Fitting the Nut

Sunday, July 26, 2009

Not having parts and then having to make yet another unanticipated business trip have really slowed down progress this week, but I have been able to get a little bit done.

As you might recall, one of the last things I did last week was to seal my test soundboard with a mildly diluted hide glue formula. After it dried for a couple days, I spent about two hours hand-sanding it off to what looks like bare wood. It is my understanding that the goal here is to “clog” the otherwise open pores of the wood with the hide glue to prevent the stain from soaking in too much without inhibiting the stain from getting to the majority of the wood fibers. From what I have read of other people’s attempts at this, its almost impossible to sand it off too much. So, armed with my trusty 80 grit paper followed by some 120 and then 220 grit paper, I sanded off the dry hide-glue layer. Here is what it looks like.

One of the interesting things I found while sanding the glue off was that this is a really good opportunity to find and correct many of the imperfections in the contour of the top. The hide-glue dries just a little bit darker than the color of the raw spruce so each dip and valley, regardless of how shallow, shows up. I was quite surprised at the number of irregularities I found. I believe using this will really help the appearance of the finished mandolin.

With the fretboard now in place, it was time to install the nut. But before I could do that, I realized I needed a padded block to go under the neck while the mandolin is laying on its back to prevent hold the peghead off of the workbench. For this I picked a scrap piece of wood that measured about 1-1/2” x 3” x 4”, cut a shallow wedge in the center of the 4” long face, and glued a piece of soft leather to it. Here is how it looks.

NOW it was time to install the nut.

I started by measuring the width of my slot with my digital calipers. I measured both edges to make sure they were about the same, and much to my surprise, they were within .001” of each other.


I then measured my nut blank (bone - ordered and received way back).

Since the difference between the two was almost half the thickness of the nut blank, I decided to use my drill-press-drum-sander to get it roughly to size. (I used a piece of scrap would to verify the thickness before committing to the nut itself).

Once run through the drum sander, I measured again.

With less than 1/10th of an inch remaining to trim, I stopped there and finished sizing by hand.


I already new that the height of the blank would need to be trimmed but before I could do that, I needed to be able to mark the correct fret height on the nut and this could most easily be done once the nut was correctly sized to fit the slot.

Now to find a way to mark it.

I read somewhere that somebody had taken a wooden pencil, cut it down the center to create a “half” pencil and used this to mark the fret height - so that is what I did. Rather than try to cut the pencil, though, I used my drum sander again to sand away the unwanted half of the pencil.

Using my drum sander once again, I removed all but about 0.30 inches of material above the fret line and then hand-contoured it to shape before gluing it into the slot with Titebond. Here is how it looks now.


As you can see on the top photo above (if you look really hard, anyway) you can see I have marked where the notches for my strings will.

My brother-in-law read my last post where I wrote about buying and using feeler gauges for saws and offered up an old set that he had (and no longer used) for creating my “saws”. Not being one to look a gift horse in the mouth, I accepted and found that this set has a much wider selection of thicknesses.

And, last but not least, the remainder of my parts finally arrived late this week. Now that they are here and assuming I get to stay home a bit more this week, I should be able to get the rest of my binding on and try my hand at staining. I am really looking forward to the staining - if I am lucky, I may get to even try it on the mandolin, not just the test piece.

Binding the Soundboard and Installing the Fretboard

Sunday, July 12, 2009

Progress this week was hampered a little bit by a couple things - a short business trip that kept me away for a couple of nights and my most recent order from Stew-Mac is being held with one item on back order. Consequently, about all I was able to accomplish was gluing on some of the binding, attaching the fretboard extension, and gluing on the fretboard.

I finished up last weekend by hand carving the remainder of the grooves for the bindings and then, this week, I shaped and glued the binding around most of the soundboard. Rather than attempting to shape this binding with the heat gun like I did for the fretboard, this time I chose to use a similar to the one I now use to heat my hide glue - hot water. Since the temperature of water does not have to reach boiling to soften the binding, the likelihood of burning oneself and the binding is pretty slim and it is also easier to fine-tune the shape since all you have to do is dip the specific section into the water. I will probably drop the heat gun method now that I know how easy water is to use.

