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.

Shaping the Peghead

Sunday, May 10, 2009.

Well, yet again, a setback. Looks like I am going to be starting on my third soundboard for this first mandolin.

If it didn’t hurt so much, it would be funny. Ah, but them’s the breaks.

As I was working on roughing and then smoothing this second soundboard, I noticed that the glue joint in the center was remarkably noticeable. At first, I made myself believe that this was simply the glue near the edges and that, as I carved and sanded, it would disappear. Then as I went on, I decided it was just the coloring of the glue since this is a different batch than I used on the first soundboard. Finally, as I began working on getting the thickness graduations uniform, I held it up the a light bulb and noticed some gaps. Dangit. My best guess is that even though I went to lengths to get the mating surfaces flat and parallel, I probably put too much glue on and then didn’t get clamped up well enough (three of my four clamps are old ones that give me fits - I replaced them this weekend).

So - I have my third set of soundboard lumber on order and I am awaiting its arrival. For this effort, I am going to get myself a squirt-bottle for the glue, make sure to apply only as much as I need, and then clamp it using my new clamps. If this doesn’t work.....

Aside from that, I got to work on the neck and peghead some more this week. For this go, I managed to cut the peghead to shape. If you haven’t looked into building an F-style mandolin before one of the features you may not have noticed is that the edges of the peghead are cut perpendicular to the face of the fretboard rather than the peghead. This means that while cutting, the pehead has to be held at an angle so that the fretboard is parallel to the bandsaw table.

Obviously another jig is required!

One of the few things that is not very clear in Mr. Siminoff’s book is just how to make this jig. Yes, he mentions it and shows a picture of his jig with a peghead clamped to it, but the picture doesn’t show much and he chooses not to go into detail about its design. So once again I turned to the folks at the Mandolin Cafe and was able to get several suggestions and pictures of the jigs that some of those guys use. From that, not only did I find that this can be a VERY simple jig but I was able to use one of the pictures as my guide and got-‘er-done.



All it is, is a simple wedge with a notch on each side to allow for a clamp. The corners are rounded off a bit to keep it from getting in the way while cutting.

Here I am actually in the process of cutting the peghead.




These show how I used a 2” spring clamp to hold the peghead to the jig and the clearances I have all the way around. The last photo shows how the fret board is held parallel to the top of the workbench.



In these pictures you can get a better look at the peghead itself now that it is cut. You should be able to see that the cut lines are not perpendicular to the peghead but are to the fretboard.

And this photo shows the back of the peghead after I sanded it down to make the peghead and veneer blend into the neck.

Finally, I finished the week by practicing carving a scroll on the second soundboard.

I think it looks pretty good.

Next week, if my new wood arrives, I will start again on the soundboard, but in the mean time I intend to get started bending some wood and building my new sides.