 The Clarinet BBoard
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Author: Mark P. Jasuta
Date: 2003-07-11 19:27
Hi all,
I am seeking opinions on a repair method. On a lower joint pinky key, I had a pivot that rattled from side to side (perpendicular to its axis). It didn't really cause a problem other than making more noise than I would allow. I inserted some thin plumbers Teflon tape into the pivot hole in the key, drove the screw in and the problem was gone. (I tried this after an unsuccessful search for another screw.) It can easily be removed with a pin if need be. Because it is "soft Teflon" it will form itself to any shape, not fall out or harm the metal, is not harmed by lubricants, and really quiets the keywork down. Has anyone done something like this?
Best Regards
Mark
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Author: BobD
Date: 2003-07-11 20:02
Interesting,Mark. I recently acquired a LeBlanc Infinite and in the process of checking it out discovered that in at least one of the lower rod tubes was a "nylon" bushing . I haven't gotten around to checking the others yet. I say it is nylon but it could be some other white plastic....might even be teflon filled nylon. In any event it looks like the plastic that is used for some A/G# adjustment screws. I've only used plumbers teflon for temp.tenon cork repair so far.
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Author: Mark Pinner
Date: 2003-07-11 23:54
The post needs putting back in the right place or the keywork needs swedging. Teflon tape, VCR washers may provide a temporary fix. You should get it done properly before the pivot screw or key tube gets damaged. The pivot screw is made of harder material than the keywork. If the hole in the end of the keytube is not as centred as possible with the pivot screw the whole will over time become bigger from wear and the problem will get worse. It sounds like you are talking about the LH F/C assembly where this problem occurs commonly especially on plastic Yamahas.
Teflon has its uses but this is not one of them.
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Author: Gordon (NZ)
Date: 2003-07-12 06:30
And if it is the E/B key, slopping around at the pivot definitely affects the reliability of the two pads closing together with correct alignment to seal well.
Teflon tape is so 'squishy' that it will quickly become deformed until you once again have metal-to-metal contact and sloppiness.
We are talking about bearing surfaces here, and teflon tape is definitely not a bearing material. Even when SOLID teflon is used as a bearing material, such as on the top of pillars supporting motorway bridges, to allow smooth movement with thermal expansion of the bridge, the solid blocks must be contained to stop the stuff oozing out.
Teflon tape is a sealing material. Hence, it may make the sloppiness quieter, but is hardly likely to reduce the sloppiness much after a few hours of playing.
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Author: David Spiegelthal ★2017
Date: 2003-07-14 15:16
In industry Teflon (or more correctly PTFE) is usually avoided as a bearing material because it cold-flows ---- that is, it extrudes itself (deforms/squishes/oozes out) over time under even slight load. Teflon tape, as pointed out above, works only for the very short term. A somewhat better material would be nylon, a much better material would be Delrin (my apologies to DuPont for using their trade names, which however have become so commonly used that most people don't even realize they're trade names).
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Author: Mark Charette
Date: 2003-07-14 15:29
David Spiegelthal wrote:
> In industry Teflon (or more correctly PTFE) is usually avoided
> as a bearing material because it cold-flows ---- that is, it
> extrudes itself (deforms/squishes/oozes out) over time under
> even slight load.
While I know that's true (having used a lot of teflon gasketing while in the US Navy and watching it flow under moderate force - why we used it for gasketing!), there must be something more to it. Dobsonian telescopes have used pure PTFE for bearings for quite a long time, and they're quite heavily loaded (ever pick up a 24" telescope mirror?). They use charts for the lbs/sq in so that they don't get the problem. The bearing is a sliding one, normally PTFE on Formica (with the pebbly Black Start Wilsonart the preferred Formica-like material) with very well controlled frictional properties.
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Author: David Spiegelthal ★2017
Date: 2003-07-14 18:14
Mark, I'm surprised to hear about the Teflon telescope bearings --- how long do they last, and must they be maintained fairly cool? Cold-flow (low-temperature creep) generally increases in rate exponentially with temperature and somewhat more linearly with load, so perhaps the makers of the bearing have found a combination of relatively low loading pressure and benign upper temperature environment that brings gradual deformation of the bearing down to an acceptably low rate. Are the edges of the Teflon contained by a lip or suchlike that might make it more difficult for the material to extrude? (I guess this is getting a bit off-topic, eh GBK?)
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Author: GBK
Date: 2003-07-14 18:22
>I guess this is getting a bit off-topic, eh GBK?
![[huh]](http://test.woodwind.org/clarinet/BBoard/smileys/smilie11.gif) Can't tell ... your recent teflon dissertation still has me lost ...GBK
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Author: jim lande
Date: 2003-07-14 20:07
This is another reason why I am a C quality amateur, compared with some of the A quality pro techs who post to this board. I use teflon tape to quiet keywork. It does tend to flow out over time. So I wad in some more. I have been tempted to buy swedging pliers. Then again, every tool in the catalog looks like it might be useful sooner or later, and this one looks like it takes some skill. Since I only work on a couple horns each year, and since my playing (a few hours per week) gets spread over many horns, I guess the teflon is good enough. And maybe it will be good enough for Mark, too. Certainly, it is better than nothing
People ask the difference between the $200 plus rebuild and the $100 rebuild. I imagine that swedging vs wadding teflon vs ignoring the noise/slop in pad fit is one example.
However, since we digress, I had a friend who wanted a big telescope. He was dying of cancer, so I subscribed to Sky & Telescope and the two of us pored over articals and discussed what type of scope he wanted, etc. (Even then, my eyes were bad enough that I could barely tell if I was looking at the moon or a street light.) Anyway, I was sent to San Francisco on business and ran into the Sidewalk Astronmers club. I looked at the big cannon-like telescope and (in an attempt ot show off my new knowledge) observed that it looked like a Dobsonian telescope. One of the men looked up and said "Yes. I'm Jim Dobson. Glad to meet you." WOW!
