PA white key edges. Chamfer - functional?

[TomBR]

I seem to remember reading, possibly in George Bahich's book, that the chamfered sides to the white keys on more modern piano accordions are functional, presumably helping to keep the fingers centered on the keys, and to reduce "mis-hits!"

(I assume "chamfer" is a normal word, but as a lifelong woodworker I'm wondering. Where the sharp corner is taken off a right angled edge so that it's slightly rounded or has a tiny bit at 45 degrees. Like a rounded edge but very small.)

I've only ever played old accordions with very flat white key tops and minimal chamfer so I'd be interested in views on this.

I'm refurbishing an old box, and with the treble action disassembled it's easy to see how the white key tops have been cut out and a very small chamfer done by hand. It's not an instrument of historical significance, and the keys need a good clean so I was thinking of increasing the chamfer while I'm at it.

I'd be interested if anyone would kindly measure the approximate width of the "valley" near the ends of the keys of their beautiful modern accordion! That would include both the gap between the keys and the chamfer on the keys on both sides.

Cheers!
Tom

 

[JIM D.]

Accordions made in the 20's to the 30's had keyboards with waterfall keys and sharp edges as a norm. Rarely Glissando's where used with these keyboards as the sharp edges were capable of taking the skin off your fingers. In the 40's more and more accordionist's started custom ordering accordion's with a chamfered key top and the industry as a whole made a chamfered key top a standard. As you may know key tops and Chamfers will vary from different firms and their makes and models. When replacing key tops on a customers accordion in 1/2 these cases the key tops will have to be re-trimmed and re-chamfered. I have many student and pro model accordions in my shop at any one time and I have the customer try various keyboards and decide on the feel they prefer. If you have or played a box with a keyboard that you prefer, measure the chamfer and go for it. I use an adjustable router table to cut the chamfer and then buff to a polish.

 

[TomBR]

Thanks Jim, that's very interesting and helpful. I don't have any other instrument to try, and in any case I'm limited by the thickness of the plastic top of the wooden keys so I'll just have to do what I can, but it's encouraging to know that this is a "known adjustment."

If you're using a rounding-over bit in the router table what sort of radius?
Tom

 

[JIM D.]

I have old round over bits that I've gathered for years now. The old bits were formally used for trimming laminate counter tops and still hold an edge as I'm only cutting plastic. I use a piece of old stock, vary the bits, and adjust the table until I get the bevel I'm looking for. The Buffing wheel also has an effect on the key top bevel overall.

 

[Soulsaver]

Chamfer gap chamfer (cgc) Mine seem to be cgc between 4 and 5mm - Gap variability and difficult to be precise with chamfer edge is probably responsible for the tolerance. 1970s Hohners cgc is smaller at 2mm but the keys feel slightly more domed/beveled than my Italians.

 

[TomBR]

Thank you both for the info.
Tom

 

[kimric]

I have done this to a couple of old instruments, though I sometimes call it a bevel.
I used a large new file for metal and just ran it down the corner (keep the file moving ,don't file in one spot) until I liked the look of it took only a couple of min a key. You can then hit it with 1500 -2000 grit wet sand paper and then the buffing wheel, you can give them a nice polish at the same time.
I think you started to see more doming when the keys started to be molded as it was easy to build that in to the design.