Thursday, March 14, 2019

Day 183: Jack Blanks the Traditional Way

Well, hello there! It's been a while since we last spoke. As you may recall, in my last post about jack blanks, I was executing on a hair-brained scheme to cut them on the CNC. Unfortunately, that's just not the way to go with these complex, little fellas. Sometimes, returning to first principles is the best way to go. Okay, using table and band saws is not exactly doing it like the Old Guys, but you know what I mean.

Since we last met up, I've gotten rid of some stuff and acquired some stuff. Before updating you on instrument progress, I thought I'd give a quick introduction to a few of the changes that have taken place at Tortuga Early Instruments Worldwide Headquarters over the last six or so months. First, I upgraded the CNC bed. While I won't be using it for much of this instrument, I will be cutting jack tongues with it later this month. The new CNC bed is composed of four aluminum (aluminium for my friends in the UK) t-track plates that will make it easier to clamp materials for cutting and carving.


Next, I purchased a Craftsman 6 1/8" jointer with a nice, long bed from Cool Craigslist Guy. The price was right because he had let it fall into a state of disrepair. He had lost the safety button for the power switch, cut the ground prong off the power plug, had the outfeed bed so out of level it sniped about 1/4" on the end of every cut, the adjustment wheels were hanging on by a thread and, as you can see below, he let it rust terribly. I can only imagine: "This thing is a piece of crap. I'm going to put it on Craigslist tomorrow and get it the hell out of my garage for good." His loss, my gain.


I broke out the WD-40 and a Scotch-Brite pad and went to town.


The rust practically melted off, resulting in this:


I know, I'm committed to hand tools and have owned four previous jointers, but it was time, especially with the MIDI keyboard project coming to fruition.

In the interest of keeping things on the straight and narrow, I also recently purchased a shiny new DeWalt 735 planer.


The thing is absolutely amazing (too many nifty features to mention here) and I now feel spoiled. Don't worry...I'll get over it.

Okay, back to the instrument. Once I had completed the design of the MIDI keyboard, I could confidently, and without distraction, jump back onto making the jacks. After an abortive attempt or five with the CNC, I decided to just cut them on the table saw and use a couple of jigs Owen Daly was kind enough to loan me. The first step in this process was to cut some 1" beech down to a more reasonable thickness (closer to 1/2").



I resawed the board and did a finishing pass or two on the new planer. The result? Material that was as smooth as glass and ready for the table saw.


Once I got the little pieces squared up, I went to town.



One pile became two piles in short order.



Though I need 104 jacks, I cut 120 blanks to accommodate the inevitable screwups I will introduce into the process.


The next step will be to cut the tongue slots and drill some minute (.4-.6mm) holes in the things using Owen's jigs and some astonishingly small PCB drill bits I acquired for the MIDI keyboard project. It's good to be back in the shop doing what I love: building a harpsichord. I can't wait to share my progress with you tomorrow.

Until then...


Tuesday, November 6, 2018

Project Update: Keyboards and Stuff

You're probably wondering why I've not posted anything here in several fortnights. Well, I'm working on creating a MIDI keyboard using some of the same principles I've described here. The keys will be weighted, capped in African blackwood and bone or, more likely, casein, and have a bit of a tracker action feel to them. I'm not going to divulge too much more here. Suffice it to say the design and coding work is coming to an end and I can jump back onto jack production for the instrument very soon.




Thanks for hanging in there with me. Until next time...

Monday, September 24, 2018

Day 182: Jack Blank Heaven

Yes, I'm back. I've been out for a while ascending the steep CNC learning incline. Well, it's actually not that steep, I've just had a lot going on lately that has pulled me from the project. Same news, different day. This is why it's taking me 4x longer to complete the instrument, but I digress.

The focus lately has been on making my own jacks. I'm know, this means I'm a bit touched, yet I must try. Besides, it will, as Owen Daly has said, give me specific insights into not only the jack making process, but the jacks themselves that I otherwise would not have. Now, the difference with me is that I choose to make the blanks on the CNC machine, rather than cut them with table and/or band saws.

