1978 Besson New Standard -- Valve Guide Wear / Noise

[ghmerrill]

I recently made this conversion on my 1971 Besson. For me the hardest part was getting the old guides out. The guide in #1 was already loose, and #2 unscrewed easily. However, #3 fought me all the way out, and #4 was totally stuck. I broke the top off of the old #4 tacquet and ended up having to drill out the old one, which was a little stressful (no going back now!).

I'm glad this worked out so well for you. Broken fasteners are a real pain. Three comments:

1. Very often (almost always?) the application of PB Blaster to a stuck threaded fastener will free it up to the point that it can easily be removed. Sometimes this requires repeated daily applications over a period like a week (especially for fine threads or in cases of significant corrosion). I have a problem like this with a stuck valve stem that I'm just working on slowly over time. I just about always use PB Blaster as a precaution on any old fasteners.
2. Remember that the "best practice" in drilling out any broken screw in circumstances like this is to use a left-hand bit in a reversible drill or drill press. This serves two purposes. First, it may end up acting as an "easy out" and actually unscrew the bolt as you're attempting to drill it out. But second (and more important) it will avoid the opposite effect of driving the broken screw stub into the hollow piston -- where it will rattle around for the rest of eternity.
3. If you get a fastener partially unscrewed and then it breaks, leaving a bit above the surface, an often effective approach is to use a Vise-Grip of one sort or another to clamp onto that stub and very carefully continue to unscrew it. The Vise-Grip, unlike pliers, won't slip; and you can apply a huge degree of torque to the broken fastener shaft. This is difficult on very small fasteners, but is still worth a try if there's enough of the shaft available.

[daniel76309]

Thanks.

Interesting you mentioned PB Blaster. I had heard good things about that stuff so I bought a can a few weeks ago. However, when I got home, juggling several things getting out of the car I ended up dropping it on the ground, and the nozzle broke off, rendering it useless.

I have left hand drills and screw extractors, but none nearly small enough for this. I could grab onto it with a small pliers. I have Vise Grips, but I honestly don't think they would have helped because the limiting factor here was the softness of the brass--i.e. whatever I grabbed onto would break away before it would unscrew. It also did not work to cut a slot in it so I could engage with a small screwdriver--it also just broke away.

I ended up drilling all the way through the screw with a round dental type bur in a "Dremel", and then picked out the remnants with a small screwdriver. It was no fun, but it worked out ok.

I may have dinged up the internal threads a little, but it really doesn't matter. The nylon screws have threads on them, but I think they are a finer thread than on the piston. The nylon screw seems a little oversize and it seems that the threads are there just to pull the screw into the hole as it is compressed--i.e. it does not seem to be a precise threading the way the original brass screws were. I also think that if/when the nylon screws need replacement, I will end up having to drill them out again as they fit very tightly in the hole and are even softer than the brass.

[coolguy684]

Would any harm be done by using a candle or lighter to burn the broken remains of nylon left? I'm not sure if it will melt out like wax or if it will leave an extremely hard to remove residue.

[tampaworth]

I recently made this conversion on my 1971 Besson...in the end, it works great and the valves are nice and smooth and quiet.

Great job and an interesting experience for us all to learn from. My old brass guides came out easily, I was lucky. Enjoy the smooth action!

[bbocaner]

I wouldn't -- a quick google search just told me that the melting point of nylon is actually hotter than that of solder. You wouldn't want your piston to start coming apart while you were trying to melt out scraps of nylon. It'd probably just make a big sticky mess that would be even harder to remove, as you suggest.

[coolguy684]

I suppose then that it will be a DIY thing when you put them in, but when you need to change them out you might need a trip to the tech to drill out the broken of nylon. But that should be fine, guides should be able to last a year or more, and I would hope that a chem/ultrasonic clean would have happened within that time!

[ghmerrill]

Would any harm be done by using a candle or lighter to burn the broken remains of nylon left? I'm not sure if it will melt out like wax or if it will leave an extremely hard to remove residue.

The same thing occurred immediately to me, but I am quite leery of it. First, plastic doesn't act like wax when you melt it. It doesn't actually flow much in a lot of cases and it starts to burn pretty readily. So I'm skeptical how successful this approach would be. But you could always experiment with it in a test situation before trying it on the horn itself. Second, melted plastic is really sticky. It would likely liquify to at least some degree and then just sort of stick in a puddle, or even get sucked into the hole. Still, worth a test.

[tampaworth]

The nylon screws have threads on them, but I think they are a finer thread than on the piston. The nylon screw seems a little oversize and it seems that the threads are there just to pull the screw into the hole as it is compressed--i.e. it does not seem to be a precise threading the way the original brass screws were.

Thanks to daniel76309 for this observation. After reading his post I decided to use my left over "metric" plastic valve guides and replaced the metal guides on my older Cleveland 623 baritone (which I wouldn't think is anywhere near metric). A great fit ... nice and tight once torqued into place. A 90 year old horn now with smooth and quiet valve action. Just some info for those with older American horns with metal tacquets and valve guide noise should you want to take the plunge.

[coolguy684]

I had 2 tacquets pretty severely stuck. soaking the top part of the pistons in WD40 and some minor pliar wrestling did the trick.

[ghmerrill]

Where are people getting these plastic valve guides (did I miss this information in the thread?)? And what sizes do they come in. I'd be interested in getting some that might fit my Buescher tuba before I go to the metal ones.