Antique Cornet Lever Bridge Repair

This antique cornet came across my bench in need of some...remediation. The levers and their clockspring mechanisms are mounted on a bridge, which is attached to the instruments by two feet. One of the feet had broken off and been replaced in a manner that could charitably be described as "haphazard." It was an inexplicably scalloped piece of brass, attached with generous amounts of solder and reinforced with some wire that may have once served a real purpose somewhere as a paperclip. I cut and shaped a new foot from brass, and then affixed it to the bridge with a small handmade brass rivet. A remnant of the original foot provided evidence that this was how it had been attached by the maker. A drawback of using a rivet rather than a screw is that it's more labor-intensive to install and can't be removed without destroying it, but the advantage is that it's very long-lasting and can't be jostled loose over time.

Here's the foot it had when it arrived on my bench, after I'd removed the huge glob of solder that had held it on the instrument, along with a few wraps of wire. The impression from that wire can be seen at the bottom of the photo in some excess solder that had flowed along its length.

Another view of the previous repair. Surprisingly (or maybe unsurprisingly because of how much solder and wire was involved) the joint had held and seemed pretty strong.

Here's the new foot from the underside, showing the rivet that holds it on to the bridge.

 

The new foot from above, contoured to match (well, sort-of match) the style of the other braces on the instrument. The circle visible on the end of the bridge is the top of the rivet.

Side view of the new foot.

All set to go back in to service!

Laubin English Horn Hinge Tube Insert

This is the C key from the upper joint of a Laubin english horn, in for an overhaul. Since tight key fit is essential to stable padding when working with cork pads, I spend a lot of time in my overhauls fitting keys to remove any "slop" in the mechanism. A lot of times that involves sweding the tube on the key to shrink it a little bit, and make it fit more snugly on the hinge screw. However, this is one of several keys on an oboe that can't be swedged, because of the long arm that's attached along its length. There's not a good way to get a tool in there to shrink the tube if you don't have access to the entire circumference of the tube. If you look at the end of the tube on this key, you can see that it's been "wallered out" somehow, so the diameter is way too large on that end. That allows the key to wobble on the hinge. The normal way of dealing with this would be to make an oversized (greater diameter) hinge screw and ream the inside of the tube to fit it, thereby enlarging the tube enough to cut out the "wallered" section. However, I'd already made an oversized hinge screw for the entire left hand section on this instrument. There were other keys in that stack had also been loose, and they all fit beautifully after reaming and lapping to the new screw. However, this one was still loose. Not wanting to make an even larger screw and ream all the other keys again, I decided to make an insert for this tube that would allow it to fit snugly. 

The rough surface on the inside of the tube is where it was still loose on the oversized screw. The reamer that I ran through didn't even touch that area because it's so blown-out.

This thick-walled brass tube has a very small center hole, much smaller than the diameter of the hinge screw. After the insert is installed, that hole will help guide the reamers through as I gradually enlarge it to the correct size. It's being turned down to a diameter that will fit in the tube on the key.

Here's that same piece after being cut off and cleaned up in the bench motor.

The piece was "tinned" to make it easier to solder in place. The whole part was heated and solder flowed over the surface, then the solder was wiped off while still liquid, leaving a thin layer on the surface. When soldered in to the key, solder will flow much more easily over this surface than it would the raw brass underneath.

After soldering the insert. The end of it sticks out beyond the end of the key tube, and will be trimmed off later. The finished insert was intentionally made larger (greater diameter) than the hole in the key, and the key was reamed up to match it. That created a nice clean surface inside the key for soldering, and the inner diamter of the key tube was made uniform to match the outer diameter of the insert.

Reaming the insert up to size. Progressively larger reamers are used, each one removing a few thousandths of an inch of material.

The last reamer sticking out, having passed all the way through the insert. The chips of material it removed are visible on the end.

The interior surface of the insert is much smoother and more uniform than the original key tube.

After a little bit of lapping to remove to make the fit smooth, the hinge screw fits nice and snug in the key now, with no wobbling on either end.

Loree Oboe Overhaul Time-Lapse Video

I've been wanting to do a time-lapse of a major repair for some time, so when this oboe came across my bench it seemed like the perfect opportunity. This is an AZ series Loree oboe from the late 1950's that hadn't been serviced in some time, so it needed a lot of attention. 6 minutes is probably a bit too long for a time-lapse, but the job took 20+ hours so I cut out as much as I could. That means a lot of little steps have been left out and some of the tasks that are shown will appear simplified. This video doesn't begin to show the amount of fussing and fiddling that goes in to every part of a comprehensive repair, but does give an idea. Most of the steps are directed toward ensuring that the pads are dead level to the tone holes and that they will close exactly the same way, in exactly the same position, with exactly the same relationship to other keys, every time for hundreds of thousands of repetitions.