What is a CNC machine? CNC stands for Computer Numerical Control. When I design a three-dimensional part using software (Autodesk Fusion 360 for me), I also define the "toolpaths" that guide the cutting tools, or end mills (really just high quality router bits), through the cuts. Understanding how to think in terms of negative space is key here. When using a CNC, it's a subtractive process and your design must be created in ways that are amenable to clearing material with, essentially, a router bit. The ultimate toolpath output consists of lines of numerical data (gcode) that are fed to the machine using driver software (in my case, Universal GCode Sender).

Below is a photo of the machine, including the stand I made from Craigslist-procured pallet wood, and a bit holder I made using it.


Then, there's the cutting workflow to consider. How will I make the cuts? Will they be rough or finish cuts? How much of the jack can I make with the thing? What should I define for the material dimensions (considering the unique characteristics of the cutter and dust collection boot), etc. It turns out, at least for me, the CNC generally offers an 80/20 production proposition - I can cut about 80% of a part, leaving 20% for finish handwork.

Whenever creating a new part for cutting on the CNC, I always run a prototype set first. The one in the photo below is of poplar and the lengths of the jacks are excessive, but I didn't care since I would be throwing them into the scrap bin for Crazy Chicken Lady, anyway.


I'm cutting the final blanks from a 4mm thick sheet of beech and then also cutting the tongues from a 5mm sheet of beech. Again, the orientation of the material and parts are the keys to success here. In this case, I'm cutting on the "face" of the jacks and the "side" of the tongues. Because the sheets are so thin, I installed inserts into the wasteboard of the CNC so I could use flat headed screws to hold down the material. This virtually negates the chances of hitting a clamp while cutting.



As you can see, the hold down screws are well out of the way. Once I was happy with this alteration, I charged ahead with cutting 40 jacks from beech.



As you can see, a little handwork is in order to get the jacks into shape to accept tongues. I'll sand them down and the cut the tongue bevels into them using a small, thin Japanese saw. The bevels are at about 30 degrees and their depth of cut on the front and back are determined largely by their length (if that makes any sense at all). I will be putting 5.5mm and 3mm tick marks on the front and back, cutting them, and then clearing the bevel material with a 3mm (1/8") wide chisel. Like I said, an 80/20 proposition.

Interestingly, the tongues require much less handwork after cutting.



Because I'm using a 5mm thick piece of beech and cutting them from the side, this will help them fit snugly into the space cut for the jack tongues so I can drill accurate fastening holes using a jig loaned to me by Owen. Then, I'll sand them down a bit so they swing freely in their respective slots. More to come on this exacting process.

On a tangentially related note, I did manage to pick up a Triquetra-CNC "touch probe" for the CNC. When dealing with small tolerances like those required by jack and tongue cutting, it's necessary to get the bit as close to the true top of the material as possible. A touch probe does the trick by plugging into the CNC motherboard and calling a probe function of the software I use to run the machine. This gives me complete accuracy on the X, Y, and Z planes so the cuts are flawless. It's arguably the best $70 I've ever spent.


Until next time...

Saturday, July 28, 2018

Day 181: Soundboard Down

Before I could get the soundboard glued down, I had a couple of preparatory hoops I needed to jump through. First, Mr. Miller in his eBook Most Excellent describes how the four foot hitchpin rail (on the reverse side of the soundboard - this would make the top the obverse, but I digress) needs to bump up pretty snugly against the upper belly rail at the front of the instrument. After testing, I observed that it was off by about 1/2", so I cut up one of my gluing cauls (these lay on top of whatever you're gluing to provide protection for the wood under the clamp/go bar and to spread out the pressure laterally) and taped it onto the rail and tested for fit. It was pretty close, so I glued it up.


Close, but no cigar; it was still off by about 1/32". After having gone through the previous glued linen exercise with the cutoff bar and rib scallops, I realized a folded over piece of glued linen would just about cover the final space needed.


This thin addition made the fit, in a word, perfect.

The second step was to prepare the cauls and go bars. As I said above, cauls are small pieces of wood designed to protect the wood being glued up, as well as spread the clamping pressure horizontally. In this case, I'm using former go bars of ash that I had cut too thick. I also cut small divets into them with the band saw to more securely hold the go bars - probably not necessary, but helps me sleep at night.

