After getting the body together, the next step in the process was to trim the overhanging material from the back and top to be flush with the top and then to rout the channels for the binding and purfling. The binding will be placed along the seams of both the back and top where they join the sides of the guitar in order to hide the end grain that would otherwise show. The purfling is a strip that is placed adjacent to the binding all along the perimeter of the top of the guitar for decorative purposes. In my case, the binding is Ivoroid and the purfling is a black and white Herringbone pattern.
I have to say that this was the most nerve-racking part of the build so far. After all of the work that has gone into building the box up to this point, the idea of taking a router to it was a bit daunting! As I will explain, this operation had the added complication of dealing with the arch of the top and back while routing to maintain the router in perfect position so that the channels were at the appropriate depth and width to receive the binding and purfling.
I didn’t take any pictures of the flush trimming operation, but I will walk through the binding/purfling operation because the same procedure and jig were used to first trim the top and back flush with the sides. Of course, this was done with a flush-trimming bit in the router.
What you realize very quickly when examining into how to perform this operation is that because of the arches in the top (1/5 degrees) and especially the back (5 degrees), the router base – even on a small laminate trimmer – will not allow the cutter to remain parallel with the sides while moving around the guitar. Similarly, because of the varying contour of the back and top the cutter may also have a tendency to move up and down during the cut leaving you with channels that vary in size.
There are varying ways to deal with the challenges posed by this situation. Everything from scoring and cutting the channels by hand with a specialized tool to creating an elaborate telescoping and/or vertically movable fixture for the router to mount on while moving around the guitar body. In the end, I opted for a compromise and created a simple jig for my Bosch Colt router. In the pictures you can see the jig clamped into position on the router base. The main section is designed to align with the bearing of a rabateing bit that cuts the correct depth channel. If If this section is held vertical and in contact with the side of the guitar while routing the channel will have a uniform depth. To help with this there is a small piece double-stick taped to the router base, effectively moving the base contact point very close to the edge of the guitar where the arch will not affect the width of the channel being routed. The last picture shows the router in position to rout the channel for the binding.
The operation started with trimming the back and top to be flush with the sides. There are some other issues to deal with here concerning grain direction. Because of the rotation of the bit and moving with and against the grain there was a danger of tearing out pieces of the back and top during the routing operation. As a result, I first made a series of clockwise climb cuts in select places and then followed up with a complete pass around the guitar in the standard counter-clockwise direction. The picture shows the path of the clockwise climb cuts in red and the following counter-clockwise pass in blue.
Routing the channels for the binding was next. Even though the back had more arch to deal with, I started there thinking that if I made a mistake, any fix would be less noticeable on the back. The four climb cuts came first and then the standard cut. This was done with a bearing on the rabateing bit which cut a channel that was bout .60″ deep to match the thickness of the bindings. Things went OK on this, with a couple of bobbles of the router that will require some hand cleanup. So, then it was on to the top following an analogous procedure. Again, things went OK but some hand cleanup will be required. Next, I switched bearings on the bit, reset the cutter depth and adjusted the jig to allow routing of the purfling channel along the top – same sequence of cuts with lots of trepidation! Again, a bit of hand cleanup will be required but, the stepped channels for the top binding and purfling are now in place.
In the pictures you can see the results of the operations along with the dry fit of the binding and purfling. The jig worked well. Probably the only thing I would change the next time is to use a slightly smaller piece for the contact point so it is affected even less by the contour of the back and top. Also, I found that keeping the body stationary while routing was a challenge. It turned out that keeping the router in position was not that hard with the help of the jig but, keeping the body from moving during the operation was an issue. The next time I think I will create a fixture that clamps and raises the body into a stable position for the operation.
Tags: binding, dreadnought guitar, guitar, lutherie, purfling, router, routing
In the last post, I wrote about attaching the top to the sides. After completing that it was time to finally get the body completed and closed up.
In order to do this I first had to repeat the process of fitting the back to the sides and notching the kerfed linings to receive the back braces. I followed the same procedures as for the top described in an earlier post. The important thing here was to assure that the body length was 20″ from the neck block to the tail before cutting the notches. Even with the inside mold and the top applied, the sides still flexed a bit so, I made sure that things were aligned to the previous marks that I made on the underside of the back.