This picture shows the binding being glued on to the outer ring of the scroll. I have used painters tape to hold it and have chosen to glue the scroll first while leaving the body free. This allowed me to focus all my attention on getting the scroll binding tight without having to worry about the body, too. I came back later, after the scroll binding was dry, to glue the remainder of the body binding on.

Next, having run out of binding to glue (I did not order enough to do both the front, back, peghead, and fretboard and the rest is coming in the back-order I mentioned before) I chose to move on to installing the fretboard extension. A couple of weeks ago while waiting for my inlay glue to dry, I spent time making the fretboard extension fit with the soundboard. This meant a good deal of scraping and sanding on the soundboard and the extension itself, but eventually I got the two to fit pretty well. So now, having installed a short strip of binding in between for cosmetics, it was time for gluing

To securely hold the extension while the glue dried, I drilled a hole through it and into the head-block. The screw, being on an angle as it is, creates force both down and back toward the neck. For glue, I used Tite-bond on the base and weld-on cement in the joint that mates with the binding.

After allowing the glue to dry over night, it was time to level the extension with the neck. Checking regularly with a straight edge, I sanded the extension until the two were level.


Finally, I glued the fretboard on. Once again, because it is a relatively normal practice to have to remove or replace a fretboard, I used hot hide-glue for this job. I left approximately a 1/8” gap between the fretboard and the peghead for the nut and I hope to be fine tuning this gap to size and cutting the nut to fit this week.

Installing the Back

Monday, June 29, 2009

The facility where I work is shut down for the July 4th week and my poor wife does not get that luxury, so I get to spend a whole lot of quality time working on my mandolin.

Today I got to glue the kerf lining and the back on.

Similar to the way I aligned the soundboard when I attached it to the sides, I started by installing three alignment pins. These pins, located in the head-block, tail-block and lower point block, are actually just small nails that have been cut off and put in backward so that the point goes into the back when installed.

First I drilled the holes. The bit for this is just big enough to allow the nail to be pushed in by hand - it doesn’t need to be really tight.

Then I inserted the nail (point first) all the way to the bottom. Using my handy linesman’s pliers, I cut the nail as close to the block as I can. Because the cutters in the pliers are inset from the face closest to the wood, I know that the remaining nail will be a little long - just like I want it.

Then I pull the nail out of the hole, flip it over so that the point is up, and tap it securely to the bottom. Now, when I get the back exactly aligned with the sides, all I have to do is squeeze the two together. This will force the nail points into the back wood and give me repeatable locating holes. The nails, of course, are now permanent parts of the mandolin.

Next, just as I did for the soundboard again, I glued in my kerf lining and then once it dried, I sanded it flush with the sides.

Here is the last shot (hopefully) anyone will ever have of the inside of this soundboard.

At that point, the only thing remaining before gluing on the back is to give this sign the inside of the back so that one day, when I am dead and famous, the proud owner of #1 can prove who built it.

And now, because the internet will live forever, there is documented proof of just what it reads.

Ok. Enough of that. Back to the building thing.

As I pointed out earlier in my various attempts to use hot hide-glue, it sets-up really fast and anything that can be done to get clamps in place quickly is valuable. So in preparation for gluing the back on, I started by cleaning everything off of my workbench, dry-clamping the back to the body, and then laying out all my Bessie clamps and cello clamps so they are ready to go. Here is how it looked while I was heating the hide-glue (far left of the photo).

From start (applying the glue around the perimeter of the body) to finish (tightening the last cello clamp) took only 5 minutes. Fortunately, during my dry-clamping, I found that I could strategically apply four Bessie clamps and five cello clamps to close all the major gaps and then come back to add the remaining cello clamps. I believe I had these first nine clamps on in just over 1 minute. Here is how it looks while drying.



I’m going to let this dry over-night and then, maybe as early as tomorrow, I will use my belt sander to sand down the edges of both the soundboard and back to match the sides (both are oversized now) and get started installing binding around the body and peghead.

Soundboard Repair Complete

Friday, April 24, 2009.

Well, today I got home from work excited to check out my repair joint and pat myself on the back for a job well done. I had, after all, found a way to repair the glue-joint on a "finished" arch-top mandolin. So, after dinner, I took to the task of removing my spring clips and removing my repair blocks.


