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I made a router jig for opening truss rod channels. It is simple to build, easy to use and it works very well, much better than the usual simple fence or even the double fence types. This is how it looks:



The router base has two identical pieces, each one with a fixed axis and a screw that lets you modify its angle to adjust the space between the inner walls, that can go from around 47 to 80 mm. The best thing is that when the inner walls are parallel then the bit is at the center of the channel, no matter the space between the walls. With a quality router (Makita) and the jig installed using the four base screws, this is precise to around 0.3mm, which is enough for me. I have measured some cheaper routers and the bit was not in the center of the four base screws, but this can be corrected by gluing a wood shim to one of the inner walls.

It takes me two minutes to adjust to any neck blank width. Another advantage is the two fences, that make it easier to use than one-sided router guides. I hope that someone finds it useful!

Great idea!

Pat

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formerly known around here as burbank
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http://www.patfosterguitars.com

Fantastic bit of tooling.
Me likey!

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"Act your age, not your shoe size" - Prince

Fernando, I think this is a nice jig concept--one of those things I wish I had thought of. Are you mounting your router in a table?
Patrick

I would love to try this. I've routed TR slots with a table router, and it's hard to see what's going on, and with my cheap setup, it's hard to get it centered exactly. This would do the trick. Thanks for the idea!

I'm glad that you find it useful!

cphanna: I have a table with several routers for different operations, but I've always used a handheld for this. I like to make the channel in three steps, and with a plunge router upside down that is a complication, because you are working against the weight of the router and also the springs in it. A router that is not the plunge type may be common in USA, but here in Spain (and even Europe) it was extremely hard to find some time ago (I've just checked it again and I can see that now there are some shops selling "conventional" routers in Spain!)

Nice design! great idea.

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Steve Sollod (pronounced sorta like "Solid")
www.swiftcreekguitars.com

Beautifully simple! I love your idea.
This should go in the fixtures, video and picture tutorials section as well.
Mine's a lot clumsier and takes up a lot of storage space (a guide bush in the router and a matching slot between 2 bits of 18mm ply fixed to the neck blank)

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Brilliantly simple!

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Great idea. Thanks! Its difficult to get the route exactly in the middle and some of my neck blanks are just barely big enough.
What should we call it? The Jaen Jig?

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Pat

I'm not seeing the picture and for some reason I'm having a hard time picturing what you're talking about. Is there a picture of this jig?

Best,


Jonas

Fernando, thanks for sharing this with us. This jig is elegantly brilliant.

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Alain Moisan
Former full time builder of Acoustics, Classicals and Flamencos.
(Now building just for fun!)

I'm trying to setup for necks using as few fixtures as possible. This fits the bill perfectly! Build them into a polycarbonate base and you'll be able to see everything perfectly.

How does one cut the curved slots in the guides?

Edit: You can probably just drill them and connect the dots with a fret saw. Duh.

I'd be using my router/circle cutting jig (normally used to cut rosettes, sound holes etc.). Not a Dremel one!

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Yep, just use the hole location for the fixed point on each pawl before you drill out for the bolt.

I'm totally going to use this.

Centering.

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Pat

I like this!

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Another day, another dollar.

Filippo:

Most of my necks are made of three "side" laminations, and then centering becomes important. If you keep the thickness of the laminations always the same, then you won't need this flexible centering jig either. I tried all the time, but the truth is I was constantly moving the fences in my router. For example, sometimes I needed to use a thicker or thinner center lamination, or some more complex patterns:




This is complicated by the problem of thicknessing the wood blanks, which I always do before I cut the laminations from them. Those laminations can go to several different necks.

Centring is certainly one thing, but there's more (for me).

My router table is already symmetrically laid out with bolt holes, so I would be using this idea on my router table. Also, due to the nature of some of the jobs on necks that I do on the router table, I need a fence both sides at the same time (not worth going into the whys and wherefores now), so a self centring double fence that automatically centres and re-centres on the same or different width pieces is a great idea for me. An alternative is a carriage that runs in the mitre-slot of the router table with a device that self centres to the cutter, working on similar principles to Fernando's idea. That would work better for me, though would be more work to build and much larger to store. It would be a lift on, lift off fixture, rather than having to screw four bolts into the router table. Given that I'd only be saving about 30 secs per setup, I'll likely go with the cams on the router table version.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Filippo:

Your centering jig is more complex, and it needs to be so because it works on a tapered neck. My jig only works for neck blanks that have their sides parallel -- I think this is where the confusion comes.

The center-line finder came to my mind, too. I think this works similarly. Loosen both sides together and squeeze them against the work piece? Fernando?

I can either make this for $30, or get an edge guide for $40 (either this or this). Still weighing.

I like it!

Filippo, it appears to me that you would place the neck between the "wings", squeeze them against the sides of the neck, then tighten the bolts........and the router bit will automatically be centered to route the truss rod slot. Also would have a fence on both sides of the neck while routing the slot.

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Formerly known as Adaboy.......

seems really dangerous to squeeze the wood in that gap while a spinning bit is doing its thing...what if it binds up, where does all that energy go(if the motor doesn't quit)?

I've just made a drawing that explains it:



This is what you'd see when adjusting the fences for a narrow (left) and a wide (right) blank. Notice that the router is more skewed for the narrow blank.

Now that is funny. Some folks make adjustments before starting the equipment with the dangerous blades.....<smile>

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Formerly known as Adaboy.......