanks!

 

[dwizum]

When I am flattening boards like that, I like to scribble over the whole face of the board with chalk to give myself a positive confirmation that the router has actually touched the whole surface (removed the chalk) and therefore the board is flat.

 

[MovinTarget]

When I am flattening boards like that, I like to scribble over the whole face of the board with chalk to give myself a positive confirmation that the router has actually touched the whole surface (removed the chalk) and therefore the board is flat.

That's what I did when I leveled the joining edges over the weekend. I had to really rub the chalk in b/c the sides had this ribbed feel, like they were not cut with a good blade, on top of a bit of bowing...

I doubled-sided taped 60 grit to a 4' level and mounted it to a tall board as a guide and ran the wood back and forth until flat:

Works pretty well but takes a bit of elbow grease and I swear 80% the effort goes into the last 10% of the leveling since you are sanding the majority of the edge down to get to that lowest point.

Too about 8 hours off and on to finish 8 boards (both edges).

 

[dwizum]

Next time, just clamp your router planing jig to a table such that it hangs off the end, or rest it across two sawhorses, and put the boards to be jointed in the jig with edges facing up, and use your router to joint them in about 30 seconds!

 

[MovinTarget]

Next time, just clamp your router planing jig to a table such that it hangs off the end, or rest it across two sawhorses, and put the boards to be jointed in the jig with edges facing up, and use your router to joint them in about 30 seconds!

Yeah, but you gotta be REAL sure you have things straight of you'll pull off a lot more wood that you might want. I am not saying I wouldn't use that technique, but I can't afford to take too much off these boards for this project...

I know my way was slow, but it is very controlled and it maintains a flat level surface effect across the entire board allowing one to be able to only take off as much as is needed without have to worry too much.

 

[dwizum]

I've done all my jointing this way for a few years now. At first it was a bit awkward until I got the process down. I have a pair of gauge blocks that are basically 3/4" plywood bars with a smaller piece of 3/4 ply glued to the bottom in the middle - I set them across the top rails of the jig near either end and then gently clamp the workpiece in the jig, and nudge the workpiece upwards until it's top edge just barely touches the bottom piece of ply on each gauge block. Then I tighten the clamps. This sets the workpiece at a consistent distance below the rails. Then I lower the router bit until it just barely contacts the workpiece and take a first pass, then lower 1/64th at a time until the edge is true. Nice perfect edges, no snipe, and you can take off as little or as much as you want. For thin boards I just clamp mdf strips into the jig on either side to stabilize.

 

[MovinTarget]

Router Planer worked well! I actually took the rail guides off the router sled as they were too tight and just ran it free-hand and it worked well. Glad I used my fixed-router base as that gave me fine depth control of the bit height.

 

[Bruce Johnson]

Another modification/variation to a specialty router planing fixture:

Back on Page 4, Post #74, I showed you a small specialty fixture that I made up for routing the fingerboards off of Jon Wilson's GuitarViols. I used it on one of his acoustic models.

Yesterday, he brought me the neck from one of his electric models for the same operation: rout off the fingerboard. His electric model neck has a more conventional flat tilted headstock, and it bolts on the body with two 1/4" machine screws in line on the centerline.

So I made up a new mounting fixture to locate the neck in the previous twin rail fixture. I point it out because it's a simple way to mount any bolt-on neck in this type of fixture, which squeezes the two sides together with clamps.

The neck holding fixture is a flat board (a scrap of 3/4" MDF with oak veneer facing). At the headstock end, I cut a notch to clear the tuners, and a small bevel that the headstock rests on. At the heel end, the heel is bolted down using two 1/4-20 bolts on aluminum spacers. That holds the neck securely enough that it doesn't move around on the board.

Look underneath the board at the triangular things. Those are two "feet" that are screwed to the neck board. They are the right height to hold the neck so the fingerboard glue line is approximately parallel to the rails, and the highest end of the fingerboard clears the router base. I cut the feet triangular and slightly rounded the bottoms so that the whole thing can be gently tipped side to side, to adjust the neck level in the fixture.

You can see how I'm using my aluminum depth-stop gauge bar to align the neck, to get the glue line parallel to the rails, lengthwise and crosswise. I added a small shim under the forward foot to align it lengthwise, then tipped it slightly to align it crosswise. Tighten the sideways clamps and reach for the router.

This is one of Jon's cast epoxy fingerboards. It has a carbon fiber bar down the center, but it has big hollow areas underneath. Solid epoxy would be real heavy and expensive. It's only glued to the wood along the perimeter. So, I didn't need (or want to!) rout off the entire fingerboard. I just routed about 1/4" wide along each edge, slowly going deeper until I just touched the wood. Then the center section of the fingerboard lifted right off.

