 The Clarinet BBoard
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Author: BobD
Date: 2003-03-06 14:44
Having damaged a Buffet "rod screw" removing it from a damaged key I am now going to try to make my own, being a naieve amateur repairer. I did manage to find a mini metric "button die" at Micro-Mark but they were out of an appropriate size brass rod. I thought I'd try putting threads on brass first before I try drill rod. But the thought struck me "why don't they make rod screws out of brass anyway since it's easier to machine?" Any comments or hints will be appreciated.
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Author: JMcAulay
Date: 2003-03-06 15:53
The rubbing of brass-against-brass is pretty terrible, because minor corrosion problems can cause things to seize up totally. Rusty iron is far from the worst thing in the world to have moving against brass.
Keywork of most good Clarinets is made either of brass or, more commonly, from "german silver," also called "nickel silver." This alloy is basically brass (copper/zinc) with added nickel, although some german silver is sold which may contain tin, or even traces of other metals. It is stronger than brass (with lower temperature coefficient and electrical conductivity). Its corrosion resistance is better than that of brass, but its corrosion products are similar to those of brass. Thus a rubbing surface of brass-against-nickel silver is not much better than brass-against-brass.
Consider that mechanical timepieces, from large clocks to small watches, have for centuries used brass plates and iron/steel moving parts and screws. A very tiny amount of oil keeps things going smoothly, and repairs are facilitated. Even if a screw does become stuck, immersing the assembly in an alum solution will dissolve the screw sufficiently to remove it, while the brass will not be damaged.
Regards,
John
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Author: ron b
Date: 2003-03-06 19:43
Based on my meager experience, Bob, I'd like to emphasize, along with John, that brass or nickel silver is just too soft for use as screw material. It doesn't wear well and the tendency to break, rather than spring, is great. Very old woodwinds used brass pins but these were rather quickly abandoned in favor of something more durable.
Hinge (rod) screws and pivots in recent times (past hundred years or so) are traditionally made of steel (drill rod) because of its hardness. Brass against brass, as John so well points out, is a very poor combination that will deteriorate rapidly under the best of conditions. The only instances I've seen first hand are on cheap 'instruments' that come, by whatever route, from mainland China (or, India?). Attempting to back out a pivot or long screw without 'stripping' the slot or breaking the head is nigh impossible - sooner rather than later. Reputable techs will not work on them. (Take it back to the dealer).
Brass, or brass alloy, may be fine for threading practice but I wouldn't seriously consider using it in a real hinge or pivot application. At best, it would be a Very temporary fix. Well, really, I can picture no situation where I could do so with a clear conscience.
(P.S. -- Brass is not easier to machine by the way
Post Edited (2003-03-06 20:45)
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Author: Gordon (NZ)
Date: 2003-03-06 19:54
Also:
- Technicians have enough problems with bent pivot tubes and the occasional bent rod. If the rods were a copper alloy they would bend as easily as the tubes.
- The quickest technique for straightening bent tubes RELIES on the rod being a lot stronger than the tube.
- If a screw becomes jammed through bending or corrosion, and it is made from brass, the slotted head will almost always be destroyed before the screw comes out.
- Occasionally a corroded rod needs to be punched out of t pivot tube. If it were made from brass then it would distort and jam more, before it budged.
But 'nickel silver' rods, un-threaded, and often bent over double at the head end, are often used for bassoons. Strange, that! Also for keys on larger recorders.
For pivot point screws: Often a technician has good reason to tap a key with a (soft) hammer, or put bending forces on a key while it is on the instrument. Steel point screws can tolerate this. Brass alloys would bend.
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Author: Gordon (NZ)
Date: 2003-03-06 22:55
John wrote
"Even if a screw does become stuck, immersing the assembly in an alum solution will dissolve the screw sufficiently to remove it......"
I've never tried that John. How long would it take for alum to remove a 20 mm steel pivot rod from a pivot tube? Is this a solution of alum in water? How strong? Does it work on a HSS tap?
Thanks
Gordon
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Author: BobD
Date: 2003-03-06 23:07
Thanks to you guys for your prompt and thorough responses and I know from prior posts that you are experts and know what's what. I do have a couple of comments:
1. Since most keywork is plated with nickel or silver a brass screw would be rubbing against the plating rather than the base metal which is usually nickel silver. Right?
2. I find it hard to believe that drill rod is easier to machine than brass (or no more difficult) but let's face it I haven't made any real life comparison.