What's a go bar, you ask? The go bar clamping system has been around for thousands of years. I suspect the Egyptians were using it. I've seen some nice draw-bore pegs in Egyptian chairs, so why not, right? Frankly, it was probably used long before that. The system is simple; it requires two fixed surfaces and a flexible bar to bend between the two. Here, I use the assembly table, a "go bar deck" mounted to the ceiling, and oak and maple bars. You want the bars to be thin, yet not too thin with a sturdy enough constitution to not break under pressure. Softer woods are not the preferred choice.


Once everything was sliced and diced to my exacting standards (good enough is good enough), I quickly ran glue around the liners and put the soundboard under go bar pressure. My secondary goal was to not glue the cauls to the soundboard - squeeze out has a way of doing that.



The next day, I pulled the bars and cauls and, voila!, a secure soundboard was in evidence. The nicest part of this is that I can now put the instrument on its spine and the soundboard doesn't fall out, a delightful consequence indeed.


Until next time...

Monday, July 23, 2018

Day 180: Putting the Soundboard in Reverse

Once I had the ribs cut and beveled into shape, it was time to redirect my attention to finishing up the bridges. A step I had not completed was cutting a final 10-degree-ish bevel into them. The result would be a fine ridge on their tops across which the strings will eventually cross on the way to their final termination points (i.e., hitchpins). But first, I needed to plug all of the placement holes in the 8' bridge with...yep, that's right...toothpicks.



Once I had all of the toothpicks placed and cut off, I scraped down the bridge and started beveling with a block plane. I had feared this step for months, yet it turned out to be easy work. I was done in no time, except for the hook - please do not tell anyone I used a Dremel tool to smooth out the bevel there. One interesting thing to note is how the toothpick at the end of the hook had entered a pitch pocket unbeknownst to me. It was hidden until I beveled it down. I decided to keep it because it's not hurting anything and how many harpsichords have a hook like that, right?


In the end, both bridges looked pretty great.


Once the beveling was done, it was time to get the bracing glued to the reverse side of the soundboard - you know, the side opposite of the top. But first, there was another step recommended by Owen Daly that made perfect sense to me: round the bottoms of the ribs and cutoff bar a bit so that clamping them on the ends will pull down the middle and create a slight bow in the top (a good thing). I clamped the No. 62 low-angle plane upside down in the bench and went to work.


Curving the ends was a breeze. I then decided that I would glue up the 4' hitchpin rail before proceeding further with the ribs and cutoff bar, so off I went.


While the rail glue was drying, I lined out the placement of the cutoff bar and ribs using a marking tool. The next day, I glued up the ribs, waiting to glue the cutoff bar down until I had scalloped the ends of the ribs.




Then, on went the cutoff bar and its scalloping.



I keep my chisels razor-sharp, so everything went without a hitch. Owen also recommended I throw some linen soaked in animal glue onto the scallops as an extra measure. And also the Old Guys did this, so why not?


It's been in the 90s here and gluing with animal glues is always more easily accomplished in higher heat, so it's been something of a pleasure to work with the glue and get these final soundboard steps completed. The next step is to "close up the box" and get this thing headed toward completion. So far, things are looking pretty good (and, yeah, that's me in the last photo below).



Until next time...

Monday, July 9, 2018

Day 179: Making Some Delicious Ribs

Once the bridges were glued down and the rose hole cut, I could turn my attention to the back side of the soundboard; it requires five pieces:

1 - Cutoff bar
3 - Ribs of various sizes
1 - 4' hitchpin rail

The cutoff bar and ribs provide stabilization of the soundboard. Because I have a bit of a past in the guitar lutherie world, I just couldn't bring myself to make this bracing out of poplar and, following Owen Daly's recommendation, I procured a nice piece of CVG (close vertical grain) fir from Crosscut Hardwoods (paid $1 per pound) and cut all of the pieces with the quarter-sawn grain running down the sides.

As you probably know, I divested myself of my electric jointer a few months ago, choosing to rely instead on using a shooting board and the Veritas jointer plane to straigten board edges. In this case, I chose to create an index (flat) side using the table saw.


I do this by screwing a straight board to the plank I want to straighten and running an edge on the table saw. Of course, I posted about this on the Facebook project page and in the Woodworking Tips group where I received nearly no end of grief, especially with regard to my comment, which said, "We don't need no stinkin' jointer!" My favorite comment was the mansplainer who told me how ignorant I am for completely disregarding jointers and "everything they can do." Oh, boy.

