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Been considering getting either one of these jigs and would be interested in opinions please.I'm drawn towards the Simpson but find one thing about it confusing.First off let me say i mailed Jon a few times and found him very accommadating but am still confused and didn't want to try his patience.Ok here's the confusion,I watched the tutorial and was ok untill the point where Jon sets the neck angle he says to have the straight edge touching the dummy fingerboard and the top of the saddle,surely it should be just above the top of the bridge,say 1/32" as the straight edge represents the continuation of the fingerboard.As i see it this would result in too great an angle with the fingerboard heading towards the top of the saddle.I'd be gratefull to hear from anyone who uses the jig to clear this up for me.Thanks all Roby

Thanks for the reply Todd,i know how these jigs work by measuring the gap at the bridge location ,my point was that by having the straight edge touching the dummy fingerboard and the top of the saddle i.e 1/2 inch off the soundboard the neck angle would be too great.The way i see it this would result in raising the saddle height by 1/8 inch resulting in a finished saddle of 1/4 inch above the bridge and a string height of 5/8 above the soundboard which seems far too high.Does this make sense or have i got something wrong here.Thanks again Roby

Thanks Todd glad to know i'ts not just me missing something , 0.080" is about what i aim for aswell ,would be interesting to hear from anyone who uses this jig to clarify this.Tried searching for the woolson plans but can't find them.Thanks again Roby

I was lazy and just purchased Simpson's jig. Simpson's instructions seemed odd to me as well, and I've been using about the same process on the bare top as Todd it sounds like. Overall, I like the jig. Simple and pretty foolproof, which is very important for a fool like me.

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Aaron Craig

Ideally, and depending upon your geometry and how your tops pull in once strung, an un-fretted fingerboard should over-shoot the bridge without the saddle by .015 - .020", thereby getting a rise of .55 - .063" once fretted. The top pulling in will give you proper set. I'm not sure why Jon puts the saddle in as that would, as you point out, overshoot the set by a minimum of an 1/8".

I'm not thrilled by either design (I haven't seen Paul's original design, only Robbie's). In the case of Jon's his body vise, while compact, runs into problems with cutaways in a way that the Woolson/LMI jig does not. Robbie's unfortunately cavalier approach to building the LMI fixture as demonstrated in the videos is problematic. We build tools to be accurate. We shouldn't be encouraging folks to allow errors in the fixture as that will cascade throughout the process. It's not that builders shouldn't understand that they'll need to adjust for occasional errors, but we should encourage folks to make sure everything is perfectly square, perfectly aligned.

I cannot comment on the dovetail as I haven't used it, so I'll keep my comments to the mortice and tenon.

1) The templates, used as recommended, end up with an oversized tenon that is fine for guitars with a Jazz heel, but not for narrower French heels as found on Martin's. You'd have to have a fat heel cap. I used a smaller bit than the recommended 1/2" bit which gave me a still oversized tenon of .775" The templates should be sized for a .75" tenon to allow for traditional guitars; I also didn't find the templates to be as accurate as I'd like and found I had to rack the templates for the tenons because I found that their edges weren't perfectly parallel with the guide edges.

2). For example, although you don't need the room, his design instructs a cutout in the top of the fixture that is overly wide for the actual cuts that will be made. Consequently, the fixture ends up lacking the support structure necessary to adequately register the body against the underside of the fixture. This is particularly problematic with cutaways which can fall into the void on the one side.

3) His back body clamp is flat, rather than radiused and tapered. Guitars typically have a 15-20' back radius, and a 3/4-1" end to end taper over a 19-20" body. That clamp should be arched and angled to properly accommodate that angle so that the clamp is putting pressure across the head block rather than just past it into the back where overzealous tightening or accidental bump might crack it.

4). Most modern builders are not building perfectly flat. There is no accommodation in the design for this and consequently a body clamped in the fixture cannot register square to the sides and ends up racked giving a mortise of inconsistent depth from one end to the other (one could shim, but then you're introducing the possibility of more error). Putting a corresponding bevel on the leading edge of the platform would cant the body clamp facing out to take into account this angle.

4). There should be a clear centerline finder on the fixture. I mortised a notch in the back of the front body clamp face to accept a 2x16" piece of acrylic with a centerline scribed into the back. This is to be sure that the body is perfectly aligned both at the top of the body as well as along the centerline. Having the body centered at the mortise isn't the same as having the cut aligned with the centerline of the body.

7). The alignment fixture for the neck should be a spline like Jon's not two pins. Minor variations in the slot edges, particularly when routed, when paired with two pins can create alignment error. Better to have a spline that will average any error and help make the cuts aligned with the center of the neck.

That's what I remember for now, having gone through this this summer. It's incredibly important with the LMI jig to make sure all your cuts are perfectly aligned. We're trying to make fast and accurate cuts, not create more work for ourselves. Many of the folks here are building their first instruments and have little experience in woodworking to begin with. We can do better.

Thanks for the help all , i do use a spanish heel, would this be a problem with these templates or would i just have to use a smaller guide bush/cutter? Still Like to hear more from anyone using these jigs .Thanks Roby

Even with a smaller bit (same template guide bushing), the .775" mortice is barely narrow enough for a narrow Spanish heel. At this size, you'll have a .875" wide, perhaps a tad narrower heel at the heel cap.

Found this thread from not too long ago while searching for plans for the Woolsen jig. Did anyone find a source for the plans? LMI wants $115 for plans and hardware

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Kyle

I have the Simpson jig but but find the process more trouble than necessary , and if care is not taken especially working on a cutaway you can make a mess of things, and yes the way he sets the angle does not work, which will result in a incorrect heel angle plus its hard to get the center line dead on when using a router to rout the mortise. I have gone back to making the neck block with the mortise built in making sure it is glued in straight with the centerlines lined up, then transfer the neck angle to the heel and sand on a disc sander getting the angle and centerline set properly, then cut the tenon using Cumpiano's method on a table saw....process is easy , accurate and no jig to keep up with...

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MK5acoustics.com

That's what I was thinking.

I need the space that a jig would take up as my space is limited.

I guess that's not the point of the OP though, as he wants to use the jig, but was confused by the directions.

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Old growth, shmold growth!

I think I remember simpson chiming in on this thread. Am I imagining things? Anyone else having trouble with a cutaway on this type of jig? I also got the sm templates and was Miffed by the .05 slop. Think I will return those.

Sent from my GT-I9300 using Tapatalk 2

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Pat

Hi Roby

I had the Simpson Jig and was more than a little confused about the method of setting the neck angle. Finally just came up with a measurement that got pretty close and did it my own way. I decided to try the LMI jig and made some modifications to it. First I used a slot instead of the 2 pins, to align the truss rod with the jig before cutting the tenon. I use both Martin style and hot rod truss rods so I made the slot 1/4" and used shims in the actual truss rod slot to line it up. I also put a back radius of 15' in the back clamping block and covered both clamping blocks with cork, I also built a sliding bottom bracket that holds the guitar body. You don't have to tighten the clamping blocks too tight with this attachment - picture below. I made an alignment board that gets the body lined up with the jig down the center line so that my mortise is aligned with the guitar body - also picture below. I'm pretty happy with the LMI now but i think the actual neck angle only gets you close and you have to do some fitting to get the measurements you are looking for. Still pretty good.

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guitarsbygiltzow.com