Can a crack in a brass PF cup be repaired?

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Postby erdnasephile » 01/04/13 12:51 PM

I was talking cups with another forum member, so I thought I'd run this question by all of you.

I own a set of brass PF cups made by Busby (circa early 1980's).

One of the cups has developed a 1 cm vertical crack that is visible at the base of the cup on the outside. It runs from the rolled lip to the lower ring. I can feel the crack as I run my fingernail over it.

Can such crack be repaired?

If not, can it be covered well by having the cups plated? If so, what plating would you suggest? (Chrome? Nickel?)

Thanks in advance for your help!
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Postby Jim Martin » 01/04/13 01:12 PM

"Paging Dr. James Riser.

Dr. Riser, please report to the Active Topics Forum."
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Postby Dave V » 01/04/13 01:20 PM

Plating won't cover up any flaws. In fact, it might even emphasize them.

Pending Mr. Riser's reply, I've seen brass musical instruments that have looked like they were run over by a truck restored to near original condition. A good instrument repair shop might be your best bet. They can solder the crack (not lead solder, but the right color of high temperature solder to blend in) and then repolish the cup to hide the repair work. The rolled bead might be an issue, but they should be able to tell you better than I what can, or can't be done.
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Postby Jim Martin » 01/04/13 01:43 PM

You're correct about brass instruments, Dave.

There is an amazing brass repairman here in St. Louis who does historical restorations on brass musical instruments - flawless.
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Postby Tom Gilbert » 01/04/13 02:24 PM

What Dave and Jim said.
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Postby erdnasephile » 01/04/13 03:35 PM

Thanks for the replies, guys--appreciate it. I'll see if a serivce like this exists where I live.

Pending Dr. Riser's diagnosis, here's a picture

Image

Is this a natural thing to happen to brass cups over time or is it a particular characteristic of the Busby cups?
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Postby Dave V » 01/04/13 04:37 PM

It's likely a stress fracture from insufficient annealing during the spinning process. I hear brass is more brittle than copper and can be prone to cracking.

If you lived in the Tulsa, OK area I'd point you to my brother Mark who works magic with broken instruments.

http://www.palenmusic.com/t-band_repair.aspx
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Postby Jim Riser » 01/04/13 08:29 PM

Riser reporting in ...
And here we have an example of why I never make any brass cups. Brass requires multiple annealings during the spinning process. The last step of rolling the bead introduces unwanted stresses at the mouth of a cup. Annealing the cup after spinning the bead would take care of the stress problem but make the cup much softer and easily subject to denting.

Most brass spinnings end up with such splits. This includes antique auto headlamps, Paul Fox Candy Bowls, brass cups, lamp bases, etc. If it is brass, spun, and has a rolled lip, it will most likely develop such splits.

In addition to splitting, the spinnings usually have been thinned out during the spinning process as the mouth was approached. This compounds the problem.

Your best bet is a good instrument repair person using the correct filler metal. Depending on the situation, the metal might be soldered with the appropriate solder or tig welded with brass filler rod. Soldering will soften the metal. It can not be rehardened.

I ran across the perfect tool for the task but I do not have a spare $7500 to buy it.

Stick with a good instrument repair person or turn the split towards the wall.
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Postby erdnasephile » 01/04/13 10:27 PM

Many thanks, Mr. Riser (and everyone else on the thread). I very much appreciate your time and expertise.

A couple of questions please: are the CNC brass cups less likely to develop these splits?

Also, would higher quality spun cups like the brass Sherwood cups also be at risk for splits?
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Postby Tom Gilbert » 01/04/13 11:33 PM

What I took away from Jim Riser's reply is that it's a brass thing. Copper must be easier to deal with. But then again Jim
should answer that, not sure if the Sherwoods are immune or not.
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Postby Jim Riser » 01/05/13 01:00 AM

CNC cups are machined from a solid brass bar. This process cuts away metal and does not introduce the stresses leading to the rim splits. In addition, the process dictates the necessity for much thicker walls.

