Buffet English Horn Day 17 - 3/1/14

First day of padding! Though not before taking care of a few other things first.

Although I had already faced the upper joint tone holes, I decided to go back and check everything again with a discriminating eye. And it's a good thing I did, because a lot of them still had chips or uneven rims, and needed more attention. The order of operations I ended up using that gave me the results you see below is this:
1) Dip the head of a pin in medium-thin superglue, then run a bead around the rim of the tone hole. Allow it to set a few minutes
2) Dress the tone hole's outside taper with my fancy new facers covered with 220 grit sandpaper
3) Establish a flat surface on the top of the tone hole with the flat side of the facer and 600 grit sandpaper (the 600 grit loads up quickly so it has to be replaced frequently)
4) Once a smooth, flat surface is established (ideally not too wide), chamfer the inside of the tone hole with a pad seat reamer (pictured, available from Ferree's Tools)
5) Check everything under magnification. Sometimes the pad seat reamer catches on the tone hole rim and chips it. Simply fill any chips with glue and repeat above steps.
6) Continue checking obsessively until your eyes hurt
The result is a smooth, even, defect-free rim like you see below.

With the tone holes faced, I took a detour to a small project on the upper joint - wrapping the upper tenon rail in silk. Wooden tenons - especially middle joint tenons - tend to be come wobbly over time. A lot of players seem to think that this can be remedied by replacing the tenon cork, but the tenon cork really only does two things. It provides friction to prevent the joints from falling apart (longitudinal movement), and it acts as a gasket to create an airtight seal between the joints. A tenon cork can't, however, eliminate wobble (lateral movement). The middle tenon on a woodwind instrument is usually very short compared to the length of the upper and lower joints, so those joints exert a huge amount of leverage on that little tenon. Cork is just too soft to be able to withstand those stresses. The rails, however, are strong enough to hold up against that lateral force and prevent wobbling. Rails can either be wood (or plastic, if that's what the instrument is made of) or they can be shrouded with a metal sleeve, in which case the socket will have a matching metal liner.

Metal rails have a two-fold advantage. First, they don't expand or contract with changes in humidity and temperature, so if an instrument has metal rails and a metal-lined socket the tolerances between them can be very close to ensure a snug fit. Wood rails and sockets swell and contract a lot more, so they can't be fit as closely lest they become stuck. The second benefit of metal rails is that they don't wear as much as wood. Even a wood as tough as grenadilla will eventually wear down under the lateral stresses exerted on the middle tenon. That's why older clarinets and oboes almost always have a wobbly middle tenon, and why this english horn did, too. 

Whoever engineered this instrument clearly understood this, because it has a metal liner in the middle socket and the lower rail of the middle tenon has a metal sleeve. Unfortunately, the upper rail takes the brunt of those lateral forces, so it had worn down and there was a noticeable wobble. There are several ways to deal with this problem. Some techs wrap the rails in cork, but I don't like that because it doesn't seem to last. The ideal fix is to machine a new rail out of plastic, but for that you need a beefier lathe than I have, because you also have to cut the lower rail off the tenon in order to slip the upper rail on. I therefore went with the third option, which is to wrap the rail in silk. Silk is the preffered material for this process because it doesn't stretch like cotton (which ensures you get an even layer all the way around the rail). It also doesn't compress, so it can hold up against that lateral movement. Incidentally, the fact that silk doesn't compress is the reason a stuck silk swab can't be extracted by pulling harder on it.

The process of installing the silk wrap is actually pretty simple. You cut a strip of silk, making sure to follow the weft of the fabric. Then you tack it to the rail with a dab of super glue, and slowly wrap it around while following with thin super glue. The whole strip should be saturated with glue when you're done. This keeps it in place on the tenon and adds a little bit of reinforcement. Once it's dry, you can go around with a razor blade and cut off any excess. The silk will be stiff enough to cut cleanly.

After it's in place, you can file or sand the wrap until it fits snugly in the socket. This one required minimal fitting, and now it fits perfectly in the socket with no wobble. 

