Official Luthiers Forum!

After 10 years, I've finally decided to give up my shop-made hand held binding jig.
I thought about a Williams style jig but just don't have room and the de Jonge style jig like CLS sells looks nice and compact, easy to make, etc...but it seems like getting the various size guides precision machined would be pricey.

So I've pretty much settled on a tower style jig. I do have one question, though:
Do any of you guys with experience with these think it would be worthwhile to build a small amount of rotation (swing) into the carriage? My understanding is that one of the shortcomings of this type of jig that moves only in the one axis is that, on tight curves (like the waist) where there is a steeper apparent arch, you end up with a slightly U-shaped channel rather than a square channel.

In practice I can't imagine it's much of an issue but since I'm building this thing from scratch I figured that I'd try to produce something that will produce as close to a perfect channel as possible.
Building a small amount of swing into the carriage would only cost me about $15 more in parts and a negligible amount of extra time. What do you think?

I was also kind of thinking about making a doughnut with 2 points of contact on either side of the cutter rather than the flat-faced round doughnut that you see on pretty much every machine. I think it would create a more accurate cut but my apprehension there is that the decreased surface area of contact might slightly dent/damage the top and might not slide quite as well (maybe 2 side-by-side bearings for the points of contact?). I'll probably make both types and test it out.

That's generally not an issue in the waist area because the lengthwise plane of the back is almost horizontal at that point. However, if you use high dome backs (< 10' radius) it can potentially be a problem in the cutaway area (if you do cutaways), parallel to the fretboard. In practice, most times it isn't. You can get round it by tilting the head end of the guitar up a little.

For a "tilt-head" (swing head) to work (at least in my imagination!) you'd need the two point support that you suggest, but you'd also have to ensure that the sliding friction is very low, or the friction would tilt the head. To get a constant vertical depth of cut, the rider(s) needs to be very close to the point of cutting. My guess is that you might create more problems than you solve, but there's only one way to find out for sure (for the small cost of $15!).

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

http://www.goreguitars.com.au

[quote="... To get a constant vertical depth of cut, the rider(s) needs to be very close to the point of cutting. My guess is that you might create more problems than you solve, but there's only one way to find out for sure (for the small cost of $15!).[/quote]

Would they? I've only just begun to think about this but it seems to me that, since I build with a set dome across the entire surface (with the exception of the middle of the upper bout) and the 2 points of contact are a fixed distance apart then the chord created by connecting the 2 points of contact would always be the same depth below the arc they span and thus yield a constant depth of cut.

I would have to slightly reset the depth between the top and the back, though, since I use a different radius for each.

I hope my explanation for my thinking makes sense (I haven't taken a math course since my sophomore year in college 15 years ago). And, again, I've only just begun to think about this so I might be mistaken in the way I'm visualizing things.

I can sell you the donut. In all binding machines the more accurate the less variables you need so the do nut will eliminate some of the angle. You don't want the router to move more than needed.

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

I have no problem making the doughnut (have lots of scrap delrin laying around the shop that I bought on the cheap a few years ago). I was just thinking of an improved design. The tower keeps the side of the cutter parallel to the sides of the instrument but the tilting carriage and 2-points of contact would keep the bottom of the cutter parallel to the top surface and keep the channel from having the very slight U shape as it does with the single-axis motion.

...admittedly it may be an improvement for an issue that isn't a real problem in practice.

It depends on how you go around the corners (as I'm imagining this). If you keep the line of the twin riders tangential to the side and have a tilt mechanism, you should keep more-or-less constant vertical depth of cut. But one of the advantages of bearing guided rabbeting bits (bit of an assumption there, that that is what you plan to use) and a single close point of contact (and no tilt mechanism) is that both horizontal and vertical depth of cut remain pretty constant irrespective of the angle of rotation that the job approaches the bit. With a two point support, even with a tilt head, if the job changes its approach angle, one point of the support is going to climb the dome and alter the vertical depth of cut (as I'm imagining this). There might be a way around that if you have a two-point guide on the sides, too, that kept the "top" riders tangential....

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

http://www.goreguitars.com.au

what did you not like about the hand held unit?????

_________________
MK5acoustics.com

I can't remember what this method is called(photo from Collings Guitars), lets you steer the body tangent as you go around. It's a little balacy but works well.

I have seen this set up (where the router is mounted horizontally low and the guitar is "dropped" onto the bit and spun by hand) at Taylor and at another factory tour. I've never heard of anyone in a small shop doing it. The guys at Taylor were routing binding channels accurately in about a minute and half.

I've been tempted to recreate this setup. Does anyone know why this isn't common? Is there a not obvious problem? It seems simpler than an elaborate rig with a parallelogram, a lazy Susan, drawer slides, and a guitar cradle with six adjustable sliding shelves.


