A neck reset is a common repair for most shops. In order to do the job properly, a thorough knowledge of the materials and processes involved is required. Because the subject is too large and difficult to comprehend in one sitting, I will be splitting the article into multiple parts. In this first part, I will explain when a neck reset is necessary and outline all the steps involved in the process. I will cover the first three steps in more detail including the removal of the neck and fingerboard, as well as preparing the mortise.
MATERIALS AND TOOLS
-Block plane -Chisel -Japanese pull saw with a thin kerf -Another hand saw with a wider kerf -Opening knives -Pencil -Sliding T-bevel -Hide glue -Model maker’s clamps -Various rulers
Reasons to reset a neck
-The appui is too short (The appui is also referred to as overstand). Measured at the foot of the neck, it is the distance from the top plate edge to the fingerboard. A higher appui adds a sense of ‘stickiness’ to the strings, and can also help with the clearance for the left hand moving into upper positions. -The projection is too low (The projection is the angle the fingerboard and neck is set in relation to the instrument). -The poirette needs to be corrected (The poirette is the twist in the neck set that favors the bass or treble side). -The neck is not centered. -The neck has broken out (It’s not enough to simply glue it back in). -The neck length needs to be corrected.
Order of Operations
- Release the neck if it is not broken out already.
- Remove the fingerboard.
- Select, fit, and glue maple and spruce wood pieces into the mortise as needed. This can be done while the glue is drying on other steps.
- Select, fit, and glue a piece of matching wood on the bottom (endgrain) of the neck-foot.
- Select, fit, and glue a piece of matching wood on the back (button) of the neck-foot.
- Fit a new soundpost, if needed. Measure the fingerboard projection by itself and establish the angle at the bottom of the neck-foot. Cut the angle and plane flat.
- Spot glue the fingerboard on the neck.
- Find the corrected position of the bridge by assessing the twist in the instrument body.
- Do a mock neck setting and determine if and where a neck-foot side piece will be needed.
- Select, fit, and glue a side piece on the neck-foot if needed.
- Remove the fingerboard. Plane the sidepiece to match the already established angle of the bottom of the neck-foot.
- Glue-size the bottom of the neck-foot, add pins in bottom and back pieces of the neck-foot, and spot glue the fingerboard back on.
- Set the neck.
- Remove the fingerboard once again, color the exposed bottom of the neck-foot, and permanently glue on the fingerboard.
- Establish the neck heel compass, shape the heel, and blend into the existing neck.
- Color and touch-up.
In this article I will only be covering the first three of these operations in detail and I will address the remaining steps in future articles.
1. Releasing the Neck
Saw a kerf with a very thin saw at the joints where the sides of the neck meet the ribs. I use a Japanese saw that is 0.16 mm thick and has had the very end of the blade cut off allowing teeth to progress to the very end. Most Japanese saws do not have teeth all the way to the end, so you have to be aware of this when purchasing or be willing to modify your saw a bit. 
Start the cut at the joint of the neck, back plate, and ribs. DO NOT SAW THE BACK. Pull the saw through the cut while holding the instrument at the neck heel with the other hand. Let the saw blade run along the thumb of the holding hand in such a way that it keeps the saw blade from nicking the neck. Periodically check your progress by sliding a thin ruler into the kerf. This will indicate any modifications you need to make in the depth or angle of the cut. You should only cut deep enough to allow for the release of the side of the neck-foot. 
As you can see from the photo above, the cut is almost there. When finished, the cut should be very small and conservative. In the case of the instrument below, I had only cut through an older side piece from a previous restoration and had not even touched the original wood. If it is possible to achieve this, then do so. 
When sawing the sides, I cut the left side with the saw in my left hand and the right side with the saw in my right. I find I have more control this way, but for some people it may be too difficult to work with the non-dominant hand. Do what is needed to achieve a controlled cut. Next, I release the button using a classic English style dovetail saw. The kerf on this saw is a little wider which allows for a sharpened feeler gauge to be inserted in the next step. Putting the violin in a stand and stabilizing it against the bench, I saw as close to the button as I feel comfortable. 