That baking soda bath to remove tarnish was somewhat effective, but this was my first time trying it and I'll need to tinker with the process to see if can be improved. There was still a lot of polishing to be done after that.

The musical accompaniments are Perpetuum Mobile and Trish-Trasch Polka, both by Johann Strauss II.

Oboe Octave Touchpiece Extension

This Loree oboe belongs to a local university, and is in use by a student who has difficulty reaching the thumb touchpiece for the octave key. Her professor asked if an extension could be made to improve the ergonomics, based on one she'd had made by another technician for another oboe. Making an extension plate is simple enough - it's just a piece of nickel sheet with the edges rounded over to remove any sharp burrs, and curved a little bit to match the contour of the body and fit in the case. In most cases, it's then soldered or brazed on to the original touchpiece. However, with this being a school-owned instrument, the extension will need to be removed at some point so that another student can use it. Removing a soldered or brazed part would require bringing it back to the shop and would leave residue that would require some amount of cleanup. So it made more sense to manufacture an extension that could be affixed mechanically, in this case by screws.

The extension needed to add at least 3/16" to the left side of the touchpiece, and I chose to make it a little longer than that just to be safe.

The process of making the extension isn't very interesting. A template was marked out on a sheet of nickel, cut out, and the edges sanded to achieve the right shape and contour. Then it was formed into a curved shape to somewhat match the curve of the instrument body. Holes were drilled in the plate where it would meet the underside of the touchpiece, then matching holes were drilled and tapped in the touchpiece. A couple of 2.0x0.4 metric screws were modified to fit, and the part was ready to install, which was as simple as screwing it on. That's it! The next few pictures just show the completed part.

The extension in place. It's thinner in the area that sits under the touchpiece, to allow for adequate travel of the key.

A view from under the key. The extension can be removed by anyone simply by unscrewing it.

With a cork on the extension, the screws are hidden. The cork contacts the body when the touchpiece is depressed to control key travel. When the extension is removed, a piece of cork affixed directly to the bottom of the touchpiece will serve the same function and cover up the screw holes, so there will be no visible evidence that the extension was ever installed.

The touchpiece with extension mounted on the instrument. 

Resetting a Buffet Clarinet Post

This Buffet clarinet came to me twice in the same year because the hinge screw on the Side F# key had snapped off at the threads. The first time I simply manufactured and installed a new screw, but I did notice at the time that it felt a little tight going in. This time I investigated further and discovered that the underlying problem was a misalignment between the holes in the threaded post and the unthreaded post, which hold the screw. The hole in the unthreaded post was angled too far downward, so that when the screw was fully inserted, that post pushed down on it while the threaded post pulled up on it. The screw broke at the end of the threads because that's where the diameter is thinnest and weakest. The fix would be to change the angle of that hole.

The way I saw it, there were three potential ways to address the issue:

1) Raise the unthreaded post so that the angle of the hole was in line with the threaded post. 

2) Drill out the hole in the unthreaded post, then solder in a bushing at the correct angle, using the screw as a guide. 

3) Completely fill in the unthreaded post with a soldered plug, then re-drill it at the correct angle using a post-drilling jig.

At the time, I didn't have a post-drilling jig (I do now!) so option 3 was out, but I did have a drilling jig for the body, as detailed in a previous post, so I chose option 1 to give that tool a workout, though option 2 would have been just as good.

The first step was to remove the post and drill out the post-hole in the body to remove the threads. Because the post's height and radial alignment are both dictated by how far it's threaded in to the post-hole, and because both of those variables have to line up at exactly the same point, new threads would have to be cut into a bushing, then aligned on the body.

The small hole at the center of the picture was the post-hole. This is after it was drilled out.

Below is the bushing installed on the post. It's just a piece of ABS plastic, turned on the lathe and threaded.

The post was threaded into the bushing before installation.

The bushing and unthreaded post were glued in to the post-hole in the body together, using the screw to properly align things with the threaded post. Once the glue set, the pad had to be replaced to account for the slightly different angle at which the key now meets its tone hole, and the problem of the broken screws should now be permanently resolved.

The repositioned post is at the center of the photo. Looking at the base, you can see that it's now raised slightly off of the body. It's not cosmetically perfect, but probably not the kind of thing you'd notice unless you were looking for it.