Sent from my iPhone using Tapatalk

The concept works great with bearing guided bits -- straight bit with captured guide is a little tricky since it is important to keep the cut apex perpendicular to the perimeter. A simple matter if the body is laying flat -- not so much if balanced on the guide bearing.

_________________
Ken Cierp

http://www.kennethmichaelguitars.com/

FWIW...here's ours. It's compact and wall mounted. It's very stable as a result, no vibration or chatter.

Every cut has it's own router for efficiency, just swap routers and go. Routers are held in using the edge guide system that came with the router. The sled has markings for different models.

The shoe or whatever it's called is a piece of gently rounded and tapered scrap wood CA'd in place. I thought the plastic donuts would be better, so I got one and did not like it. I prefer the lowest part of the shoe to be as close to the cutting edge as possible. Which is why ours tapers upwards as it gets farther from the bit.

I like your design, Ed. Hope you don't mind if I do a copy of it! Did you use regular full ext. slides? I'll see about getting extra base plates for my Ridgid trimmer, or make some myself.

Alex

_________________
"Indecision is the key to flexibility" .... Bumper sticker

Mine is more or less a Ribbecke design, without any counterweights. Poach as you see fit. Just regular cheap drawer slides are fine. You only actually use a few inches of travel. One thing to note is the bolt above the router holder. It let's you fine tune the vertical ness of the router...

I have used the Ribbecke design for 12 years and like it. I modified the shoe making the contact area smaller and added a rope and pulley counterweight.



I got a double parallelogram device like Arnt uses from a British guy and it is a work of art but I like the tower better except for tight cutaways.

http://www.luthiertools.co.uk

I don't think you have to get too fancy with the tower design if the contact area of the shoe is small enough. I do like a counterweight so the full weight of the router is not on your guitar.

_________________
It's not what you don't know that hurts you, it's what you do know that's wrong.

FWIW, I tried the tower type cutter with a bearing guided rabbit bit and found a few shortcomings, the lack of control of depth of cut, i.e. changing bearings, keeping the guitar vertical to the bit in a cradle , cutting in tight quarters, having to shove the guitar to the bearing to start the cut, difficulty in fine tuning cuts like the purling at the tail end etc.. , after doing some searching it seemed to me ,IMO, that a handheld cutter was the way to go, using the sides of the guitar for the guides keeps the cutter vertical, an adjustable guide so any size cut could easily be made and some difficult cuts refined with a fine tune adjustment, not to mention not having a big jig to store, The only downside I have found so far is it takes a little practice, but as soon as I became comfortable I found I could fine tune cuts to make the binding and purflings fit flush in the pockets, its much easier to sneak up on a cut than be stuck with a bearing for depth of cut...

_________________
MK5acoustics.com

For obvious reasons I totally agree with Wes

_________________
Ken Cierp

http://www.kennethmichaelguitars.com/

Whatever gets the job done. I find the plug and play router switching to be a huge advantage...

I LOVE your jig. Did you make it yourself?



Sent from my iPhone using Tapatalk

Yes its a homemade unit, I do have a small cnc that I used to make the jig, however it could be fairly easy to make one out of wood , it uses a 1/4 inch bit for cutting.

_________________
MK5acoustics.com

I think Ken Cierp sells a simular jig made of wood

_________________
MK5acoustics.com

I'm not liking handheld jig just because if you tilt the router just a little bit (which is EASY to do) you will have done irreversible damage to the guitar.

_________________
Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

not really, it just lifts the bit out of the cut, but like any jig if you get sloppy it can make a mess of things, the jig uses a 1/4 inch downcut bit not a rabbiting bit so only a small part of the bit protrudes from the jig which is a little safer as well..

_________________
MK5acoustics.com

Ken also has a small router table for binding, which is what I use most. I have not tried a hand held jig, but I do have the Ribbecke style and the Williams style jigs. They all get the job done, but I feel more comfortable using the router table.

Perhaps if the jig is not properly designed --- KMG sells both adjustable (1/4" bit) and bearing guided bit hand held binding routing attachment. These devices are so fail safe we include them in our complete Success Kit packages designed for the absolute beginning builder. There is also an all metal version very similar to Wes' that sells for about $275 -- so again its about the design.

_________________
Ken Cierp

http://www.kennethmichaelguitars.com/

Yeah, in the 10 years I used the one I made I never had any real issues with tipping...not to say that you don't have to pay attention to what you're doing and how you approach things but I never damaged an instrument.
It worked well but it's finally starting to show its age, some parts are getting a little worn out (mine was made solid hardwood).

Rather than make a replacement I just decided to try something different, something that might take a little less thought and time.

As to my original thought/question, I think I'm gonna skip the swing/tilt feature. After giving it some more thought, I think I could make it work well...but it would be a touch more complicated than I'd originally thought and not really worth the effort.