Once I had the notches cut for the back, it was time to finally remove the inside mold. I scored an X-shape into the cardboard with a sharp utility knife and pulled out the triangular pieces. This finally gave me a view of how I did on the top glue-up. I guess I did a reasonable job of estimating the amount of glue to apply because there was no squeeze-out on the inside of the guitar body!
One more thing needed to be completed before attaching the back. For reinforcement, strips of spruce were applied to the sides periodically along the perimeter of the guitar. These were simply cut to size to fit between the kerfed linings and glued. The clamping was a bit cumbersome because of the depth of the sides. As I went along on this I created some cauls with some scrap and added tape to the ends so that one clamp could apply pressure to the entire strip. The only thing I found that was problematic during this process was controlling glue squeeze-out . I tended to wait until the glue gelled and then scraped it off however, working around the clamps in a tight area was a bit tedious.
I made sure that the inside of the guitar was clean and then went about gluing and clamping the back. This operation followed much the same procedure as attaching the top. I used the same spool clamps along with a couple of Quick-grip clamps at the neck and tails blocks. In the first picture you can see the glue applied to the neck and tail blocks and the kerfed linings. The second picture shows the clamping masterpiece with the back in place waiting for the glue to dry!
I waited 24 hours for the glue to set, removed the clamps and inspected the joint all along the back. Things looked good so, there was one more operation to complete before I could move on to routing the channels for the binding and purfling. The last thing to do was to remove the little square of wood on the top that covered the neck mortice. I scored inside the edges of the neck mortice with a utility knife and then cut short saw kerfs with a flush-cut saw (just because that is the smallest saw have no hand, not because I was cutting flush with anything). I worked the end of the piece with the knife until I could snap the piece off and then cleaned things up with a sharp chisel.
As I said, routing the channels for the binding and purfling is next. That will be an interesting operation. It will require some jigging in order to do it properly. We’ll cover that in the next post. If you have any questions or comments, please either leave a comment using the comments link at the end of the post or send me an email at thecraftsmanspath@gmail.com.
With the bracing completed and the notches cut into the kerfed linings, it was time to start the work to attach the top to the sides. However, this task was not going to be able to be completed without some creative clamping.
Because the top must be clamped all along its perimeter, any normal clamping scheme would require quite a number of clamps in oder to adequately attach the top to the sides. When I previously glued the braces to both the top and back plates, I used the go-bar deck with flexible go-bars as clamps. This technique would also work for attaching the top (and the back as well) however, there are a few issues with it. First, in order to do it I would have to cut down all of the go-bars due to the hight of the sides. Second, because there is a radius along the edges of the sides, the setup would not be very stable to clamp with go-bars without something to compensate for that radius.
So, what to do? Go out and buy a bunch of light duty clamps? No – just borrow another page for the old-time luthery book and make some spool clamps. In the picture you can see the pile of these that I made. Twenty-four of them, to be exact.
The spool clamps are fairly simple to make – an 8″ carriage bolt, some 1 1/4″ dowel rod, some fender washers, wing nuts and cork. It was a bit tedious to glue the cork to the pieces of dowel – I did this in strips (after the dowel pieces were already cut) and then trimmed the cork to the edge of the dowel with scissors. Not pretty because the cork is a bit crumbly, but it works. The only other issue was drilling holes through the dowel and cork for the carriage bolts to pass through. To do this I cut a circle in piece of MDF and cut a line with the band saw into circle from the edge. This allowed me to squeeze the circle closed with a screw in order to clamp each piece of dowel while drilling the holes.
OK so, with that activity all done, before I could attach the top, I needed to cut away the side material that was overlapping the mortise in the neck block. To do this I scored inside the lines of the neck mortise with a sharp utility knife and snapped away the side material. Finally I trimmed away the rough edges of the sides with a sharp chisel until they were even with the sides of the neck mortise. The rounded bottom does not need to be perfectly true because the neck tenon does not actually contact it when assembled.
