Scratch tuning how too?

[Bloviator]

I'm making my first attempt at tuning on a box where most of the reeds are 6-12 cents high.

From what I read online I attempted to lower the pitch by taking the scratcher and making 3 firm scratches down towards the rivet. This had minimal effect after several tries so I went ham scratching the reed and managed to lower it from 8 cents high to 5 cents high.

I tried sharpening the scratcher to a very shallow fine point which makes a deeper cut, but does not seem to lower the pitch by any more.

Should I try sharpening it to an angle that is not as steep so it retains its point longer? Am I missing something in the videos / articles I have read? Raising the pitch has been as described.

I have seen mention of rotary tools for large pitch changes, but no mention of how you would lower the inner reed substantially.
The reeds were clearly tuned hastily with a rotary tool at the factory.

 

[Dingo40]

The reeds were clearly tuned hastily with a rotary tool at the factory

Phew!
Tuning using rotary power tools is frowned on in almost all posts in this forum !
I have seen videos where (off the block) reeds have been commercially (the reed tongue supported by a piece of steel strapping ) tuned by means of flat mill-files, also using a narrow (about 1/2"wide) emery belt sander device (sparks everywhere!), set over tuning bellows in front of a frequency meter.
Some serious amounts of metal seem to be removed!

 

[henry d]

The vibrating frequency of a given reed is affected by associated resonances in the block chamber under the reed, by the temperature, and probably by the phase of the moon. The biggest single factors though are the effective vibrating length of the toungue and the spring force of the metal the reed is made of relative to the mass that is vibrating. Increase the mass and it'll vibrate more slowly (lower pitch), lighten it and it'll go faster (higher pitch). Scratching the reed by the base means that the strength of the springiness is decreased so that the reed doesn't return from a deformation (pushed up/down) by the air as quickly- lower pitch. Scratching it up at the end removes metal makes the same spring strength more effective- faster and hence higher. in pitch. Scratching filing properly is, like most things- an acquired skill set.

You might try a quick dab of clear nail polish on the end (last 3/8 inch or so) of the reeds- it'll lower it a couple of cents and you can scrape it off with ease if it goes too low or dab on a second coat if you want more. It's really unlikely to harm anything unless you slop it around inadvertantly.

So... you can do it and there's always a first time, but go slow and know that if you bungle you can really bungle it good.

It's a question of which scratch are you focused on. If it's a box you treasure or one with substantial value I'd pony up the scratch in your wallet and get it done right. Gone awry, and that is incredibly easy to do with a Dremel, and you can ruin it beyond redemption.

"I tried sharpening the scratcher to a very shallow fine point which makes a deeper cut, but does not seem to lower the pitch by any more."
Maybe not- but reeds are thin pieces of metal which byt their nature flex back and forth and forth and back... The sharper and deeper the cut and the more likely the reed is to eventually crack at that point.

 

[debra]

When many reeds are between 6 and 12 cents high it likely means that you have an accordion that is really tuned to 442 or perhaps even 443 Hz and you are trying to get it back to 440 Hz. The best way to do that is by noting the deviations, then removing all the reeds from the blocks, perhaps all the valves too, cleaning all the excess wax off and then lower the pitch using a file. There is no more problem with inner versus outer side when the reed plates are no longer on the blocks. Then put (new) valves on, wax in place, let it dry for two weeks, then do final tuning. This whole process will take you a very long time (like over a month)...
Alternatively, when everything is still good (good wax, good valves) you can use the scratcher. Do it with the reed blocks removed from the accordion. When you have written down all the deviations you can do a first approximation using a simple rule of thumb: Every scratch on the inside reed (scratching done on the blue side of the reed) lowers the pitch by about half a cent and every scratch on the outside reed (done on the shiny side) lowers the pitch about one cent. For very low notes you need more scratches or a larger scratcher and more force, and for very high notes you need more scratches with a smaller scratcher, very sharp, and with very little force. Piccolo reeds get very fine scratches, and I then make a first guess that every inside scratch does 0.1 cent and every outside scratch does 0.2 cents.
If you are scratching at say A4 and your scratches achieve much less effect than what I guessed (0.5 cent inside, 1 cent outside) then either your scratcher isn't good or you use too little force. If it achieves much more effect then you are using too much force.
Also note that scratches should start about half-way towards the rivet. If they start further towards the tip of the reed they will have only one effect and that is to weaken the reed, without altering the pitch by much. (The part of the scratch closer to the tip raises the pitch and the part of the scratch closer to the rivet lowers the pitch and so the whole scratch does nothing.)
Tuning is really a difficult skill. There are courses in accordion repair and tuning for a reason: to teach you the right way to do things.

