Manufacturing Horn Bearing Plates

This sad old Gretsch horn (as in the guitar maker!) came in to the shop from a local charity that we do work for. Two of the bearing plates were just missing and while it was well beyond the value of the instrument to make new ones, I was interested in doing it for pro-bono practice. At worst, I'd mess it up and they'd have a horn that was no less functional than when it came in. At best I'd get it right and they'd have a horn that was marginally more functional than when it came in. Marginalliy because, you know, it's a Gretsch horn.
A bearing plate is a pretty simple shape to machine, the hardest part being to bore out the spindle hole so that the spindle will be tight but not binding. A hole that's a little tight can be lapped in to make a smooth fit, but a hole that's too loose is useless. I threw out a few practice plates before getting two that worked.

1" brass stock would have been ideal to work with since the plates measured just under an inch at their widest, but I was out and only had a day to work on this, so a couple thick brass slugs, about 2.5" diameter, had to be turned down quite a bit. After turning a couple duds, I figured out that it would be best to turn the spindle hole first. If it turned out too large, I could cut off and start over, without having invested any time in turning the other parts of the plate. Here the slug is being center-drilled to start that hole.

After center drilling and through-drilling the hole with a drill bit that was slightly undersized to the final target diameter, it's bored out to pretty close to that diameter.

Checking the fit of the spindle in the hole. This one was a little snug, which is great because it can be lapped in later.

Turning the under-side of the plate. The raised area around the hole is the bearing surface that will make contact with the bearing surface on the rotor. The rotor only contacts the plate on that narrow surface and inside the spindle hole.

The underside of the plate, on its way to being finished. The thick shoulder running around the outside edge had to be thinned out to allow the plate to sit at the right depth in the rotor casing. I did that by repeatedly checking the fit on the instrument and removing small amounts of material until achieving the right fit.

The top of the 2nd plate, with a big ugly 2 stamped in.

All set to go. The 1st and 2nd casings are new, the 3rd is the original I used as a template. I didn't turn in that decorative step on the new ones just to save a couple minutes. Without witness marks on the new rotors, they had to be ported by looking down the slide tubes and sighting the alignment, then trimming the bumpers as needed. That's how I port all horn rotors anyway, though, since the witness marks aren't always perfectly aligned, especially on mass-produced student level horns.

Clarinet Tenon Rails

The rails are the thin strips at either end of a tenon. While the cork creates an airtight seal and prevents the joints from slipping apart once assembled, the rails provide structural support and prevent wobbling. This is perhaps best demonstrated on clarinet center tenons, which must bear a lot of stress from the weight of both the upper and lower joints. Ideally a long tenon would distribute that stress, but the center tenon has to be made relatively short because of the placement of the tone holes on either side. It's not surprising, then, that we see a lot of older clarinets with worn down rails on the center tenon, especially wooden instruments. A worn tenon will invariably wobble, causing the bridge key regulation to go in and out. It also just feels weird and wrong. 

This clarinet had an especially bad center tenon. Beyond the natural wear, I suspect someone got overzealous and sloppy with their sandpaper when replacing the tenon cork at some point. The rails were almost gone, so the tenon was pretty much a uniform diameter. Sometimes silk-wrapping a tenon can address worn rails, but you need something to start from in order to do that. The only option here was to turn and install new rails, which is a more stable and accurate repair anyway.

After cutting away what was left of the old rails - and a little more on the lower end to create a nice square edge for the new rail to butt against. That groove on the upper end was for epoxy to get in and adhere, but I don't think I'd do it again as it makes the tenon a little weaker.

The new rails, cut from ABS plastic. The lower one is thicker.

Installed with epoxy and ready to go.

After corking and completing the rest of a repad. No wobble anymore!

Antique Cornet Leadpipe

I get a few instruments a year from a player in a Civil War band that uses period instruments. This cornet belonged to another band member and was missing its original detachable leadpipe. They'd been using one scavenged from a flugelhorn for some time, but it didn't quite fit and caused the instrument to play out of tune, so he requested a new one be made for it.

I was able to pick the brain of Mark Metzler (http://www.metzlerbrassrepair.com/), who has been an invaluable resource working on these antique horns in the past. Since I didn't have an original leadpipe work from, he provided some advice, like the fact that the tubing in the leadpipe would be cylindrical, not conical. He also on gave some tips on determining the right length and diameter of tubing to use, but ultimately I had to do a bit of trial and error work, mocking up parts held together with teflon tape, testing the instrument and taking notes to come up with the right dimensions. I found a little help from the website for Olde Towne Brass, a period brass band that lists many of the instruments in their inventory along with pictures. They have an identical instrument by the same maker (Hall and Quinby) with the original leadpipe. Looking at their photos provided a starting point for determining the length of tubing needed. I tried several different pieces of tubing, and ended up using a piece of the cross-brace from a trombone handslide cut to length. The diameter was just right, and the finish even matched the rest of the instrument. 