I forgot to snap pictures of the finished operation, but you get the idea. After I made up the holding fixture, the actual operation took maybe 10 minutes. Followed by 10 minutes of cleaning up all the epoxy chips!

This is another example of how to use a router planing fixture to do a precision machining operation on an instrument neck. The final glue line surface on the neck is flat and true to maybe +/- 0.002". Within a half hour, Keith and Jon had a new fingerboard glued on.

 

[dwizum]

That was very timely, Bruce. The next thing I need to do on the bass I've been working on with my son is clamp it in a router planing fixture to flatten the neck before gluing on the new fretboard. This gives me some ideas!

 

[MovinTarget]

That was very timely, Bruce. The next thing I need to do on the bass I've been working on with my son is clamp it in a router planing fixture to flatten the neck before gluing on the new fretboard. This gives me some ideas!

Along this thought, I've just finished the "rough" planing of a couple of neck blanks using this router planing jig, but now I need to do the real smoothing of the face that will glue to the freboard. I am tempted to just get a 4' long 3/4" MDF board and get 80 grit sandpaper in roll form (thank you Amazon!) and anchor it at both ends and just run the board evenly back and forth so that it stays flat and all points get the same level of attention to bring it truly flat.

I don't mind the work, but is this a wise way to go about it?

Or is the better question, "Why isn't my work join-ready after using my jig?" I never expected it to be...

 

[Bruce Johnson]

"Why isn't my work join-ready after using my jig?"

That would be my question too. To me, the router-planing fixture, done right, is the best way I know of to prepare a join-ready surface. All of my surfaces to be glued up on my instruments are cut with routers and fixtures. Laminations, fingerboard surfaces, body tops and backs, etc. It's the best method I know, in both accuracy and speed.

Even using a metal-working-type milling machine isn't any more accurate, and it's much slower. A flat block with sandpaper is a whole lot more work, and you have to try real hard to get the accuracy equal to what you get with the router-planing fixture. Accurate sanding, whether by hand blocks or by machine, requires very consistent pressure, and that's hard to do.

If you aren't getting really good true join-ready surfaces from your router-planing jig, then something's wrong. Let's look at that.

 

[MovinTarget]

Okay, that's what I needed to hear... even if its not what I *wanted* to hear...

Perhaps my problem is in my wood itself, I'm working with 4/4 maple that's been roasted it's shrunk even more and I'm not so much thickness planing as just trying to flatten it out w/o taking any more than I have to. I would probably have better luck with thicker pieces so I can completely resurface it and still have the thickness I need...

For the record, here is my router bit:

It is a 1" Dado/Planer bit w/ 1/2" shank... Notice how the cutting blades angle "up" towards the edges? I sometimes get circles on my wood if it's too shallow.

 

[Bruce Johnson]

That's the right router bit to use. I use the Freud version for my big router planing, the body tops and backs. For the necks and neck lams, I usually use a short (1" tall) 3/4" dia plain router bit. If you are getting an uneven surface, it means that your fixture rails aren't straight and/or the board is flexing or moving in the fixture under the cutting load.

 

[MovinTarget]

That's the right router bit to use. I use the Freud version for my big router planing, the body tops and backs. For the necks and neck lams, I usually use a short (1" tall) 3/4" dia plain router bit. If you are getting an uneven surface, it means that your fixture rails aren't straight and/or the board is flexing or moving in the fixture under the cutting load.

It *might* be moving as I usually don't clamp everything down six ways to Sunday... I'll try that next time... I have some horribly warped boards I can practice on...

 

[dwizum]

Don't worry so much about clamping as shimming. If the board is warped, I use a combination of Popsicle sticks and cardstock shims to get support under the sections that don't touch the workbench before I clamp it in the jig. The clamping will really just hold it still, it won't stop it from flexing.

The only times I've had pieces come out of a router planing jig that were not ready for use was my experiments a few pages ago with thicknessing very thin stock for acoustic back and sides. Other than that I treat it the same way as Bruce, the whole point of the router planing jig is to get something ready to join.

 

[Bruce Johnson]

It *might* be moving as I usually don't clamp everything down six ways to Sunday... I'll try that next time... I have some horribly warped boards I can practice on...

Look at how almost all of my fixtures clamp the board side-to side. That's important. If you clamp it or screw it down vertically, you'll probably distort it in the vertical plane. Then you rout it, unclamp it, and it springs back to warped or distorted shape. The whole point of these fixtures is to hold the board still, in its distorted shape. Then use the router to cut it flat.

 

[MovinTarget]

No, I totally do what you both are suggesting in the sense of doing things from the side. I use pieces of a cheap yardstick so its fairly straight on the sides to keep pressure even, I just wasn't using a clamp to tighten them so much it was mostly just by weight and friction.