Looking pretty good. Dried glue beaded up on both the top and bottom of the joint - no problem.

An after only about 3 minutes of block removal - pretty easy.

Then I started scraping and sanding.

And reality hit home.

This was not only the dried glue beaded up on the joint, but the joint itself standing out like a sore thumb. And gaps - not huge ones, not ones that go all the way through - lots of little gaps.


Clearly I can’t use this on a real mandolin - not with a big-ole line down the middle. So I guess it now becomes a wall hanging or expensive kindling. I can’t even use it in the how-a-mandolin-is-built display I want to build someday.

Oh well. I got my new top and side wood earlier this week so I plan to start remaking those parts again this weekend.

So what lessons have I learned from all this, you might ask?

First - when you think you are ready to glue two pieces of wood together, check again that they going where they should and, then, check again.

Second - once you have glued your tone bar in the "wrong" location - leave it.

Third - when you remove that wrongly located tone bar, don't try to salvage it. Carve it out. Destroy it.

Fourth - when you do decide to soak that tone bar free, order new parts. You'll need them.

And, of course (as we all already know), don’t eat the yellow snow.

Later.

Gluing the Soundboard - Again

Thursday, April 23, 2009.

As I had hoped I got all the repair blocks glued on last night.


And this evening when I got home from work, I started by preparing the mating edges of the soundboard halve for gluing. For this prep I decided that I needed to sand the edges smooth. To do that, I needed to sand the entire edge at the same time and that required as flat of a surface for the sandpaper as I could find. Not having anything better, I took the pane of glass that I originally purchase for use when sharpening my planer blades. I took off the sandpaper pieces that were already taped on and then taped on a full sheet of 350 grit sand paper. I then took the first of the two soundboard halves and, holding it by the repair blocks, began to sand it gently length-wise.

After sanding for a few moments, this was the pattern left on the sandpaper showing where the contact was.

Clearly, my joint was not as flat as I needed. Once I was happy with it, I moved to the base side. Here is its contact pattern.

Even worse!

Once I had sanded both halves to where I was satisfied that they were as square as they would get, I switch over to 600 grit paper to finish. Holding the two halves together up to a light showed no gap. Woohoo!

The next step, of coarse, was to dry clamp the two halves together as practice and to verify that everything would work out once glue is applied. Good thing I did. As it turns out the spring clips are way too strong for this application as they come out of the box. As it happens, two of the repair blocks broke of under the pressure. So, to correct this problem, I chose to “spring” the clips to weaken them. That was a simple process that I was able to do by hand.

Once sprung, the clamps offered a small but sufficient force and I was ready to glue.



I am pretty pleased with the way this all seems to be working out but it is difficult to be sure since the glue squeezed out both the top and bottom of the crack. Tomorrow will tell the tale.

Getting Ready to Repair the Soundboard

Tuesday, April 21, 2009.

So I have started with my repair of the soundboard. To begin with, I thought I would make sure to document what it looked like before the repair:

You can just see the faint crack going most of the way up the center. I would have included a picture of the outside, but there was really nothing to see in that photo - the crack was almost impossible to see with the naked eye and did not show up at all on the picture.

And here are pictures right after I managed to get it in half. To do this, I had to purchase a heat gun rather than using a hair dryer as I had planned (my wife's hair dryer puts out almost no heat at all!).


One note of caution for anyone like me who has never used one before - I purchased one of those heat guns that are sold in the wallpaper section of Lowe's - those things put out some serious heat. I actually scorched the wood a tiny bit without even trying.

Here are the repair blocks I made to glue on the inside and outside of each half. I made about 40 of them. You will notice I made a small mark on some of them - this was a visual reference I used to let me quickly find the side I sanded in preparation for gluing.


Me sanding one of the blocks. I am using 600 grit paper for this. I am hoping that is fine enough for this repair step. I also sanded the mating areas on the soundboard with 600 grit paper and wiped both down with a clean, dry rag before gluing.

And, finally, here I have clamped the repair blocks to the top of each side using hide glue and clothespins. I am only gluing the blocks on the top tonight because I was worried that if I tried to clamp on the bottom as well, something was going to get knocked out of position. I would rather take two nights to do this than mess it up by being in a hurry.



Now we wait till tomorrow night.