The receiver on the instrument had the same taper as a trumpet mouthpiece receiver, so I was able to cut and drill out the shank of a trumpet mouthpiece to make that end of the leadpipe. 

The shank of a trumpet mouthpiece, held in a scrap receiver taken from a junk trumpet, is held in the lathe ready to be drilled out to match the bore of the leadpipe tube. The front end was then drilled out further so that the leadpipe tube could slide in and be soldered in place.

The owner wanted the mouthpiece end of the leadpipe to accept a modern cornet mouthpiece, so I was able to put a generic cornet receiever there. With everything soldered up and buffed, the final product looked pretty good.

Well, maybe a little too shiny, but time will take care of that.

Manufacturing a saxophone neck socket

This was my first time making a neck socket, for a Conn New Wonder tenor sax that came to me for an overhaul. The original one had been completely trashed over about 100 years of use and abuse. The socket was severely out-of-round, the slot had been enlarged with what I can only assume was a dull lawn mower blade based on the level of precision, and the spud that holds the screw was chewed up. The tenon on the neck was, surprisingly, in good condition, but I could see no way to salvage the socket to make it seal with the tenon, so it was time to fire up the lathe.

Manufacturing the socket itself wast't a particularly complex operation. Some people prefer to start with solid brass rod that they face, turn, drill, and bore to the correct dimensions. For my first try, I decided to skip the drilling step and start with heavy-wall brass tube. Onlinemetals.com carries such tubing in a variety of sizes and lenghts. For this instrument I got a piece with an outer diameter of 1.25" and an inner diameter of 1".

I made two sockets that ended up on the scrap pile as I got my feet under me, but the third one fit the neck very well. It's probably due to my frustration over those first two that I neglected to take any pictures of the process, but here's a shot of the completed socket:

Turning those ornamental grooves at the bottom (to match the original) was probably my favorite part. The slot in the socket isn't cut until everything is assembled, which meant I had to make the spud (the part that holds the screw) and braze it on first. Making the spud and shaping it involved a little turning and a lot of hand-filing to get the right shape. Then I drilled a hole all the way through, further drilled out one half to be larger than the diameter of the screw, and tapped the other half so the screw could thread in. The toughest part of that process was making sure those areas actually met in the middle of the spud, so that when it was cut in half after brazing, one side would be fully threaded and the other side would have no threads.

Cutting the slot was done first with a jeweler's saw to ensure a precise, straight cut. Then that was widened with a Dremel tool and a cutoff wheel at low speed. The whole socket was then soldered to the instrument, buffed, and lacquered. It's easy to see that the color doesn't match the lacquer on the rest of the instrument, which has had decades to age and develop a nice dark color. That's something I'm determined to get better at. Color matching can be acheived by either darkening the brass with a chemical treatment or tinting the lacquer, which is currently beyond my abilities without the use of a compressed-air driven lacquer gun. This customer was OK with the colors not matching, and spraying clear lacquer over the socket ensures that it won't tarnish and end up looking worse than the rest of the instrument.

This project was a learning experience, and going over the results with a couple other technicians has already given me some tips to employ next time the need arises.

Bushing a Piccolo Post

This piccolo came to me for a repad from another music store, and was curiously already disassembled when I received it. Only after starting work did I discover that one of the trill key posts was stripped out, so its pivot screw wouldn't hold in place. I suspect that may be why it was taken apart and aborted before reaching me. Bushing the post was a fairly quick and straightforward job.

First a small piece of brass was turned, faced, drilled, and tapped to make the bushing.

The rib holding the posts was removed from the body, and the offending post was drilled out to receive the bushing.

The brass bushing was tinned - solder was flowed on to it then wiped off - before installing it in the post. Tinning the part leaves a very thin layer of solder bonded to the base metal, so that in this case it could be installed in the post and the parts heated without having to flow any additional solder that might bleed into the screw hole. Once the parts reached the flow temperature of the solder, the bushing would be bonded to the post. 

The bushing is soldered in place. I used a 94/6 tin/silver solder alloy, which is stronger than tin/lead alloys, especially when using such a small amount on a small contact area. The reason for soldering from this end is that it's easier to set the faced end of the bushing to the desired counterbore depth in the post, cut off the excess flush with the edge of the post, and clean up the edge. If done from the other end, the the bushing would have to be counterbored after cutting off the excess.

After soldering and cleanup. The bushed post is the one on the left.

From the other side. This is the side where the point of the screw will come out and engage with the key.

After reinstalling the rib on the body and checking the fit of the screw, it was necessary to counterbore the bushing a little bit more, which is simple when there's already a counterbore established to guide the cutting tool. 

Since the bushing is completely obscured by the key on one side and the screw head on the other, this is a completely invisible repair.

