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Out of round bell ring

18 Nov 2009 10:56 #345 by Gregory Beckwith
Out of round bell ring was created by Gregory Beckwith

Dear Mr. Beckwith,

My girlfriend has a Holton 179 with a detachable bell. Unfortunately the ring is very hard to screw on due to non visible damage to the Male ring of the screw bell. There may be slight (miniscule) ovaling to the male bell ring area. What would be the best way to repair this and does a typical repairs person have the tools to "re-round" a holton threaded screw bell? Would it be best to consult a machine shop?

On another note: What is the job outlook for instrument repair technicians? How does obtaining an instrument repair degree further market musicians in an unsteady economic climate?

Thank you for your help; you do WONDERFUL work!


Greg Beckwith's Answer:

Hello and Thanks for your questions.

Job outlook for instrument repair technicians:

The job outlook for instrument repair technicians remains good. All our graduates last year that were looking for employment secured full time positions. In addition instrument repair shops/employers we are in contact with indicate they have steady business- the sources and instruments may be changing but they are staying busy. Having a skill that is employable and needed by musicians, school districts and teachers is highly advantageous for anyone, let alone a musician to provide additional income.

The competition that exists with funding for arts organizations with all other entertainment choices means dwindling dollars and less calls to perform if one is relying primarily on those sources for income. Having a skill in any area, not exclusively instrument repair helps provide additional avenues for income and opportunities for employment. There are many repair technicians that perform on the side but count on the steadiness of their repair job for their primary source of income.

I am still a performer and it’s common that I return home after the concert with an instrument to repair- and that’s without asking! Once you establish yourself and are “seen”, folks will find you. It’s very rewarding and satisfying to repair and keep instruments functioning to their best potential- especially when they sit and are performing right next to you!

Detachable screw bell flare issue:

An experienced technician in a repair shop can deal with out of round rings and truing threads. So the following can be passed along to the repair technician of choice. An owner of the instrument in question would be somewhat at risk attempting the following without prior experience manipulating brass, thread repair/truing and working with miss-aligned parts; all areas that an experienced technician is familiar with and can troubleshoot when/if problems arise.

    Do the rings start “square” to each other when threading on?”
    Is it cross-threaded?
    Are the threads in good condition?
Many times a thread file can help true the threads if they are the issue A repair technician can also use a triangular solder scraper carefully to true a poor thread.

Once the above is determined or corrected look at roundness of the ring:

A good way to pinpoint the area or determine if it is out of round, is by painting the bottom edge of the male ring with a permanent marker or similar. Place the marked ring on a clean white piece of paper and make an imprint of the ring. This is a means to see and mark where it is out of shape. Do it several times and mark the bell somewhere visible on the outside for where it appears- not round.

Qualifier- severely out of round rings can only be brought back completely, many times, by either heating to relieve stress or replacement. It should be stated to the customer that the rings' operation can probably improve to a better condition but not to a "like new" unless extensive and costly repairs ensue. If a ring is dented or has a flat spot- this requires something more extensive than only making it round and would be a case by case repair depending on severity.

Dealing with out of round

The next steps are best performed by someone with experience, but even a seasoned technician who has not performed this should be fine as they proceed slowly, are patient, and observe the process carefully.

The ring can be brought back to round by a few methods. (Once again- be sure when checking the threads that they start true and are not cross threaded)
    1st- By tapping with a very soft mallet (rubber best- a brass technician should have one available for doing bell rim repairs) With this technique they tap where it is out of round (usually oval appearing-so tapping would occur on the high sides of the ring) and carefully bring it back to round. Check with the marker as described previously and try the ring periodically with the matching female side of the bell body.
    2nd- If the out of roundness is barely perceptible, warming the area while the parts are assembled can help to "true" the male side. Care should be taken to only heat the parts -no unsoldering should occur with this attempt. Heating of the male side apart from being assembled to the female side may help also if the rings cannot be assembled.
    3rd- This takes the most care and skill and attention. If there is definite perceptible oval and tapping is a concern for harming the ring, or is not successful, the following is the next best approach.
Find equal thickness of soft material-leather, cardboard, felt. They are going to be supports on either the side of the ring on a table and will be placed where the ring is oval (each piece contacts a small portion of the circumference of the entire ring). The pieces are placed under the male ring on the table on each side of where it shows being oval as below (what is shown below is the ring with an oval and the pieces underneath each side where it would attach to the female ring; the oval ring is depicted-rectangles are padding that extends under the rim.
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The next step is to place hands on both sides of the bell rim, thumbs bent slightly to the inside of the flare (the arcs and X’s in diagram, and above the pieces of padding) and lightly flex outward-both hands, both sides- with a springing action on the bell rim. This will cause the oval to move toward round. One can Watch the interior hole of the ring until it appears round while flexing. The bell/ring can be rotated to different points on the padding as it becomes apparent where the out of roundness is located. This can be done and then checked with the female side a few times. (Technicians should know that a rim affects the roundness of a throat and in this technique they are taking advantage of that aspect to adjust the roundness of the screw-ring). Also- moving the part to its “true” position may require moving the metal beyond that point and allowing it to relax back (common scenario when working with brass alloy metals). Care should be taken when flexing the rim to pay attention to the amount of flexing on it, which should be obvious, to avoid bending over the sides and folding it.

These are the steps and techniques that have been used with success to round-out the male side threaded ring of a detachable bell. As mentioned earlier, the last resort is to replace the ring. It requires precise placement of the new male ring. Careful soldering done in stages to prevent parts from getting soldered together is necessary.

This last step is optional but helpful. Determine where the rings “start” to thread together. Screw the parts on and off several times and as they are being unthreaded observe where the rings release from one another. Be sure to support both parts and have a soft landing just in case the bell releases and slips out of hand. Mark the spot at the moment the male/flare side releases from the female/body side with a sharpie marker on both rings with a line or a dot that matches up the sides for a visual reference when they are apart. This will show where to start threading the bell parts together by matching the line or dot mark and is helpful for the owner to get the correct position each time they assemble the bell. Some manufacturers will do this more permanently with a scribe mark. It’s also good for the threads to maintain the “lead” thread and prevent cross threading each time it is assembled. I will do this for screw bell conversions so the owner has a reference point and starts the thread accurately as they become comfortable threading on a detachable bell.

MN State College SE Technical- Red Wing, MN
Greg Beckwith- Instrument Repair Instructor

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