Official Luthiers Forum!

Hello,

I'm back again with another question about the neck angle jig. I'm using a jig I built from Robert Obriens video on YouTube.

I have used it a couple of times with fair results but on one attempt I found I had to "floss" quite a bit to get the gap closed when fitting the neck. On all attempts to use the jig I've had the neck angle set and then had to cut the bottom of the neck on an angle in order to get it to sit flat against the bottom of the router template (let me know if I need to take a pic of this to be clear). In all cases where I had to cut the bottom I had already started to shape the base of the neck when tapering it for the first rough taper which means it is no longer square. I've had a hard time cutting the bottom of the neck and keeping things square.

The question - Do you guys typically keep the neck block square and then cut the angle needed for the neck jig (if any) and then do a little shaping? It seems really easy for me to get the bottom of the neck block so out of square that after cutting the tenon the remaining neck base is askew.

Hopefully that is clear, if not I can take some pics. Or, if there is a FAQ or something on the angle jig that would be great.

Thanks!
Brad


Sent from my iPhone using Tapatalk

_________________
Insta - https://www.instagram.com/cbcguitars/
Facebook - https://www.facebook.com/cbcguitars

Not very clear...pics would help.

I'll do my best to explain what I'm doing. I mostly want to know how other folks go through this point in the build and if my expectations are correct or not.

What I was trying to describe in the first post was when to deal with the angled cut across the bottom of the heel in order to get it to sit flush in the neck angle jig.

First, I'll show the way I *think* it should go in order to keep everything square:

1) Use the guitar body to set the right angle at the saddle location. I'm using Robert O'Brien's video for this and he recommended 3.5 mm. Once the angle is set I put the neck in place. The gap at the front of the neck (fretboard side) is about two mm as you can see in the picture:


2) I mark a line that goes 2mm at the back of the heel up to nothing on the front of the heel (fretboard side). I then set the miter to ~1.5 degrees to make the cut.



3) After making the cut the heel sits flush up against the template.


4) After routing the heel I have this:


5) Leaving the miter at the same ~1.5 degree angle I lower the table saw blade and cut the excess off of each side, right at the 12th fret line (I'm building a 00 12th at the body).


6) This is the result (understood about the grain in the heel stack, this is just a test).


My questions:

1) In the Robert O'Brien video he talks about pre-tapering the neck and cutting away some of the heel at the angle of the final neck shape. If I do that first before cutting the tenon I had a hard time keeping the cut that I make in pics 2 & 3 square. Is the method above in the pics OK as well? Seems fine to me, but I'm curious if there is a step later that the pre-taper will come in handy?

2) How do other folks do these steps?

3) Should I expect the neck to have zero or very little gap right off the bat? It seems I have to do a lot of th3e "flossing" that Robert talks about in his video. Sliding sandpaper between the neck and body to get things contoured into shape.

I mostly just want to make sure my expectations are correct. Otherwise I start obsessing over little things and get myself into trouble.

P.S. I got an iPhone for Christmas, so hopefully my pics will be better now!

Thanks!
Brad

_________________
Insta - https://www.instagram.com/cbcguitars/
Facebook - https://www.facebook.com/cbcguitars

Not sure if this will help. I use a different method to cut mine but the end result is the same.

I don't cut any taper in the neck until I am ready to do the final shaping with the heel cap glued on for the reasons you have mentioned. A tapered neck doesn't lend it self well to being cut with power tools.

At the stage you are at right now, if you 90% shape your heel, It makes life much easier. Less wood to remove.

I would think most hand builders get some sloppy fits off the saw or whatever your method of cutting the tenon. I do from time to time and I find a fair size sanding block with 80g can speed things up by holding the neck on your bench and removing wood where needed with the block. I find it gets me close faster than flossing. Especially if you need to change the neck angle slightly or the centre line line up.

Hope this helps some.

Best of the Season!

I thought the "whole idea" behind this type of fixture is to make one set of cuts so the angles match? If not I guess, I am missing something regarding there use/or the need.

_________________
Ken Cierp

http://www.kennethmichaelguitars.com/

Brad you are doing good work. There are a couple of ways to get the angle depending on your tools. Some us a sander. By just standing up the neck on its heel and applying more pressure to the side where you want more taken away will work. It takes a bit of practice but lots of us do it. I have an angle gauge on my sander so I can cut it with my bandsaw close and then sand perfect. Another way is to use the blade tilt on your table saw. It won't go all the way through and you can finish with a hand saw.

I just though about what Ken wrote. And of course he is correct. If you set the neck so it is at the desired angle and cut the tenon, your angle will be as desired. But the butt end of your tenon will be a bit too long at the heel end. Cut it off or sand it and you are done. No table saw work necessary.

_________________
Ken

Thanks, all.

Ken M, thank you for that bit of wisdom there. I took Robert's statement in the video of "make sure the bottom of the neck is flush" as the only option. Which is why I resorted to tapering the bottom of the neck first before routing. To make sure I know what you mean exactly....

1) Place the neck in the jig while the bottom is still square. Ignore the gap for now.
2) Route using the jig as usual but be sure to set the depth of the bit to be the 12th fret line (or 14th, etc...) on the fretboard side, which may be longer than your targeted 7/8" tenon.
3) After routing, the tenon on the fretboard side will be 7/8". The tenon on the butt end will be longer (should be 7/8" + the gap in the fretboard side before routing).
4) Trim / sand the butt end of the tenon to level off the whole tenon at 7/8".

Does that sound correct?



Thanks!

Thanks again for all the help.

Brad

_________________
Insta - https://www.instagram.com/cbcguitars/
Facebook - https://www.facebook.com/cbcguitars

Yes, that will avoid the double work as Ken stated. I would not route that in a single pass in case you were going to try that. Max depth per pass is usually half the diameter of your bit. 1/4 for a 1/2 bit.

