Day 185: Jacks Yet Again

It's been a long while since I've updated you here. My apologies. Things have been hectic and I've been awaiting a new custom made table saw blade with 5 mm teeth from Snooks Saw Service in Salem, Oregon (recommended by Owen Daly, of course). Well, the monster finally arrived, so I went to work on the jack blanks I had cut a few weeks before.

Rather than run them through barehanded, I grabbed some walnut from the stash and made what I think is a nice, little jig that will keep my hands safe. I used the CNC for maximum accuracy, as well.

I'm quite happy with it, though there is some tearout that happens based on the flatness of the teeth and the lack of support as the blanks meet the blade. Some loss is unavoidable, but nothing I can't live with. As you can see, the tongue slots came off nicely.

Because I had cut the tongues on the CNC, including setting the axle holes there, I could drill the axle holes into the bodies of the jacks using a .7 mm drill bit with great precision. These bits are typically used to drill holes into printed circuit boards and work quite nicely for this purpose.

As you can also see, I made a placement jig for these, too. It works. I was able to drill 99 without breaking a single bit.

I then inserted the pins I will be using into a hole and through a tongue and...it worked!

Now, to make jigs for the PEEK spring holes and to cut spring reliefs into the backs of the tongues. Just today, I located a 9" band saw for $15 on the Facebook Marketplace for this very purpose that I'm picking up tonight. I'm sure you'll see it in action in the near future.

On a couple of tangentially related notes, I came across an amazing sale of tools and wood downtown Portland a couple of months ago. I ended up grabbing about 3 gallons of Natural Danish Oil, a Fein shop vac for the CNC, and a couple of hundred board feet of poplar.

I won't need to purchase poplar for a very long time.

I also recently added a wonderful new book to the library.

The only other two books that have had as much impact on me are Hubbard's Three Centuries and O'Brien's Ruckers book. The analyses and articles are just amazing and I can't wait to apply some of what I've learned to the instrument.

Until next time...

Day 184: More Jack Work and Other Stuff

As you can imagine from past posts, the jack work continues, as do the diversions. Lately, I've been concentrating on making the jack tongues using the CNC. After laying them out in Autodesk Fusion 360, I first drilled .7 mm holes for the axles using a tiny, little bit I purchased for printed circuit board work.

Completing these cuts required a tool change to a 1/8" (3.2mm) bit so I could shape the bodies.

When cutting with a CNC, you always want to leave "tabs" between the items you're cutting so the spinning router doesn't send material flying across the room if the endmill touches it. In this case, I didn't cut quite all the way through the material, so I had to clear some of it using a razor knife.

It all worked remarkably well. The only thing I'm worried about is how to line up the axle holes with the mounting holes in the jack bodies at a later date. Owen Daly's voice is running on a loop in the back of my mind admonishing me to drill the holes with the tongue wedged into the jack tongue slot. I guess we'll see if I can pull it off.

As a means of diversion, I recently made a bookcase (a honeydo model). I only post it to partly explain the holdup in jack production. Because the Tennessee red cedar was in a pretty raw state when I purchased it from Crosscut Hardwoods in Portland, it took days longer than it should have to complete the project because I basically had to mill my own lumber to dimension.

It's a nice, little bookcase, but I'd really rather make instruments.

In a few tangentially related shop matters, I recently replaced the old radial drill press with a newer, larger, version. I must admit it was hard letting the old fella go, but I persisted.

Old Fella

New Fella

After wrestling the Tennessee red through the table saw and having visions of a horrible mishap, I replaced the crappy Grizzly aluminum table saw fence with a Delta T3. It has made all the difference and the blade now goes through wood like a hot knife through butter.

I also picked up a dial gauge to use for setting jointer blades, checking CNC wasteboards for flatness, etc. It was time I stepped up the level of accuracy at Tortuga Early Instruments Worldwide Headquarters.

Finally, as I was working on the Tennesse red, I ran across this fellow:

He surprised the heck out of me, but I went with it and he ended up part of the bookcase. Feel free to help me name him - I'm thinking something like Tennessee Red would work.

Until next time...

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 as I complete this mini-project.

Until next time...

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...

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...

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...