After that, I put the springs back on the upper joint, made final adjustments to key fitting, and started fitting and installing pads on the upper joint keys. More on that with tomorrow's post, which will focus on the same process but for the lower joint (this post is just getting a little long). But here are all the upper joint pads glued into their cups

And then on the 17th day, I padded. Here are the first two keys, the G and Bb, on the instrument at the start of that process. I anticipate there are between 10 and 15 hours of padding, regulation, key fitting, and other adjustments between me and a functional english horn.

Buffet English Horn Day 16 - 2/28/14

Busy day in the shop today, so all I really had time to do on the english horn was plate that new post and the Eb lever that I cracked and repaired last week. For plating we use a small Caswell Plug N'Plate. It's a pretty simple rig. You hook the cathode up to your part, and the anode in this case is a little chunk of silver on the end of a wand. The plating solution is a liquid with metal salts dissolved in it to make it conductive sot that electricity can pass between the cathode and anode, completing the circuit. As electricity flows, the silver anode oxidizes very slowly, depositing positively charged silver ions into the solution, which are then attracted to the negatively charged cathode, where they bond to the surface.
Normally to use the Plug N'Plate you would wrap the anode in a cloth that you then soak in the plating solution, then brush the cloth on the part you want to plate, completing the circuit. But these parts were small enough that I could just immerse them in the plating solution along with the silver anode.

It took a few tries to get things right. The surface to plated has to be very smooth and perfectly clean for the process to work. Any grease or foreign matter on the surface will prevent the silver from adhering. I had to degrease several times before the silver actually took hold.

When the part comes out of the plating solution, it's completely black. If you've done things right, though, you can wipe off the black crud and reveal the silver plating underneath. Here's how the post turned out. 

Here's a before pic of the raw brass finish for reference.

And here's the Eb lever from last week.

And a before pic. The difference isn't as noticeable in these pictures, but in person the raw brass really stuck out like a sore thumb.

Buffet English Horn Day 15 - 2/27/14

I was able to stay late at work tonight to fix the error I made yesterday in drilling the pilot hole in my new post. And by "fix the error" I mean "make a new post. I though it would go more quickly this time, but really it didn't. That's ok though, because (spoiler alert) the new post turned out super great. 

I had to start by resharpening the tool bit on my lathe, which was already dull the other day when I was working on the first post, and by now was in really bad shape. I'm still learning to sharpen bits, so it took me awhile, but after a few false starts I got the bit nice and sharp. 

I just turned the threaded section on the lathe this time, then did all the other shaping by hand with a file in the bench motor. Last time, I cut the post off the excess brass rod before checking the fit and position in the body of the instrument. That resulted in a lot of marring on the face of the post from where I had to grab it with pliers to thread it in. So this time, I checked the fit and position before cutting off the excess. That way I could just grab the excess rod with a pair of pliers and scratch that up without touching the post. I also drilled the pilot hole and spring hole before removing the excess this time, and I drilled the holes much more carefully and slowly. Here's the hole thing after drilling, right before I cut off the excess.

Then I used my tuba valve stem from the other day to hold the post in the bench motor while I further shaped it.

After shaping and sanding, I checked the fit one more time before countersinking the back of the post to receive the pivot screw head, and facing the front to mate with the key.

Here it is after facing, with the key up against the now flat face of the post. It fit perfectly!

With the key removed, you can see the flat face. I don't have a mill, so I had to get a little creative to figure out how to cut a smooth, straight face. I used a hinge tube shortener and it worked very well.

Here's a final shot with the original post, the new post after buffing (it's ready for plating!) and the piece of brass rod I used to make it.

After that, I was on to wood working on the lower joint. Careful checking revealed that I needed to be a little more fastidious than I was with the upper joint tone holes last night, so I really took my time to establish a flat on each tone hole, face the outside with my new facers, then chamfer the inside with a set of pad seat reamers. I checked each one multiple times with a light in the bore, a 10x eye loupe, and a faced brass rod for reference, and I'm happy with how things came out. If I studied the results correctly, then padding should be relatively smooth this weekend.