_________________
Ken

Thanks for the confirmation. I've been doing it in 5 or 6 passes because I have a Bosch colt in a plunge base and it binds easily.

Thanks for the help!


Sent from my iPhone using Tapatalk

_________________
Insta - https://www.instagram.com/cbcguitars/
Facebook - https://www.facebook.com/cbcguitars

When I was doing tenons, I more or less followed the same steps. Are you concerned that the angle of the heel and neck surface isn't a right angle? It generally shouldn't be...

No Ed the LMI jig is designed to set the neck heel in a position as to route the cheeks of the heel at an angle that projects the fingerboard straight to the correct height above the bridge.

_________________
Ken

The funny thing is that the author of the thread, Brad, actually took the effort, time and expense to build a complicated jig to automatically set the neck angle and then went ahead and figured out how to do it without the jig.
But now you have a nice jig to hold the body and get the desired result. Robby O makes nice jigs.

_________________
Ken

I doubt that many others do this but I first get close all on the table saw. Starting off with all things square, I can very quickly cut out the tenon on the end of the neck. Then I put it in a simple jig to route the angle onto the cheeks of the heel. So I actually route very little wood. My expectations at this point are only to get in range for flossing and I start the flossing with 80 grit paper. Sometimes, for me anyway, the flossing goes fast and sometimes it takes me over an hour to get the flossing done to my satisfaction.

Pat

_________________
There are three kinds of people:

Those that make things happen,
those that watch things happen,
and those that wondered what happened.

So let me get this straight. Some of you are cutting your M&T using a neck angle jig and you have to do zero final adjustments? I will admit I can get better at this, and the amount of adjustments I currently make are minimal, but I still have to fine tune. I use the Luthier Tools gen 2 jig.

What I'm saying is I'm not surprised the OP has to fine tune based on my experiences.

Mike, what do you mean by fine tune? I am curious.

_________________
Ken

Final fit. Mostly, I assume it's due to subtle inaccuracies in the general geometry of the box that were not, or could not be, accounted for in the setup process. That's why I say I can get better at this. I've only done 6 with the jig. It is a world of difference better than how I used to do it. I still have to sand relief into neck at the tennon. Jig does not do that.

I thought most of those templates had you routing off all but the tenon, so I'm surprised you had to deal with the rest. Ya, I would just make it a little tall, then level the tenon up on an appropriate sander.

Mike, I don't think they are talking about final flossing, but rather the initial hogging.

_________________
Pat

Al mentioned by Pat above, that jig needs a bigger opening so that you can rout everything off. I built my jig with the Stew Mac acrylic templates that allow you to do that.

I Start with a collet in the router base for initial hogging off so I can do shallow passes and then switch to a bearing guided template bit for the final cuts.

The end of the tenon needs to be squared on the belt sander as mentioned.

Here is one way to do the initial heel profile.

http://www.kennedyguitars.com/heel-prof ... empla.html

As usual a million ways to do stuff that all work. I know a lot of folks use the table saw for the whole operation.

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

Pat, the OP definitely mentioned flossing making me think this was a final fit issue.

Ok thanks A lot of things going on with the up down angle, the left right angle and the gaps.

_________________
Ken

nice jig Terence!

_________________
Ken

I think (don't know) that you might be missing a piece of the jigsaw.

00s, at least the ones that I've built, are curved in the upper bout where the neck fits. That means that the cheeks of the tenon where they face onto the sides of the box need to be undercut. The typical undercut angle is ~5 degrees. If you rout the tenon as you have done it is impossible to rout the undercut required, which means it has to be cut separately. If you leave the heel as a rectangular block and do all the angle setting with the bottom of the heel at full width, then do the undercut, then taper the heel, the neck angle changes (it becomes more set back) because the root of the undercut is further into the neck material than the outer edge. Difficult to explain, but you may be able to see what I mean in the picture, with the white line showing the eventual heel taper:


That would be why Robbie is saying rough carve the heel shape first, then do the angle set, if that is what you meant here:

Cumpiano relies on this heel tapering, which in conjunction with the undercut gives him most of the neck set-back required.

If you do all the cuts on your table saw, its easy to get the 5 degree undercut and the tenon cut, then rough shape the heel, then do the angle fitting. The cheeks of the neck tenon contact the box sides as a "knife edge", so flossing goes real quick because you're just taking the edge off the knife to create a small land to rest against the sides. Normally I do all these cuts on a bandsaw, trim the surfaces with a low angle rabbeting plane (a shoulder plane would work fine) and can get the basic geometry real quick. One can't expect it to fit exactly, straight off the saw (whatever type you use) so I find a shoulder type plane pretty much essential for the job. Certainly a lot faster than sanding. The flossing just creates the land so that the finish isn't chipped out by the "knife edge" on the shoulders when all bolted up.

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

http://www.goreguitars.com.au

Thanks again, folks. A lot of good information here.

Trevor, I used your method of undercutting the base of the neck on a second neck that I'm working on. The results were much better. Half the time spent flossing I would guess.

Terence, I totally ripped off your jig and I think the results were pretty good. I flipped the bearing on the robosander and make a small table with registration dowels. A question though, do you typically just slide the base of the jig around on the drill press table to move the neck in and out of the sander? That is what I did and it worked, just curious if there was a better way.

Here are some pics of the neck bolted onto the body:






Next step is to attach the fretboard and finish shaping the neck!

Thanks again for all the help!

Brad

_________________
Insta - https://www.instagram.com/cbcguitars/
Facebook - https://www.facebook.com/cbcguitars

I would be really happy with that!
Yea Tarence has a nice jig there for shaping the end of the heel.

_________________
Ken

Purple heart and ebony.......mmm tasty!

_________________
Pat