 

[tcabot]

Please do no use rotary power tools - too many reeds absolutely butchered by ham-fisted tuners.

Unless it's a spot-tuning job for a cent or two, I recommend using sandpaper and sanding by hand across the whole width of the reed. 180-240 grit does just fine. Scratching a few cents off will likely damage the reed by making huge deep grooves in it (12 cents - that's at least 12 deep scratches in a reed that's only about 0.4mm thick to begin with). Sanding is easy, almost failsafe and it's pretty much the same process as what's done to the reed when it's being made.

You can try using a hand file instead of sandpaper, but it can be very tricky once the reeds are already mounted on the plate and the valves are glued on. You can make more of a pig's ear out of the job compared to sanding. Filing is only easy before you rivet the reed onto the plate imho.
For inside reeds, if you're not de-waxing the reed (you should really consider that if you're taking off more than 5 cents, as it will make your life easier) then you can shape some wooden ice-cream sticks and glue small strips of sandpaper to the edge, then use then to reach under the valve into the slot.

I'd say tuning is a very easy, but extremely, extremely, extremely time-consuming skill, and the amount of time required to tune a block of reeds grows exponentially, the less skill you've got.

 

[colinm]

I'm making my first attempt at tuning on a box where most of the reeds are 6-12 cents high.

From what I read online I attempted to lower the pitch by taking the scratcher and making 3 firm scratches down towards the rivet. This had minimal effect after several tries so I went ham scratching the reed and managed to lower it from 8 cents high to 5 cents high.

I tried sharpening the scratcher to a very shallow fine point which makes a deeper cut, but does not seem to lower the pitch by any more.

Should I try sharpening it to an angle that is not as steep so it retains its point longer? Am I missing something in the videos / articles I have read? Raising the pitch has been as described.

I have seen mention of rotary tools for large pitch changes, but no mention of how you would lower the inner reed substantially.
The reeds were clearly tuned hastily with a rotary tool at the factory.

Are you sure you are scratching the reed you are tuning?

 

[debra]

Are you sure you are scratching the reed you are tuning?

It's a mistake that happens to the best!
(Has happened to me, even though I'm not the best...)

 

[Bloviator]

Are you sure you are scratching the reed you are tuning?

I was not. So I taped everything but what I was trying, then I was sure.

Thanks all for the tips. The accordion is supposed to be tuned to 440 hz. It is just the cheap(ish) Chinese accordion that I purchased to learn on.
Now that I have a larger instrument I wanted to tune it as that was my major complaint. I actually enjoy the instrument for folk music and when playing in a trad session it makes little difference if you are tragically out of tune.
The tuning varies significantly, just happens that the first row / block happens to be mostly high, there are a few that were flat and they were easily raised. Having much more difficulty with the lowering.

I'm not going to remove the reeds from the block because my primary goal was to learn to spot tune.

From reading responses I think my next attempt this weekend will be to file the scraper to a less steep point and apply more pressure per scrape.

 

[debra]

From reading responses I think my next attempt this weekend will be to file the scraper to a less steep point and apply more pressure per scrape.

That's a really bad idea. A scratcher always needs to be very sharp. For larger reeds there are scratchers with a flat end and these also need to be sharpened to keep the edge at the end sharp because it's with that edge you do the scratching.
I mostly use a pointy scratcher and need to sharpen briefly after every few reeds (on a diamond-coated stone).

 

[Bloviator]

That's a really bad idea. A scratcher always needs to be very sharp. For larger reeds there are scratchers with a flat end and these also need to be sharpened to keep the edge at the end sharp because it's with that edge you do the scratching.
I mostly use a pointy scratcher and need to sharpen briefly after every few reeds (on a diamond-coated stone).

I'm not sure I understand why a less steep angle an the scratcher would be different than a larger scraper.

 

[debra]

I'm not sure I understand why a less steep angle an the scratcher would be different than a larger scraper.

The less steep angle while scratching means less pressure on the reed (and thus less risk of bending the reed out of shape). For a scratcher to work at a less steep angle it needs to be really sharp.
When you are just starting out with tuning you should always take out the reed block so that you have more room to work, and you can support the inside reed better from below. The idea of "in situ" tuning also only really works for reeds that are large enough to have valves. The smaller high-pitched reeds are too delicate. You cannot safely pull the inside reed up as you will bend it out of shape. And the piccolo reeds that are upside down can only be safely tuned with the reed blocks removed from the accordion. The "better safe than sorry" motto always applies.