Adjusting a Grand Piano's Backcheck Distance

Adjusting the Backcheck Distance on a Grand Piano (Piano Tuning and Repair)

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One of the steps in regulating the action of a grand piano is to adjust the checking height of the hammers. This video walks through the process of how this adjustment should be made.

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Video Transcript:


Welcome back to the workshop of Howard Piano Industries. I'm Steve Howard of Howard Piano Industries I'm here to show you today we're going to be demonstrating with a video showing how to adjust the back check in distance on a grand piano action.

Backcheck Distance Explanation

Here we've got a model, grand piano action model which obviously, is just a model of one key in one action on a grand piano to show you a side view of what we do here when we're making the adjustments to the back checking distance. This is all part of the regulation process just one of the steps in the regulation process. We have a couple other videos on adjusting the hammer blow distance, and the left-off, and the drop and the aftertouch and key dip on them on an action.

So here you want to you want to get make sure those things are done first this is the step after that, but basically this piece right here is your backcheck and of course, here is your hammer. What happens is as you press the key I'm going to just go through really quickly. You can see the hammer goes up and then it comes back down and the tail of the hammer catches on the back check. The reason that it does that, is that it catches the hammer so it doesn't fall down. So far, if we go all the way to rest, then it's much further from the string and so the reason that it backchecks the hammer is so that the hammer first of all, doesn't just bounce, and the other reason is so that it's closer to the string if you're going to be repeating the note. So if you're doing fast repetition, repeating the same notes quickly.

It makes it more efficient that the hammer doesn't have to travel as far when it goes to play the note again. There's kind of a variation as far as how close that checking distance should be, then the checking distance is the distance from the top of the hammer to the bottom of the string.

This is this piece right here is simulating the string, so the distance when the hammer is in check and that's where it's at right there when it's when the back of the hammer is resting on the back check. That's called the checking distance and that should be anywhere typically between a 1/2 inch and 5/8 of an inch. Now I've got it adjusted right now, and you can check this with the stainless steel roll, there are gauges that you can get. But I've got it to adjust it to about a half inch right now, so again between the top of the hammer and the bottom of the string when the hammers are in check.

If you've got it closer, that's going to give you more control if you got the checking distance closer that give me give you more control when you're playing fast repetition where you're repeating the note very quickly, It gives you more control that way and then the other thing is that if you've got a little bit closer it's going to give you more control as well, so especially in soft playing. So now the way to adjust this is, first of all, you not only want it to check at the right distance but you also want the backcheck to catch the hammer at the right angle. If it's leaning too far back, it's not going to catch consistently or if it's leaning too far forward, the same kind of thing it's not going to be consistent. You want to check it a different different blow volumes. If you can, you can hit the key harder or softer.

Now that the hammer is going to check at a different checking distance depending on how hard you hit the key. So if you do but this half-inch to 5/8 inch checking distance is based on a medium soft to medium loud blow on the key okay. If you hit it much harder, it may check a little bit lower. If you do it softer it's going to be closer, so if you do it real soft, it may even have trouble checking. See if I do it right there it hits the string, but you might be able to see there that the hammer isn't actually in check. There's some things you can do if you've got too little after touch which I probably do it a little bit on this one's after touch could be slightly more on this action model as I've got it adjusted, that's going to make it so that softer playing. It's going to still be able to check on the hammer so those are a couple things to check.

Adjustment Process

Now, when adjusting the wire, you not only want to adjust it for the right angle but when you go to adjust the checking distance you're going to push it further back for the hammer you're going to push the back check further back for the hammer to check lower. If it's checking too close to the string like if it's a 3/8 of an inch you know then you've got to push the back check back a little bit further.

You can do that with your hammer you want to be careful, not to damage things but we are also here, I've got these are my factory wire blunt bending players we sell these in our store this is my favorite tool for adjusting the back checks especially the angle because what happens is, when you adjust the angle you not only have to do it up here, but you have to do it on the bottom of the back check wire as well. So you might bend it back, and then if you bend it back then you're going to have to adjust the top of the wire to get it back into the right angle okay so those are the two, but if you do is just doing a slight adjustments you can just take your finger and hold the front of the key and push back on the back check, a slight amount doesn't take very much adjustment here to make a difference in the checking distance so, So that's how to adjust the checking distance on a grand piano and again, we want that to be half inch to 5/8 inch from the string when one of the hammers in check.