It's been quite a while since I've updated you, dear reader, on my jack production progress. In fact, it's been around six months - far too long for us to have been apart. Of course, an intervening pandemic hasn't helped matters much, but it also hasn't slowed down the jack making progress, just the blog posts. Also, please note that I've changed just about every jig and process from previous posts, so the next few updates are entirely warranted.
Before launching into several posts about making Flemish style jacks for harpsichord copies, particularly those of the Ruckers family, let's revisit the need for me to make my own jacks. Frankly, it comes down to me listening to Owen Daly when he says I should at least learn to make jacks in the interest of understanding the details of not only the making process, but the jacks themselves. As with everything harpsichord, Owen is right.
The wonderful Harpsichord Project 4.1 eBook by Ernest Miller that launched me down this path specifies jacks to be purchased from Hubbard Harpsichords. I've taken so long to complete the instrument that Hubbard Harpsichords have shut their doors. But there are other options. Two notable names in the jack making world are Purdy and Austin, both of which I'm sure could supply me the sets I need to complete the instrument, yet I soldier on with the support of Owen and Paul Irvin, another master builder who lives just 10 miles south of me.
It's been a long and winding road getting to the point where I can produce jacks reliably and without too much angst. While they are small and somewhat unassuming, jacks hold many subtleties hidden from the casual observer, all of which I will cover in this and subsequent posts. So, I'm back now to share the information and education I've gleaned over the last six months, much of it born of mistakes, most of it learned from the masters.
Let's begin with the jack bodies. The jack body rests on the end of the key farthest from the player and rises as the key is fulcrumed up during play. Jacks contain a slot into which fits a "tongue" that holds the "plectrum" which plucks the string, rendering the unique harpsichord sound we've all come to know and love. First, we begin by carefully slicing the jack body blanks from Eurpoean steamed beech stock; the dimensions are 12.7mm (1.2") x 5mm (just over 3/16") x 152.4mm (6"). We only need 104, but we cut 120 just in case.
Next, we clean up the jack body blanks using a Lie-Nielsen 62 low-angle jack plane with a jig I designed and made on the CNC machine. I've been adamantly advised against using the CNC machine for any kind of instrument manufacturing, yet this is a clear case where it benefits both me and the instrument.
As you can see, the jig holds the plane and jack body nice and snug for good precision. I made it from poplar, a fairly soft wood, to protect the plane blade from overwork. When it wears down, as it most certainly will, I will simply cut another from the hundreds of board feet of poplar I have standing in the shop.
Then, 5mm tongue slots are cut into the jack bodies on the table saw using a shop-made jig and custom blade with 5mm wide, flat carbide teeth.
The jack blank that lies perpendicular to the jack body under the jig in the photo above is used to keep the jack body flat and stable as it is pushed through the blade. Eventually, we end up with a box o' jack bodies with tongue slots.
The next step is to drill the holes for the PEEK filament spring. This spring is light and keeps the tongue in place, even as it slides around the string on retraction (i.e., fulcruming down after the pluck). For this operation, I designed and built a jig that uses an adjustable vise that clamps down a jack body holder. On the other side, I purchased two 3D printer linear rails/bearings on which I mounted a Dremel tool with an extender to hole a .6mm drill bit typically used to drill printed circuit board holes.
The drill bit enters the jack body at a 15-degree angle, resulting in a divot on the back side (really the eventual front side of the jack) that acts as a channel for the PEEK filament. We then clean them further using a jeweler's file. In the photo below, my secret jack-making weapon, Conner McClure, is doing this work.
Next, we will examine the manufacturing process for tongues, something that sounds a lot more fun than it actually is. Because the tongues are a somewhat laborious and intricate process, I'll save their details for the next few posts and hope to see you there.
Until next time...
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