3. The horn I had the problem with was my own Buffet E-11. When I started to remove the screw it wouldn't budge and it was only after applying heat and rust remover carefully with no progress that I noticed that the key tube had been bent slightly thus binding the rod. How the key tube got bent in the first place is another story. Thanks again. Bob
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Author: jim lande
Date: 2003-03-07 03:06
As you say, some great information above.
Does Alum destroy the pivot screw or threading on a rod screw?
You can buy various tools to check the size of the rod and the precise threading. They may all look the same, but they are not. Needless to say, close doesn't count. There really are a lot of possible combinations. Once you know the right one, you can buy the drill rod & correct die.
Somebody recently explained how to get the bend out of a hinge tube: Take slightly undersized drill rod, put a slight kink in it, mount it in a drill, and then run it back and forth through the tube a couple times. I have tried it with success. (Previously, I have spent a lot of time with pliers & a hinge tube file.
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Author: JMcAulay
Date: 2003-03-07 04:35
Gordon (NZ) queries:
"How long would it take for alum to remove a 20 mm steel pivot rod from a pivot tube?"
I have no idea, as I've never tried it on a Clarinet pivot rod. It's an old watchmaker trick for removing a stuck screw. A pivot rod would likely take a very long time, as the solution would only be able to penetrate well into the tube after the ends are freed. Hence, the ends might free rather quickly, but things would progress rather slowly through the length of the thing. By the way, I was *not* recommending this for Clarinet repair (although it might work), just mentioning its application to very small parts such as found in watches.
"Is this a solution of alum in water?"
Yes.
"How strong?"
I don't recall. You might check some watchmaker references. Fairly basic ones should have this information. Or ask your local watchmaker.
"Does it work on a HSS tap?"
I believe it will work on anything that's iron or mild steel.
Yes, the first time I heard of this, I thought it sounded nuts.
Regards,
Joh
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Author: JMcAulay
Date: 2003-03-07 04:53
Oops, I missed a couple of BobD's questions:
"1. Since most keywork is plated with nickel or silver a brass screw would be rubbing against the plating rather than the base metal which is usually nickel silver. Right?"
Absolutely correct. Unfortunately, since it's rubbing, the plating would wear away in relatively short order, and the base metal problem would hit you. A big problem with brass-on-brass (aluminum-on-aluminum is even worse) is galling, a corrosion-driven problem that results in peeling away of surface metal, so that the pieces look as if they've been hit by a rasp. And they work together just about as smoothly, which is hardly at all. The only plating I would trust in such a situation would be fairly thick rhodium or similar metal, which should wear away very slowly.
"2. I find it hard to believe that drill rod is easier to machine than brass (or no more difficult) but let's face it I haven't made any real life comparison."
Tensile strength of the material involved is not the driving factor of how machineable a part can be. I've never machined drill rod, but my recollection is that most stainless steels can be machined faster than brass. Please don't accept this as fact without checking, as it's been almost 40 years since I ran a machine shop. (On rare occasions when things were slow in the office, I'd have one of the Master Machinists set up a small Hendy turret lathe for me, and I'd go on the floor and crank out some parts. Good for ironing out frustrations. Among the frustrations was the fact that the Journeyman Machinists made more money than I did.)
Regards,
Joh
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Author: ron b
Date: 2003-03-07 05:11
I don't mean to butt in before John's response, Gordon; rather, to additionally relay to you that my informants tell me the alum solution should be very hot but not boiling. It won't harm non-ferris metals. I haven't tried it myself yet but have been intending to - just haven't found time to assemble a setup to try it.
My informants also tell me it takes about an hour or two to dissolve the steel - four hours or so and it disappears. I suppose it would attack HSS as well as softer stuff. It might take longer, though I don't know this from experience.
And, yes, Jim, the Alum (in water) will annihilate the steel, including of course steel springs. But, then, I suppose you wouldn't have to completely dissolve the screw just to get it out.
I don't know how a hot dunk could be done if the pillars (posts) and steels are still on a plastic instrument. Maybe just a warm solution and longer immersion time -- I'm working on it... just not quite there yet since conventional methods for removing stubborn steels have worked for me.
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Author: Gordon (NZ)
Date: 2003-03-07 10:21
Thanks Ron.
Jim, I'm sure that method of staightening tubes will increase the bore diameter and make the pivot sloppy.
I support the tube (with the rod inside) between two fingers, say an inch apart, and hit the tube between the two fingers using a short rod of acrilic between the (rawhide) hammer and the metal, so as to apply the blow to the appropriate place. I determing the appropriate place beforehand by supporting the tube as above, and pressing with the thumb midway between the fingers. I try this in many locations and find out which one makes the rod move more freely (using the other hand).