Copper is a much friendlier metal than brass for spinning. A careful spinner will try to keep the cup wall thickness as thick as possible but metals tend to thin the farther the spinning progresses. This can be countered with technique but not completely. The Busby cups were most likely leftovers from Danny Dew. Busby never could find a good spinner willing to work with him. These old cups started out rather thin and only got thinner by Danny's spinners. I have seen examples of the cups Busby tried to have spun. The top of half of the cups was paper thin with big splits.

Thicker cups tend to resist splitting better but may not eliminate it. On brass and stainless steel these splits may not appear for decades.

Brett has his cups spun and engraved for him. He and I have discussed a number of things regarding cups but I have not discussed the techniques Brett's spinners use with him. Since many of Brett's cups are engraved or otherwise decorated (repousse, stamping, and chasing), they may well be annealed (resoftened to remove stresses induced by spinning) by his spinners or decorators. You will have to ask Brett. I would be very surprised if Brett's cups were not annealed as the decorating is not usually done on anything but softened metal. Brett's cups are much thicker than the old PF cups and even annealed metal would be resistant to denting. Brett offers a good product.
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Postby Jim Riser » 01/05/13 01:37 AM

If you would like to see the process I used to make an extremely thick set of cups:

http://db.tt/2kRsiALi

Enjoy.
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Postby Jim Martin » 01/05/13 02:22 AM

Thanks for the 'thick cup set' post, Jim, as well as all of the insights.

What an amazing, artistic piece of craftsmanship!
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Postby erdnasephile » 01/05/13 03:18 PM

WOW! I love looking at the skill and art that goes into your cups, Mr. Riser. Thanks for sharing that with us!

I'll also take your suggestions and try to find an instrument repair person around here. (If I do get the cup repaired, I'll post a picture at some point)

I'll also run the brass split questions by Brett Sherwood.

Thanks, everybody!
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Postby Jim Riser » 01/06/13 01:51 AM

Guys,
I have received a number of emails asking about such a repair job. The biggest problem is that the cup metal where the splits occur is very thin. When such metal is heated for high temp soldering, it can literally melt away.

The bells of brass musical instruments are not made the same way as cups. See:

http://i348.photobucket.com/albums/q345/qcm1954/K11.jpg
http://i348.photobucket.com/albums/q345/qcm1954/K10.jpg

These images show how the instrument bell is formed from folded over brass and a separate disc for the flare. This technique keeps constant metal thickness which is important in an instrument. Instruments have a thick steel wire spun in to the bead of the bell to help prevent dents. Cups do not. The thicker metal on instruments makes repairs possible. The old PF cups may be too thin near the mouth for repairs. The instrument bells are hand hammered to shape, tabs cut along the seam, soldered, then spun to final shape. Everything is geared towards constant metal thickness for perfect tone.

Hopefully this will help to explain why the cup may not be able to be repaired. It is all about stresses in very thin metal.
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Postby Kent Gunn » 01/06/13 11:13 AM

I really enjoyed reading the pdf and looking at the explanatory pix on making the monster-thick cups.

Thanks,
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Postby erdnasephile » 01/07/13 08:42 PM

Update:

I took the cup to a well-regarded instrument repair company here in town. The owner seemed to know what he was talking about and was rather intrigued about possibly repairing a magic prop.

However, after examining the cup, he found another split I hadn't detected before. :(

He said that while he believed he could repair the splits, I would still be left with a visible line where each repair would be. He was also concerned that this would stand out when compared to the other two cups. In short, as much as he would love to repair the cup, he recommended against it.

Bottom line: I've decided not to attempt a repair (especially now that there is a second split in the cup). Curse you, Jeff Busby! :mad: (To be fair, the cups are 20+ years old, and are certainly still perfectly functional. Yes, I know, it's what you do with the cups, not the cups themselves that matter. Still...).

So, perhaps it is time for a new set of cups? I did contact Brett Sherwood upon Mr. Riser's suggestion. Mr. Sherwood says that his brass cups are properly annealed and are thick walled so they are less susceptible to cracking.