Regardless of the interesting interactions, I was able to create the short edges and ran the board through the planer to complete its flattening. I'm not averse to using electric tools, I just don't have room for too many of them in my miniscule workspace. Someday, I'll have a larger shop and can tool back up accordingly. The results were great, so I charged forward.


I chose to cut the cutoff bar and ribs to dimension and then spokeshave them down by hand. Why did I do this? Mostly for safety reasons and because I just love doing handwork whenever possible/necessary.


No, the beer is not optional.


The bars are angled from top to bottom, just like the bracing on a guitar top and back. Now, I need to angle a few of the ends and get them glued to the soundboard. Once they're down, I'll get the ends scooped out (more to come on this) to create curved bevels.

On a tangential note, the days are beginning to heat up, which is actually a good thing for gluing when using animal protein glues that remain soluble longer at higher temperatures. This is the opposite of plastic glues such as Titebond, which like cooler temps in order to set up properly. So, while I usually take maintenance breaks during July and August, this year, I'll be gluing the bracing to the soundboard and getting the box closed up in the heat of Summer.

Until next time...

Tuesday, July 3, 2018

Day 178: Throwing Money Down a Soundhole

I've spent a pretty good chunk of change building out the shop, acquiring (the right) tools, and learning lessons far and wide. One of the best purchases I've made is the Shapeoko 3 XXL CNC machine. While it's largely a hobbyist's model, I love the darned thing. It fits perfectly in the shop and doesn't care which software I use to generate gcode to make it run. I use Autodesk Fusion 360 (for CAD/CAM) and two packages that came with the machine, Carbide Create and Carbide Motion, to also make designs and run the machine.

The worst thing about having a tool like a CNC machine is that it's a lot like a hammer - once you have a good one, everything starts looking like a nail. Fortunately, a CNC is not a one-stop answer for everything. In fact, it's quite limited in what it can for for me as I complete the instrument. Of course, as I learn more, that will change, but, for now, it helps me muddle through tasks that would otherwise be quite difficult to accomplish. Case in point: Cutting the rose hole into the soundboard.

I considered several ways to accomplish this. I thought about a hole saw, but had visions of the soundboard ripping to shreads under its marginally sharp teeth. Then, I thought I'd use the CNC and tried cutting the hole with an upcut router bit. A bit is defined partially by which way its spirals wrap around the bit when you hold it up by the end that is inserted into the router. If the spirals wrap to the right, it's an upcut bit; if they wrap to the left, it's a downcut bit. Some bits even have a combination of both.

An upcut bit drives the shavings and cut, as you would think, up toward the top of the cut. This is best when you want the bottom edge of the cut to be clean because this will leave a fuzzy top cut. When I tested an upcut bit, it left a fuzzy edge around the top circumference of the test material that was simply not acceptable. So, I headed to Lowe's and could only find a Dremel downcut bit, which didn't work too very well at all - it left steps in the cut, which is never a good thing. Eventually, I ordered a 1/4" downcut bit off of eBay and sat back to await its arrival.

In the meantime, Owen Daly recommended I visit him to observe how he cuts his soundholes using a circle cutter that fits into the drill press. I then remembered I had purchased one years ago and dug it out only to discover it was from that Harbor place and, basically, was a piece of junk. The test cut photos below attest to this.



The second one actually burned the wood. While I enjoy the scent of mahogany smoke as much as the next guy, it was not that pleasant this time around. I did a little research and realized I needed a better cutter, but, as with nearly every step of this project, life intruded and I was pulled away on other matters.

Until the downcut bit I ordered arrived. Then, the fun began.

The first thing I did was to run several test cuts on some cherry. Because the soundboard is roughly 3mm thick (less in some places), I set the cut pass depth at .5mm (which would require 6 passes based on the 3mm thickness of the soundboard) and let her rip.


I was quite pleased with the quality of the cut - no fuzz whatsoever - so I set the soundboard up on the CNC, held my breath, and went for it.



The result was a perfectly cut hole with a diameter of 69mm.



I shared a photo of the cut with a friend who owns a large CNC and he said, "That's one expensive circle." My reply: "Yeah, I just threw $1500 down a soundhole." Rest assured, I'll keep at it so I can amortize the cost of the machine into other cuts. Besides, it's really kinda fun.

Until next time...