OK you wise, older Californians (I am thinking of Mr Ford and Mr Hostetter here), and others. Can you advise me on this? But, first I need to tell you a short story to explain why I am think about it.
A while ago I built a small jumbo (my 3rd guitar), and it was my first attempt at building a cutaway. It all went pretty well and it is a good guitar, except for one problem. When I got to the stage of fitting the neck and setting it up I found that the neck angle was wrong. The neck block is rotated a bit forwards, so that when the neck is fitted a straightedge running on top of the fretboard projects well under the top of the bridge. It has a bolt-on neck so I compensated by taking wood off the heel, like you would in a neck reset, but it would need quite a lot (too much) taken off to get it completely right. I bought a bit more angle at the bridge by shaving it a bit lower, fitting a low saddle, and I also kept the top flat by using a bridge doctor. I ended up with something that is a workable, but not ideal.
I realize now where it all went wrong. When gluing the sides to the neck block I did not pay enough attention to getting it square in both dimensions. I hadn't done this step with a cutaway before - where you are gluing onto two faces of the neck block at the same time. I didn't pick up on this mistake straight away, so after I glued the top and the back on I ended up with a box that wasn't square at the angle between the top and the neckblock. I learned an important lesson there! And the couple of guitars I have built since have been fine.
Anyway - I now want to see if I can fix this thing up. If I "slipped the back" I could pull the neckblock into the correct angle - but I guess that I would also need to release the bond between the cutaway side and the side of the block. Sounds tricky. In the days when this maneuver was more commonplace did you ever do it for a cutaway? What advice do you have for me?
Mark I'm no longer a Californian but once was and I am not all that old either but since this has sat here unanswered for a while I hope that you don't mind if I take a crack at your questions.
Seems to me that what you wanna do is more an approach to addressing symptoms than the root problem. Things like shaving bridges, lowering saddles, considering slipping a neck block, etc. may not be necessary.
You mentioned that you would have to remove too much material from the neck heel so you didn't want to go that route. What my question to you is how much material would this be and what is the shape of your neck heel?
I'm sitting here looking at a very nearly pre-war Martin (pre civil war) from the 1870's and these puppies have an ice cream cone heel - a very eloquent design that eventually tapers to nothing. With this said it may be possible for you to remove more material from the neck heel than you think that you should and if this is the case it would be far easier than other approaches.
Just a thought.
If this is a bolt-on neck it sure seems easier to take material from the heel than to slip the endblock. If the contact point needs to move up, say, 1/4 inch you'd only have to remove about 1/5 that amount from the heel, or about 0.05" (more or less, depending on your scale length and heel depth).
To answer your question, though, the back is released from the neckblock and sides; the side is not released from the block. You would have to release the back to about the widest part of the upper bout on both treble and bass side. Disclosure: although I have been a guitar repairer in California for 38 years, I have only used this technique once, as a last resort. It certainly never has been a common procedure among the repairers I know here.
I'm with Greg. Offhand I'd say that the potential for damage in trying to slip the neck block far outweighs any consideration of how you reestablish the neck angle. If you can't take enough off the bottom of the heel, you can shim the whole business, and suffer the cosmetic change you have to make to the heel with colored lacquer or whatever.
OK, thanks guys. I guess that what you are saying is that it doesn't matter how I re-establish the neck angle. If I have made a box with a crooked angle I just have to make a neck with a corresponding/complementary crooked angle, and I will have a working guitar. If it looks a bit unconventional, I will write it down to experience and go on to make better guitars in the future. I will tell all of my Australian friends that it is not a mistake - this is how they used to make guitars in California.
BTW California is not the only one to lay claim to this method of slipping the neck block.... It lives in infamy.... in many states as it is unaffectionately referred to here as a Michigan neck reset....;) But if you California guys want it I have no objection....
Hey Mark- I was never from California or lived there for very long - however- when I made my very first flat top guitar I made the mistake of not making sure that the neck block in the body was square to the form and ended up making as new neck and fixing the neck angle to accomidate the body-- I still have the guitar and it plays just fine-- good thing too or I would have put it in the burn pile== best to you in fixing your own problem----