Conn 26M VIII Alto Sax overhaul

It's been awhile! Seems like there hasn't been any time to post lately, and there still isn't, so I'm just checking in with a few shots of a Conn 26M VIII alto sax that I had the privilege of overhauling last month. If you want to read a well-written and informative article about the 26M, there's one here on Matt Stohrer's blog. Matt's posts are always thoughtful and insightful. Anyway, here's mine:

This instrument was in beautiful condition, and was brought in by the son of the original owner. His father passed it along to him when he was in second grade and it was the first saxophone he played. SECOND GRADE! He must have been the most coordinated eight-year-old who's ever lived, because this thing had no dents, no significant misalignment, and no missing parts. All of the (numerous) adjustment plates were intact and only a couple were frozen, and those broke free with a reasonable amount of effort. The only notable damage was that several of the pearl rollers were cracked and broke apart from being rusted on their rods.

The overhaul was a big job, but once all the pre-padding work was done (cleaning, straightening the body, aligning posts, fitting keys, leveling and dressing tone holes), the padding process was enjoyable, and the setup after that was downright idyllic. Need to adjust a regulation? There's a screw for that. Want to to change the key heights of the entire lower stack? There are screws for that. Want to change the relationship of the touchpieces in the left hand pinky table? That's more complicated than just turning a screw, but a hell of a lot easier than any other sax. This instrument had a steep learning curve, and I don't know how long it will be until I get to apply what I learned to another 26M, but it sure was a lot of fun.

Sleeving the Upper Joint of a Clarinet Part 2: Graphite Banding

With the sleeve in place and the bore restored to a consisent and concentric shape (see previous post) I moved to the outside of the instrument. The two enormous cracks running down either side of the upper joint could still leak or even continue to grow, especially with a plastic liner that expands at a different rate than wood with temperature and humidity changes. While I usually choose to pin cracks because of the relative ease of installation and minimal cosmetic damage, that wasn't a feasible option in this case. Drilling holes for the pins would have required going through wood, then plastic, then wood again, and since different speeds are necessary for drilling plastic and wood there was a good chance of either overheating/burning the wood or melting the plastic. So installing bands, while more cosmetically disruptive, made a lot more sense. If you saw the previous post about this instrument, you saw that it came in with metal bands installed, which is an older method of doing this repair. However since the development and proliferation of graphite ribbon, sometimes also referred to as carbon-fiber, that's become the preffered material for banding. It's easier to work with and slightly more flexible than nickel, so there's less chance of it causing the bore to constrict as the wood expands and contracts over time (as had happened with this instrument).

Ideally I would have cut the channels for the bands deeper than in this example, so that they could be installed below the surface and covered with mixture of super glue and grenadilla dust, a technique I first heard about from a technician in the UK named Chris Peryagh. But since a lot of wood had already been removed from the inside of this instrument, I tried to minimize the depth of the channels and therefore keep as much wood as possible between the band and the sleeve.

Before cutting the bands, though, the top three tone holes had to be re-drilled since they were covered up by the sleeve. Cutting a new tone hole would ideally be done on a mill to ensure an absolutely straight and level cut with an even pad seat. In this case since the top half of each tone hole was still intact I was able to use that as a guide for drilling out the sleeve on a drill press.

Re-drilling the C trill tone hole. Do you like my expertly constructed clamping jig?

Wax is applied to the outside of the joint to prevent epoxy from sticking to the surface. That's the goop you can see in the top couple tone holes.

Next the channels were cut on the lathe to .040” deep. Epoxy will adhere in the channels since the waxed area was cut out.

Strips of graphite are pulled from a ribbon, approximately the same diameter as the channels. They're coated in a generous amount of plain old 2-ton epoxy. The strips are laid into the channels and pulled snug but not tight, to avoid constricting the wood. Although, that's less of a concern on this instrument since the plastic liner is less likely than wood to buckle.

After the epoxy is dry the excess is trimmed on the lathe, but not all the way to the surface. The outside of an instrument is rarely concentric with the bore (eccentric), and that's even more true of this instrument than most, so final cleanup will be done by hand.

The rest of the excess is filed off, then sanded until the bands are flush with the body of the instrument and the surface is smooth.

Finally the joint can be oiled. This is only done after the bands have been installed so that the oil won't interfere with the adhesion of the epoxy. After a week in the immersion oil bath, this joint is ready for key fitting and padding.

The joint was immersed in oil for a week, then allowed to dry for about 3 more weeks so it had a chance to fully absorb as much oil as it needed. This is how it looked at the end of that process.

After all of that was done, I ventured back in to Philadelphia to visit Mark Jacoby again, who has a set of factory reamers designed especially for cutting the necessary tapers in a clarinet. Actually, before taking on this project I didn't know that the upper joint of a clarinet is tapered at all - another thing I learned from this process. On this instrument, as with many others, there's a slight reverse taper in the top of the upper joint that transistions into a short straight section, then back out to a taper. Since the bore of the insert was cut straight on the lathe, reaming restored that original taper. No pictures of that process, sorry.

After installing all new pads and corks and making a lot of fine adjustments, this instrument has a new lease on life.

One last before-and-after, how the instrument looked when it came in, and just before packing it up in the case.