Anyway, they had the scope trained on one of the craters of the moon, approximately tangent to our line of sight. In other words, you could see outer space over the edge of the crater. He then asked if I saw occasional glints of light. Indeed I did and I couldn't figure the color. Dobson explained that glass beads formed when the asteroid (or whatever) crashed into the moon to form the crater. (Silica vaporized and then cooled as it fell.) Since there was no atmosphere, many of the beads were still on the surface, refracting light from the sun. Thus, those little sparkles came from glass beads less than 1/4th inch across, sitting on the moon. That was absolutely mind blowing.
I did have my clarinet with me, but did not play for the occasion.
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Author: Don Berger
Date: 2003-07-14 20:10
If more is allowed, GBK, while I'm not much knowledgable about the polyfluoro[halo]ethylene family, there are many "grades" as in the poly[and copoly]olefin family with differing molecular weights and therefore differing cold-flow etc character. So, IMHO, one can choose which polymer will be suited to the application! The more-common varieties may not be suitable !! Don
Thanx, Mark, Don
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Author: Mark Pinner
Date: 2003-07-14 22:03
I think it is probably better to actually fix the problem. It is not a difficult job to re-set a post if this is the problem. Likewise if it is necessary or on fact possible to swedge the key tubeit shouldn't cost US$200. If we are dealing with a dodgy old instrument of no value then don't bother. If the horn is a quality instrument. You would not, or shouldn't, drive your car with defective wheel bearings. The same principle applies.
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Author: Synonymous Botch
Date: 2003-07-14 23:17
A twenty-four inch Dob!?
Somebody has apeture madness...
Must be securely mounted...
I wonder if the Teflon bearing is a sandwich of the slippery stuff layered to the heavier substrate?
Teflon sheets are being sold at repair outlets like J.L. Smith & Co.
It maybe that these are a higher Molecular weight sintered or impregnated with PTFE...
*****
In any case, swedging a key to fit is a quick (and nearly permanent) fix.
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Author: Gordon (NZ)
Date: 2003-07-15 04:44
Kraus says that the glueable sheets he sells are sintered.
It does not look very flowable, but if I bite it, it certainly crushes (= extrudes)easily, which is why I don't use it where a load is very concentrated, e.g. betweeen F/C key and lever. I sometimes use it, laminated to thin composite cork, in the linkage from G# lever to key on a sax, to reduce friction. It is poor as a linkage silencer - hence the lamination.
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Author: Mark P. Jasuta
Date: 2003-07-15 16:31
I'm back,
I may have been misunderstood on my use of Teflon tape. First the key fits perfectly between the posts. The problem solved with the tape was that it seemed that the point of the pivot screw was to small in diameter, or the hole on the end of the key was too big. A very small piece was put into the hole at the end of the key to solve the problem. The process for the most part formed a Teflon bearing inside the end of the key. I would never use it for "end play between posts" because it is too soft for long term use in this location.
Best Regards
Mark
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Author: Gordon (NZ)
Date: 2003-07-16 05:19
Which key?
As I wrote before, I would regard it as too insecure in its location of the point screw in the hole in the key if it were the E/B key, because precise, reliable closing of the E/B and F/C pads depends on this key's pivoting being secure. Quiet but still squishy does not equal secure.
Likewise the A/D key for reliable 1-1 fingering of Bb and secure closing of the right hand ring key pad.
Other point pivots are not so critical.
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Author: Mark P. Jasuta
Date: 2003-07-16 14:06
Gordon,
Its the key that controls the lowest pad on the lower joint (E pinky key). The "play" was located in the key touch end (opposite the pad). Play was about 1/1000 in. maybe a little less.
Best Regards
Mark
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Author: Gordon (NZ)
Date: 2003-07-16 22:00
Yes, what I call the E/B key.
I actually think your idea has some merit as a fix without adjusting the pivot screw further into the post, which always concerns me a little because that is a destructive process.
However I would want to be sure that it reliably positioned the key on point screw, during considerable future playing, before I used it on customers instruments.
A related approach would be to smear the pivot screw and threads grease, clean the hole in the rod very well, and assemble with a drop of superglue in this hole, with the aim of creating a superglue bush in the hole. It is probably a high-risk operation until refined. I've used a similar approach to bush a stack key post on a sax, very quick and successful.
I certainly would not recommend that every body tries this! If the superglue DOES get into the threads, then the post would need to be heated to extract the screw, and the thread posible cleaned up with tap and die.
Perhaps instead of grease, just put some cling film between the post and the key, so that when the screw is put in, the cling film seals the superglue out away from the thread and post.
I take no responsibility for the results if anybody tries these approaches. The potential for a big mess and damage is significant.
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Author: BobD
Date: 2003-07-16 23:05
I always enjoy Gordon's in-depth analyses and ideas.
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Author: Mark P. Jasuta
Date: 2003-07-17 02:42
Gordon,
You are correct. I wanted a way to take up the slop without sinking the screw further into the pivot hole. Another idea I am toying with is to get a spare screw and coat the point with silver solder, then machine it down to the size and length I need. What do you think?
Best Regards
Mark
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Author: Gordon (NZ)
Date: 2003-07-17 06:21
I think that is wonderful. I have made pivot screws in the past, and know that getting the point end right to fit a post & key with no modification to these is high precision stuff for trial and error machining, and hence time consuming.
I guess you have plenty time! Shall we take bets on how many times you need to re-do the silver-solder?
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