With the neck mortise clear, it was time to dry fit the top, make any final adjustments and then glue it up. The important things here were to be sure the the neck edge was 3 15/16″ from the sound hole and that the tail edge was 20″ from the neck edge. I had previously measured these locations and marked them on the underside of the top with a pencil so, I was ready.
I applied glue sparingly to the kerfed lining strip along the top edge of the sides – I did not want any squeeze out on the inside of the guitar body. The clamping started at the neck end with a couple of Quick-grip clamps and a caul. With these clamps in place, I added a few spool clamps along the upper bout on each side of the neck block. This allowed me to then apply a clamp from neck to tail to bring the tail in to the 20″ mark. From there I just clamped the tail and added spool clamps along the sides – the last two being applied after the waist clamp was removed.
Well, I never did get to that other post for Woodworkers Safety Week 2008 but, I think that if you took the time to read some of the blogs you saw enough of the menagerie of safety devices available to help keep you safe in the workshop. At some point I can do a post about some of the more unique things I have done in my shop for safety’s sake. Now, on to the matter at hand…
When we last left the Dreadnaught Guitar project, I had completed all of the bracing for the top. The next step in the project is to glue the top and the back to the sides. However, before this can be done, the kerfed linings must be notched for the braces and the braces must be trimmed to intersect with the linings appropriately.
In the picture, you can see the guitar sides (still in the waist clamp) mounted in the vice on my workbench. I clamped the top to the sides temporarily in order to mark where the top braces intersect the sides. This was important step which required some careful measuring and squaring. Even though there is an inner mold supporting the sides, there is still some play in them. When clamping the top on, I made sure that the neck block area was as square as possible to the guitar top. This is important because it will minimize adjustments to the neck when it gets attached later (I’ll need to repeat this step when I actually glue the top, as well) It was also imperative that the neck block be located at 3 15/16″ from the sound hole and that the tail block be 20″ from the neck block. Once all of this was set I clamped the top to the sides.
With the top clamped in place I marked the positions of all of the braces where they intersected the sides. I made sure to capture than angles that the braces made as they crossed the sides. After this was done, it was time to mark the braces along the sides to indicate where they would need to be trimmed to. I did this while the top was still clamped in place so that I would not have to repeat the placement again later.
Now it was time to cut the notches in the kerfed linings to receive the braces. I’ve seen this done two ways – one way is to cut all the way through the sides where the braces intersect, the other is to cut only through the kerfed linings to create a little “pocket” for the ends of the braces to be glued into. I chose the latter. It just seems to be a more refined way to do this. To do this, I used a knife along the marked lines at an angle to create a kerf on each side of each notch and then carefully removed the waste with a sharp chisel. It was important to only recess these notches down to the height of the braces (about .100″). They also had to be angled slightly to match the angle on the ends of the braces.
With the notches cut in the linings, I moved on to the top to trim the braces. Because my previous marks were made on the outside edge of the sides, I moved in toward the center of the top a distance equal to the thickness of the sides from my marked locations. I made a narrow saw kerf at that location and then removed the ends of the braces with a chisel. I also reshaped the ends of the braces to be sure that they finished at about .100″.
Next, it will be time to glue the top to the sides. However, before that can be done I need to make some special clamps to help with the process. Of course, once that is done, I will have to repeat this process for the back.
As you may already know, this week has been declared Woodworkers Safety Week 2008. This idea was the work of Marc Spagnuolo of The Wood Whisperer fame. Along with the declaration of Woodworkers Safety Week, the thought was that those of us who write, talk, or video about woodworking might focus some of our efforts during the week on the subject of safety in the workshop. The emphasis of this endeavor is, of course, to heighten every woodworker’s awareness of the need for safety in the workshop.
To do my part for Woodworkers Safety Week 2008, I thought I’d share a couple of quick stories about close calls that I have had in the workshop, the reasons for them, and what I learned from the experience. In addition to these stories, in a subsequent post I will also highlight just some of the things that I use in my shop that are focused on safety.
