capo-hardening?

[Ed Sutton]

Mark-
I've tried burnishing the capo after dressing with file and emery paper. It
didn't do any harm, the section sounded clear, but this was just as part of
restringing, it was not a piano with zingers.
I've wondered how to test whether burnishing would produce enough work
hardening to make a difference.
Perhaps your piano would provide a test.  If you can get the strings out of
the way, an etcher's hook burnisher should fit under the capo bar with the
plate in the piano.  I suppose it's a long shot, but not hard to do.
I have a C-3 with zingers coming up in a few weeks. I hope you can give us
the answer by then!
Ed S.

----------
>From: Mark Cramer <cramer@BrandonU.CA>
>To: caut@ptg.org
>Subject: RE: capo-hardening?
>Date: Sun, Sep 23, 2001, 8:05 PM
>

> Okay, I've been to the archives and had a look.
>
> To provide background, I can tell you that this capo was dressed upon
> re-stringing. Though, as I had personally done neither, and the noise was
> bad, I removed the string and re-surfaced the capo again, this time to a
> smaller radius.
>
> If you've travelled this path before you will know the results were
> superb,... but very short-lived. :>(
>
> In reading an article, and in consultation with Paul Dempsey, I then made
> some brass shims to raise the front-duplex angle. No luck.
>
> BTW, this seems similar to the approach Ron N. advocates in the CAUT digest;
> 3/1/99.
>
> In contrast, Ron Overs, who is also mentioned in that thread, advocates
> "lowering" the string deflection angle (to 15 degrees, I believe) rather
> than raising it. He does deliberately shorten the duplex length though, and
> hardens both capo and diplex bars as well.
>
> As the zinging in this piano cannot be eliminated with front duplex muting,
> the zings re-appeared in the duration of one tuning, and the grooves along
> with them, I've decided that the capoo hardness must be the villian.
>
> Now what to do?
>
> In reading Roger's post regarding quenching the heated bar via the (moist)
> sand of the foundry, I'm wondering, with the help of my very skilled welder,
> if an "in-the-piano" procedure may be possible.
>
> Surely with all the "dare-devils" on this list, someone must've,.... anyone?
>
> Mark C.
>
>
> -----Original Message-----
> From: owner-caut@ptg.org [mailto:owner-caut@ptg.org]On Behalf Of jolly
> roger
> Sent: Saturday, September 22, 2001 12:16 AM
> To: caut@ptg.org
> Subject: Re: capo-hardening?
>
>
>
>>Based on Roger's post, I'm guessing the key is the skill of the welder, not
>>just the type of welding device used.
>>
> My metallurgy knowledge is non-existent, but I wonder about the hardness of
>>cast iron at the v-bar from normal surface cooling at the time of
>>manufacture, vs. torch-hardening and/or TIG reflowing.
>>
>>Bill Shull
>
> Hi Bill,
>             Yes there is a high level of skill happening here, It is done
> so there is barely any discoloration of the finish, and the result is just
> case hardening of the surface area.
>
> In a sand cast pour, the water in the sand acts to quench the surface, and
> case harden  the surface.  If too much shaping and filing takes place at
> the piano factory, the hardened surface may be completely removed. Just one
> of the reasons that a new piano may exhibit excessive V noise right off the
> bat.   The mere act of stringing starts to form a significant groove in the
> soft cast iron.
>
> In the foundry, if the sand box is too dry,  hardly any case hardening
> takes place, due to the absence of water.
>
> Roger
>