I really like the golden look of brass, but don't know if I'm willing to risk spun brass again.

Alternatively, I could learn to love copper, especially if the smooth copper Sherwoods are in view. (Is copper as dent resistant as brass?).
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Postby Richard Kaufman » 01/07/13 10:29 PM

Joe Porper has some sets of his cups still available and they're very very nice, particularly if you like a heavy cup.
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Postby Jim Riser » 01/08/13 12:32 AM

Joe's cups are all machined - no induced stresses and hence no worry about splits. Plus Joe's cups are nice! This is a good option.
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Postby erdnasephile » 01/08/13 01:15 PM

What is your opinion of the CNC Johnson Cups v. the Sherwood Cups (smooth brass) v. Joe Porper's in terms of build quality and suitability for performance? (I intend to actually perform with the cups--not for shelf sitting. I know ultimately the choice will come down to personal preference, but I would certainly value y'alls opinion nevertheless).

Thanks!
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Postby erdnasephile » 01/08/13 01:16 PM

To: LH
Thanks for the PM: I could not reply because the forum says you have reached your PM limit. Please let me know when you've cleared out a few messages, and I'll reply. Thanks!
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Postby Jim Riser » 01/08/13 02:09 PM

erdnasephile wrote:What is your opinion of the CNC Johnson Cups v. the Sherwood Cups (smooth brass) v. Joe Porper's in terms of build quality and suitability for performance? (I intend to actually perform with the cups--not for shelf sitting. I know ultimately the choice will come down to personal preference, but I would certainly value y'alls opinion nevertheless).

Thanks!



I feel that all are well made and durable. I would have liked the Johnson to be a tad larger or a tad smaller. The size is my only concern. With those cups any would be fine for performances. The Porper and Johnson would be tougher due to metal thickness.

You could not go wring with any of these.
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Postby Jim Riser » 01/19/13 03:59 PM

Now would be a great time to pick up a set of Porper Brass Cups. See Joe's ad in the current issue of Genii. This is a great deal!
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Postby erdnasephile » 01/20/13 12:58 AM

Jim:

Thanks for thinking of me...

It just so happens that I had decided to make the Johnson cups my performing cups (I even acquired the extra chop cup to make a combo cup set just in case).

I was paging through iGenii when I spotted the ad 3 days ago.

I found the box from Joe Porper waiting for me at home today...

Wow! Just WOW!

They are everything you said and more: incredible, precision workmanship, nice and heavy, no wobble in the stack, and they handle like a dream!

Can't wait to start practicing so I can eventually get these beauties in front of an audience! :grin:

(Just need to find a bag for them)

Thanks again for all of the advice and recommendations!
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Postby Jonathan Pendragon » 01/21/13 07:30 AM

I perform with a set of Sherwood brass cups and I love them. I have owned PF and Johnson cups, both excellent cups. Cups become a very personal piece of magical apparatus. I like the larger final load load capability, lower profile, nested weight and general appearance of the Sherwood cups, but mostly I like the way they feel in my hands and that, I believe, is what eventually determines a good choice. I would also like to add that Brett Sherwood was very helpful when I retro fitted (chopped) one of the cups in my set by sending me two different "strength" balls to experiment with.
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Postby Terry » 01/21/13 12:17 PM

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Postby erdnasephile » 01/21/13 04:41 PM

Many thanks! (Another GF member had great things to say about those bags as well)
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Postby Joe Naud » 01/21/13 06:06 PM

Another thing that works great and is quite a bit more protective are camera lens cases. If you can find the right size they work great.
Peace, Joe
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Postby erdnasephile » 01/21/13 10:14 PM

Hi, Joe:

That's a great idea--thanks!
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Postby Jim Riser » 01/23/13 10:27 PM

OK, guys;

Here are two brass cups which will never split:

http://jamesriser.com/Magic/CustomBrass/Cup.html

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Postby erdnasephile » 01/24/13 12:04 AM

Very cool!
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