What you see in the picture is the sign that I have hanging in my shop. I got if from an old manufacturing operation that was closing down and I thought it would be perfect in my shop. It’s location in the shop causes me to see it every time that I enter. It may seem silly, but seeing it every day in the shop reminds me that the first thing I can do to be safe is to think clearly about what I am doing. If something that I am about to do does not feel safe, I don’t do it – plain and simple. This practice has never failed me. I will always spend extra time thinking about or setting up for an operation to make it completely safe. To me, the extra time is well worth the piece of mind I get as a result.
Having said this, I too have been through the “woodworking school of hard knocks”. When I first started out in the craft, I of course did not have much experience doing woodworking. On two separate occasions this lack of experience (and the lack of patience to try to research the write way to do something) resulted in a close call for me in the shop. One was at the table saw and the other at the router table.
The Table Saw Incident
The table saw incident occurred when I was first starting woodworking. I was using my father’s old Craftsman 7 1/4″ table saw. It had a very poor fence on it. I was attempting to rip a board but I had two things working against me: I was not using a splitter and I did not have the fence tuned to align itself parallel to the blade when it was locked down.
I started the ripping operation and the board started to become harder and harder to push. I could hear the saw straining but, I kept pushing thinking that there was only a little more to the cut and I thought that I could force it through. You can probably guess what happened – because the fence had locked down with the far end closer to the blade than the near end, and because there was no splitter to keep the board from contacting the rear of the blade, the board eventually rode up onto the rear teeth of the blade and kicked back with violent force. Luckily, I was standing in a position where it did not hit me but, the board ended up going through a paneled wall on the other side of my shop! Needless to say, I quickly shut down the saw and after I collected myself I finally did one thing right – I retraced what I had done and realized that the issue with the fence was the cause and that my forcing the cut and the lack of the splitter enabled an almost tragic result. The important lessons that I learned from this are:
- On the table saw a well tuned fence is paramount. Until I got my own saw I was diligent to check and recheck that the fence was equidistant at both the front and back of the blade before any cuts were made.
- Having a splitter on the saw could have helped this situation. Because this saw was old and the guard/splitter was long gone, I made a new insert with a wooden splitter attached until the saw was replaced.
- Forcing a cut on any power tool is the last thing you should do. From then on, if ever in a situation where a cut is binding I always shut down the tool to investigate what is causing the issue before continuing.
The Router Table Incident
The incident that I once had with the router table was not because of an issue with the equipment but, rather because of an issue with my knowledge of an operation. I was using a straight bit in the router at the router table to plow a groove.
I had already plowed a groove in my workpiece using the fence on the router table to position the groove properly. I moved the piece from right to left over the bit to do this. However, the bit I was using was 1/2″ in diameter and I needed to plow a 3/4″ grove into the piece. I was not quite sure, but this seemed simple enough…I could just move the fence in toward the bit by 1/4″ and widen the groove with another pass against the fence, I thought. I went ahead with this operation and as soon as the piece was engaged by the bit, it shot out the left side of the router table and into the wall across the shop! This happened in an instant and I hardly knew what had happened. I shut down the router and tried to understand what had gone wrong. After a bit of thought, I finally understood the problem. Because I moved the fence toward the bit and still fed the piece from right to left, as the bit rotated counter-clockwise it was widened the groove nearer the edge of the piece that was against the fence. This caused the piece to be trapped in between the bit and the fence effectively creating a climb-cut situation. The important lessons that I learned from this are:
- You need to always be aware of the rotation of the bit on the router table. All operations must feed the workpiece to be cut into the rotation of the bit – it is always worth a few extra minutes to walk through the scenario (and even draw a quick picture) to be sure that you completely understand what you are doing.
- Never ever trap a workpiece between the bit and the fence on the router table. Always consider the rotation of the bit and if the orientation requires the cut to be between the bit and the fence, then the feed direction must be reversed. In the scenario that I denoted above, I needed to actually feed the workpiece from left to right to safely make the cut.
These are the two close calls that I have had that stand out the most in my mind. They illustrate that disastrous things can happen in an instant in the workshop. I hope that reading about them will point out something for you to work more safely in your woodworking. I would also urge you to visit the other blogs in The Woodwhisperer Network to see what others are talking about during Woodworkers Safety Week 2008.
Tags: safety, Woodworkers Safety Week, woodworking safety, workshop safety