Tone hole facing was the first half of wood working I had to do on the lower joint, and the second half was repairing that nasty crack near the C# tone hole where a post had jammed. I started by filling the gaps and pressing the wood back into its correct shape as much as possible. That was followed by sanding the surface smooth and adding more glue to fill the remaining cracks. Alternating those steps a few times gave me a nice smooth surface with a minimally visible repair. I suspect that after the wood is oiled, things will blend a lot more smoothly.

Here it is in progress.

And after sanding and smoothing.

And for reference, here's what it looked like before.

Now the lower joint is in the immersion oiling tube, the upper joint is drip drying, and tomorrow I should be able to fix the split in the upper D ring and plate the keys that need it. I'm (hopefully) only a few days from having a functional english horn!

Buffet English Horn Day 14 - 2/26/14

Today I started facing tone holes. I found the perfect glue to use for sealing the tone hole rims - a superglue that's not too thick or thin, so that I can wick a thin bead all the way around the rim. The facers seem to be working well, too. I got all the tone holes on the lower joint leveled and then dropped that joint in the immersion oiler. Tomorrow I'll take care of the lower joint tone holes and deal with that crack near the C# hole.

I also installed the new post I made and got to check its fit.

I don't know why that picture looks so washed out. Oh well. The post fit well and was the right height, so that was great. Unfortunately, while I was drilling the pilot hole for the pivot screw, the drill bit wandered a little bit, and I ended up with a hole that wasn't centered. So it looks like I'll have to start over with a new new post. This time the job should go much more quickly since I've already done it once.

Buffet English Horn Day 13 - 2/25/14

I got my tone hole facers today!

The machine shop I used was Peterson Machine in Chester Springs, PA. The machinist there, Tim, was great to work with and his work turned out very nicely. Not only that, but turnaround time was quick and he kept me in the loop. He said he measured the angles of all the tone holes and they weren't all the same, so he sort of averaged them out to make the facers. I'll be trying them out tomorrow and hopefully they match!

Buffet English Horn Day 12 - 2/24/14

This morning I threaded and cut off the post I started yesterday, then made a threaded jig to hold it out of an old tuba valve stem. Now, once I have the pivot screw hole drilled, I can polish and buff the whole thing without scouring away my fingerprints!

Later in the day I had a chance to talk to the machinist working on my tone hole facers, and he said they should be done tomorrow. Buoyed by that good news, I spent the evening corking keys.

Buffet English Horn Day 11 - 2/23/14

Today's job was making a new post. One of the posts on the lower joint looks like it was cut or ground down at some point, so it doesn't contact its key at a nice square angle. Unfortunately, I don't have the body of the english horn (it's still with the machinist making my tone hole facers), and I left the thread die I'd need at work. But that's okay, because I could still get some work done.

This is my lathe, a Unimat that I rebuilt last year. It's not perfect, but it runs pretty well and is perfect for working on small parts, especially something like this where I just need to use it to rough out the shape and then finish it with a file and sandpaper. It's not great at creating a nice smooth finish, although that probably has more to do with my meager abilities at machining and tool bit sharpening than it does with the machine's limitations. I am getting better though, and in the future when I can purchase a larger, more precise lathe it will provide an opportunity to continue developing those skills.

I used the lathe to turn the end of the brass rod down to the diameter needed for the post threads. Like I said, I don't have the die to actually cut the threads, but that'll be a quick process now that the rod is the correct diameter.

You can see above that I also used the lathe to rough out the shape of the post, but that put me at the limitation of my tool bit and skills, so from there I moved on to filing with bench motor.

Here it is, with the curves smoothed out and closer to the finished shape.

Finally, I roughed out the sphere at the top of the post, but left everything attached to the rod so that tomorrow I can grip it in the bench motor while I cut the threads. After that, it's just a matter of lining it up in the body, marking and drilling the screw hole, tapping the screw hole, and plating it.

Things always look rough after filing, but a little sanding and polishing left a very nice finish, which I can further smooth by buffing later.