Obviously, this step needs to be done slowly and carefully. 
Use a sharpened feeler gauge (.5 mm thick or .6 mm if it’s longer). 
Insert the feeler gauge into the saw kerf with the bevel facing the top plate. 
With the instrument clamped firmly between your legs, use controlled hammer strikes to start splitting the neck wood the rest of the way to the block. 
In order to mitigate any apprehensive feelings, keep these things in mind: -Back up the button with your holding hand so you can feel what is going on and anticipate any issues. -Make sure the violin is held securely between your legs. This method of holding the instrument is safer than others because you can feel what is happening. It is also somewhat flexible and absorbs the hammer blows. -Use very light, controlled strokes with the hammer until you feel comfortable with how things are proceeding. -Move, and tap the feeler gauge at different places in the kerf. Don’t be afraid to leave one spot and come back to it later. -Listen for a drop in pitch when striking with the hammer, that, along with the looseness of the neck, is the indication of the split being successful. -Err on the side of CAUTION!! This next step can be rather dramatic, and best done outside of the hearing range of the faint at heart. VERY IMPORTANT. Before proceeding, make sure there are no open seams. Double check that the neck block is also securely attached to both the top and back. If something is open, you can do damage to the ribs while releasing the neck. Put the instrument on it’s side, tuck the instrument body under your arm, and hold the fingerboard in your hand. With your other hand, give a firm precise hit to the area adjacent to the Cul de Poule (sometimes referred to as the chin of the scroll, It is basically the rounded part at the bottom of the pegbox). DO NOT hit above the Cul de Poule; you could break the scroll. Essentially, if you aim for the side of the nut you will be alright. Gently pull up on the fingerboard while doing this to further encourage the neck to release. 
Here is a video showing me releasing the neck on another instrument. releasing the neck
2. Removing the fingerboard
Use an opening knife. The opening knife is a tapered spatula like knife with a dull edge. Remove the nut and wedge the opening knife into the corner of the fingerboard. Put your thumbs together as demonstrated in the photo. This will keep the knife from breaking lose and cutting the hand that is holding the neck. Apply pressure and wiggle the knife. Keep checking your progress and make sure the knife is not going into the neck or fingerboard. 
Once you get the knife halfway through the neck, you can squeeze the end you already opened making the fingerboard bend over the knife like a fulcrum. Often this is enough pressure to release the rest of the fingerboard. I use a couple different knives for removing a fingerboard, starting the process with a thinner knife and switching to a thicker knife with a more extreme taper. Throughout the process, I soap the knives for a little lubrication. 
3. Selecting, Fitting, and Gluing Wood Pieces Into the Mortise
To begin, clean up the mortise with a sharp chisel, only taking away enough material as necessary and removing any pieces that were in the mortise previously from a past repair. Using maple for the new sides of the mortise, aim for a grain orientation that makes it easier to cut later. The picture below shows the preferred direction of the split. 
I have a little notched area in my bench that makes it easier to plane these small pieces. 
Plane the surfaces so that everything fits snugly into the mortise. Use a chisel to cut and fit the ends to the same length as the ribs. 
Using hide glue, adhere the side pieces using little sticks of old soundposts or chopsticks. 
Next, fit small spruce pieces as top extensions, matching the grain and leaving a little extra height for later neck set mock up. Glue the pieces in place using hide glue and clamp in two directions. In the photo, I use a stick to wedge them out and some small model makers clamps to secure them into the mortise. 
In this example I did not need a piece of spruce in the bottom of the mortise. However, in order to achieve the desired measurements, it is often necessary. In those cases, the grain is oriented in such a way that it is easier to cut later, much like I do for the pieces in the sides. The spruce piece on the bottom is fit and glued first, followed by the side maple pieces. In the next article I will cover numbers 4 through 12 in the order of operations.