Filling Some Neck Gaps

Friday, June 12, 2009

Between work and some much-needed early summer-time chores, I did not get a lot done this week - but I did get a little.

After posting last Sunday, it dawned on me that I had made yet another mistake - while gluing the neck to the body, one of the things you need to do is to locate the neck at the proper depth with respect to the top of the head-block. Now this might seem pretty straight forward, but I can assure you it CAN be messed up. It’s not perfectly clear from my photos, but the head-block and top of the dovetail in the neck are in different planes - the neck plane is 6 degrees out from the top of the head-block. This means that, at best, only one edge of the two will line up while the other will be offset - no big deal provided that you align the correct edge. So which is the correct edge? The back one (closes to the tailblock - and even that is not EXACTLY the correct one) - and here is why.

The plane of the fretboard on the neck has already been established when it comes time to glue these two pieces together. The top of the head-block has not - it is flat with respect to the body. Once the glue in the dovetail joint dries the head-block needs to be sanded to match the fretboard plane. Now obviously (when your smart enough to think about it in advance) you need to align the neck so that all of the sanding is done to the head-block. I did not do this. I aligned it so that the top of the head-block was below the fretboard plane which, had I done nothing to correct it, would have meant creating a new plane for the fretboard. Not a good idea.

So what I did was to cut and add a thin shim (made from a left-over piece of maple side-wood) that matched the outline of the head-block. This, once glued to the head-block, I was able to sand it down to match the fretboard plane. Since this is located such that it is going to be almost completely hidden from view and then stained so dark that it will be almost impossible to detect, I feel pretty good about this fix.

Now, as I noted in my last post, I also needed a shim on the back of the neck. Just like the one I did on the front, I created a shim using another piece of maple side-wood and glued it to the neck. After sanding it to match the contour of the neck and the plane of the back, I think it looks pretty good, too.

I’m afraid I am not going to get to work on my mandolin next week at all (work, work, and more work), so (for all my followers) I apologize. I hope to post again in a couple of weeks.

Neck Joint Cutting - For Real

Sunday, June 7, 2009.

Well I finally cut my neck joint - this was the step I feared the most (so far). Having never attempted a dovetail joint before, I was just new I would mess it up to the point that I would have to start all over. Fortunately, it looks like this won’t be the case - at least not for this reason, anyway.



Cutting the body side of the joint was really straight forward since the design has this cut square with the body. Since I have yet to attach the back, the rim sets nicely on my bandsaw and once the shape was transferred from the template, it was as simple to cut as you could want.

As you can see from the photos, I ended up needing to install a shim on one side of my dovetail. This is a piece of the same maple veneer I have used elsewhere and ended up being necessary once I got finished trimming and sanding the curved section of the joint on both the neck and the body. The veneer turned out to be almost exactly the right thickness right out of the box. All I did was to cut a section the right length and width, glue it on to the side of the joint and let it set up before attaching the neck.

You will also notice that there is a spacer that has been attached to the head-block. Because the fretboard will eventually extend over the body but not be attached to it, there needs to be a support onto which it will attach. Furthermore, the design has a binding strip that matches up to with the 15th fret (I will be installing that pretty soon) and yet another extension that will act as a support out over the body. This piece fills the gap between the neck joint and the 15th fret that would otherwise be there. If this is not all perfectly clear, I imagine it will be once I get that part done and some photos up. In the mean time, here are some pictures of the joint in neck.




And finally, here is the joint glued together.






In addition to the shim I talked about earlier, I added a very thin shim to the opposite side of the dovetail in the back. I installed this shim as my last step just after the joint was made up. It acted to really tighten the joint up and to add just a tiny amount of twist that I needed to square the plane of the fretboard with the body.

When you look at the back of the joint, you will probably notice that the base of the neck is set back a bit from the body. This is a result of my over zealous sanding way, way back when I was first shaping the neck. I realized pretty early that this would likely be a problem at this stage, but figured it was a small enough issue that I would go ahead with it rather than to make a another neck. Since I intend to finish this part of the mandolin quite dark and this is not a critical piece, I plan to make a maple shim to fit here.

This can be our little secret.

Now to let the glue dry and get started working on the rest of the fretboard.

Jig for Cutting The Dovetail Joint

Saturday, May 31, 2009.

In researching how to cut myself a dovetail style neck joint, Mr. Siminoff shows a jig for holding the neck at the proper angle when using the bandsaw. Unfortunately I find that he does not give any indication just how to build this jig, only a couple of photos of his in use. So, the last couple of days have been focused on making this jig and I think I’ve got it. Here is what it looks like and how I made it.

This jig has three important surfaces - the base, the flat that the peghead is clamped to, and the ledge where the base of the joint rests. The base and the ledge are pretty easy to figure since they are parallel to one another, but he flat for the peghead is a bit more tricky. Since the goal here is to hold the back of the neck joint perpendicular to the surface of the bandsaw table, this flat needs to be cut at an angle that combines the 6 degrees plus the angle of the peghead with respect to the fretboard. This means I had to find a way to layout, cut and then verify that the fretboard plane was, in the end, held at 6 degrees off of vertical.

The first thing I did was to I created a jig block by cutting up a 1x6 of hardwood and gluing it back together to create a 6x6 block approximately 12 inches long.