This method seldom fails.
BobD: Unless an electrode is specially inserted into a hollow area such as a tube, the electroplating will intrude only a small distance inside the tube. This distance is probably negligible for small diameter tubes. This is because any charge applied to any hollow object results in no charge within that object.
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Author: BobD
Date: 2003-03-07 11:42
Thanks again to all for your suggestions and hints. Hmmm on the alum thing since: If you can't get the rod out it's still in the bushings which are in the wood or plastic. Beginner's luck I guess since I straightened the tube(which was soldered to the key) with the rod screw removed. Temporarily I've "reworked" the damaged rod and reassembled and the key works ok.
But still want to try my hand at making a new rod screw. Regarding machining: Drill rod is usually a high carbon non resulfurized steel which used to be used to make drills and probably still is used for cheap jobbers drills. Stainless is all over the map from T416 versions which are the easiest to T316 and other similar grades which are a bear. And...thanks again for the alum thing. Here I thought it was only good for stopping bleeding or making some holes smaller. Cheers
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Author: Mark P. Jasuta
Date: 2003-03-07 11:58
To find the location of a bend in a tube, incert the rod untill it binds and make a mark. Incert the rod from the other end of the tube untill it binds and make another mark. The bend is between the marks.
After you thread a new rod, using a jewlers file and an electric drill file a step where the threads stop to form a shoulder. This will prevent the screw from jamming when you tighten it. For reference, using a magnifying class, and examine another rod screw where the thread stops. Good luck, and may the force be with you.
Mark
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Author: Don Berger
Date: 2003-03-07 22:35
Doing a bit of lurking here, as I have run into the frozen/rusted rods on oldies, appreciate the info. As to alums, there are many, aluminum sulfates of sodium, potassium and ammonium with varying degrees of acidity [toward sulfuric acid]. Ammonium alum may be the most common, ? least acidic?, but have never used/thot-of it for rust removal. I've fought out frozen rods with WD40 etc, takes a while! AS to bent rods, my fav. tech mounts them in a motored-chuck, runs and uses a "holy" tool to straighten. Not sure of his tube-straightening technique, prob. same as above. Kids do drop horns, dont they!! Interesting! Don
Thanx, Mark, Don
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Author: ron b
Date: 2003-03-08 01:00
Hi, Don
Have you tried Hoppes gun oil? Just ask for Hoppes oil at your local gun and/or sporting goods store. It's an excellent penetrating oil/solvent that, in my experience, runs rings around WD40. It's a bit pricey but you can buy a little bottle and a little goes a long way.
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Author: JMcAulay
Date: 2003-03-08 01:03
In passing, I do not recall observing the use of a heated alum solution to dissolve a steel screw, rather room temp. However, it was left overnight to do the job, which was in no way finished in an hour or two.
Regards,
John
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Author: BobD
Date: 2003-03-08 14:20
Thanks again for everyone's help. Yes, I've use Hoppe's and scads of others. Straightening a rod once it's removed is relatively easy, but you can't straighten it until you get it out! My rod was straight after I got it out, it was the tube that had a bend in it that made the rod act as if it were frozen in the screw portion. Much thanks to all.
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Author: Gordon (NZ)
Date: 2003-03-08 14:39
The alum trick is a chemical reactioin. I learnt at school that every 10 degree C rise in temperature roughly doubles a the speed of a chemical reaction. There is at least some truth in it.
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Author: Mark P. Jasuta
Date: 2003-03-09 15:30
I use plain old kerosene to loosen stuck or otherwise frozen screws. It's basically my version of liquid wrench. It works well, if you don't mind the smell, and are not in a big rush. (I have "bathed" parts for over a week at times) Anyone can "rip" something apart, but, I think the objective here is to remove, to reuse.
Mark
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Author: ron b
Date: 2003-03-09 23:08
My acquaintance tells me he used the kind of alum you use to make pickles. Room temp is okay but heating it makes it work a little quicker, as Gordon already pointed out above.
I've found that kerosene works pretty well too, Mark. I don't care for the odor but that's only one (my) opinion... it'll do the job. I also agree with you that the object of any repair is to restore to as good as or better than it was when it came to you to be fixed. I wouldn't classify the alum method the same as ripping something apart though. It seems to me it would be better than drilling or grinding and certainly a method less likely to cause more damage when, for one example, a threaded hinge screw end is corroded and broken off in a post.
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