Next, I did some trigonometry to determine the rise and run of a 6 degree angle. This, I calculated, corresponded closely to 1 inch of rise for a run of 10-7/16 inches. Knowing this, I had a way to verify that I really had a 6 degree rise.

Then, rather than try to calculate what the angle of the flat needed to be, I chose to approximate this angle by holding neck and peghead in the approximate location and sketching a line. Once I was pretty comfortable that my sketch was close enough, I cut out the rough shape on my bandsaw and rough-sanded the peghead flat on my belt-sander.

Now that I had something to work with, I needed to be able to clamp the neck and peghead to the jig. For this, I chose to drill four 7/8” diameter holes in the sides of the jig. These holes are big enough to allow me to insert the fixed end of my small C-clamps and clamp without getting in the way.

With my peghead now clamped in place and the heal of the neck joint just clear of the ledge, I was ready to verify my angle. This was done using a flat scale I have and a framing square.


By laying the scale on the fretboard and holding the framing square against it, I am able to make a height measurement at both the “zero” position (in this case, at the edge of the peghead veneer) and then at the 10-7/16” distance. Since my goal is to determine an angle, not an actual distance, I don’t care what the actual measurements are, only that the difference is close to 1 inch. As you can see from the two photos above, that is what I was able to get - just under 3" in the first photo and just under 4" in the second one (the first time I measured I was a shallow, so I took the jig back to my belt-sander until it was good).

Now that my jig is ready, all I have to do is layout my dovetail, create a spacer block to mount to the head block, and work up the nerve to make the dovetail cuts in both the head block and the neck.

Meanwhile, here are some more pictures of the neck clamped in the jig.






And finally, here you can see that the neck joint and jig will just be able to fit into my bandsaw when it is in its most open setting. Thank goodness. I was afraid for a while I was going to have to shell out some big bucks for a larger bandsaw (or cut the joint completely by hand - I really did not want to have to do that!)

Later.

Neck Joint Cutting - Almost

Thursday, May 28, 2009.

Well, I am rapidly approaching the end of May and it occurs to me that I have been working on this now for just over five full months. As I look at what I have to show for the time, it doesn’t seem like much. When I look back at this blog, though, the road has been pretty long and I have already learned a bunch more than I ever expected.

I’m good with it and I can only hope you are, too. So lets keep going.

I am a bit disappointed in how little I have been able to get done in the last several days, but its not like I have been sitting still. I glued my soundboard on to the rim and spent a great deal of effort to create a jig for cutting the joint in the headblock where the neck attaches. My disappointment comes from the fact that for all my work, I am not going to be able to use the jig I made but will have to cut the joint differently than I had planned, but I’ll get to that later. At the moment, I want to show you something I came up with.

A couple of annoying little problems I ran into when using the hot hide-glue were that the glue cooled down too quickly and I was having to heat it downstairs in the kitchen and run with it upstairs to use it. When it began to cool off, I either had to run back downstairs again or stop where I was. Not fun. Then one day as I was browsing through the posts on the Mandolin Cafe, I ran across a thread where others were sharing how they dealt with this and other hide-glue problems. One of the things that caught my attention was how some folks make up their glue into plastic squeeze bottles and place steel nuts in with the glue to add weight and hold heat. What a cool idea. So that is what I did.

For my bottle, I took a nearly empty Elmer’s Glue bottle, washed it out, and poured in my heated hide-glue. I then put in four nuts - small enough to go through the mouth of the bottle but big enough to not interfere with the glue reaching the nozzle.

Now that I had an improved glue delivery system, I needed an improved heating system. While I could have purchased a single electric cooking eye or one of the glue pots you can buy at Stew-Mac or LMI, I did not want to spend that kind of money on it. Instead, my wife happen to find a “personal coffee heater” at a yard sale.

Using this, along with a glass bowl of water, I no longer have to run up and down the stairs. This is the rig I used to heat my glue when it came time to glue the soundboard to the rim and I must say I am very pleased with how well and quickly it works.

So, once the glue on my soundboard assembly had dried, it was time to focus on the neck joint.

In Mr. Siminoff’s book, he details two methods for cutting this joint; one method is his own development (the one I settled on) and the other is the classic dovetail joint. In order to cut the Siminoff joint, you need to create a jig that both elevates the head block to about a 6 degree angle and allow it to rotate in both directions so that you can cut a “V” joint with your bandsaw. Early on, as I looked over my bandsaw and the materials I had on hand, I knew that creating this jig was going to be a challenge, but I figured I had what I needed. Sadly, though, I was wrong. Fortunately I never cut into or damaged anything important in the process of learning I was wrong. All I lost was time.

While I was able to eventually cobble together a jig that allowed me to just get the head block up to the saw blade, I found that I just did not have enough room to allow for the rotation without hitting the bandsaw with the scroll.


Even though I was not able to use it for anything other than a learning experience, I decided to go ahead and put up some pictures of how I put it together. You will probably notice that there are a lot of extra holes and cuts that don’t look planned (they weren’t), but I had to take it apart several times before I got enough clearance to clamp, rotate, and cut even as much as I was able.





So now that I realize I cannot use Siminoff’s joint, its time to learn about and attempt a dovetail joint. From what I read, it looks like this should be one I can cut, it simply takes a lot of touch-feel work to get it right.

I will let you know how it goes.