Piano World Home Page Forums Our Most Popular Forums Piano Tuner-Technicians Forum Piano technician in Denver, CO area to fix Kawai grand

That too, the force from below acting on a lever provided by the (quite wide) head. Possibly also a sideways component, at least on the one with the obvious wear; the edge of the head pushing against the rim putting a lateral force on the screw.

The question of seller's and manufacturer's liability came up the other day on the UK site, and this thread was a case in point. Brand reputation also comes into the picture. I'd say the fine folk at Kawai should have a good look at the photographs, especially the production engineers.

This reminds me of an Admiralty Court case I heard of. The presiding judge said that the argument that there was no "risk of collision" between the two vessels is disproven by the fact that there was one.

The argument that the bolt breakage was not due to over torqueing is disproved by the fact that the bolt broke.

The bolt broke because its torque limit was exceeded. Imagine if the hole was drilled only half as deep as it should have been. Would it have been “OK” for the tuner to break it trying to get the head flush with the plate?

There may be many bolt holes that are not concentric enough with the plate to allow full contact. That does not mean that the fastening system is not satisfactory. And it certainly does not mean that the bolts should be torqued to the failing point to try to accomplish full contact.

If I was the owner, I would be tempted to just place a couple sawed off bolt heads in the holes with stickum. The piano probably doesn’t need every single one of them. There are lots of trucks on the road that are missing a lug nut and get along fine. The piano hasn’t exploded or warped or anything. More harm than good could occur if the tuner doesn’t have the right tools and know what he is doing.

But if I really wanted this repaired like new, I would ask Kawaii to send a tuner they approve of and then I would send a bill to the tuner that broke the bolts. If he refuses to pay, that is what small claims court is for. With documentation from Kawaii, I don’t see a lawyer being necessary.

One thing I would not do is let the original tuner try to fix it himself.

In my former life as an auto mechanic, removing broken bolts was a frequent task, given the rust and corrosion experienced on cars and trucks.

I once removed a broken head bolt on a Volvo 4 cylinder. The bolt was sheared off at about a 45 degree angle, about 2 inches down inside the block. (I did not break it...the owner did, and towed the car to the shop).

That one took a while, center-punching at an angle was tricky, then drilling successive pilot holes, then a hole big enough for an easy-out.

Suggestion...get a skilled auto mechanic to take out the bolts. Or a motorcycle mechanic, because they are trained to not only do such work, but also with care for the cosmetics of the bike, something that is not always as important on the machinery of a car or truck.

Also, although it looks like the hole is not concentric, and that may be the cause, it also could be a batch of faulty bolts, not an unheard of happenstance.

Jeff

That quote makes this discussion worthwhile!



Knocking out the double negative, the argument is that the bolt breakage was due to over torqueing is proven by the fact that the bolt broke.

That would be certainly be true if over torquing is the only reason a bolt breaks. It would almost certainly be true if the holes and the plate were concentric. It is questionable when the holes are offset as much as possible, as here.

My question to Kawai is why would anyone want to spend $25,000 or more on one of their pianos once they knew the screws in the wood might not be properly aligned with the holes in the plate? Is there a good reason other than it's securely fastened and that's the way it is?

Otherwise I agree with your remedy.

PS Now Don Mannino has said Kawai are looking after the piano, I'd note the compliments paid to them in this thread. Wise to advise warranty problems rather than try to fix them!

On the third pic the OP uploaded to photobucket, this one:


What is the vertical line on the rim, toward the end of the strut and to the left of the shadow, at the top of the picture?

A pencil casting its shadow.

I spoke with our new service manager today, and he told me that he is working with the owner's piano technician to replace these broken bolts. He will remove the broken stems and install new bolts at Kawai's expense.

It is better that way. Take care of the customer, and worry about the details later.

Now that's class!

Hats off to Kawai for such a no-fuss approach!

On a technical level I'd be very interested to see or read how the stems/shanks of the bolts will be removed.

Its great that this issue will be taken care of by Kawai. In the many years working in industry as a T&D/machinist, I have had to remove hundreds of broken bolts (as large as 3" diameter) and even HSS and carbide taps that have sheared or broken into recesses. Each case will offer its own remedy, depending on the circumstances of how they broke, the materials your dealing with, and the equipment/tooling you have at your disposal.

I have rarely seen philips head screws or bolts shear this way because the forces needed to do so would almost always have to come from an impact driver. Philips head drives have a unique characteristic of stripping/camming out the bit if you apply the kind of force needed to shear the head off or if you tip the driver off alignment. With impact drivers, all bets are off. The rapid motion of force application can put stresses onto bolts that far exceed their design limitations.

The manufacturing process for fasteners will often produce a certain amount of defects that get by QA. On auto feeding screw machines the end of the bar stock will often be much harder/more brittle because of the high heat from high speed saw cuts from the supplier. Some manufacturers toss these end peices, others don't. Hammer forging of the heads will also work harden many materials somewhat unpredictably. Dirt or debris in the forming dies can create occlusions or inconsistancies in the radius between the head and the stem; a chipped tool tip on a cutter can also creat a sharp corner at this point instead of a radius.

The methods to remove the remanants can vary. I usually begin with trying an angled punch on the perimeter, working back an forth in both directions.

I try and avoid easy outs or other left hand drive extractors if the application does not lend itself to deal with breaking one of these off in the bolt. With wood being around the hole, a sink type EDM tap remover is out of the question since you would get contamination from the fluid needed in the process. Setting up a rigid machine with carbide endmills can also be expensive if you break off an easy out.

A really good way to remove these that has not been mentioned is to grind the top of the break flat with a carbide burr on a dremel type tool. You then grind or punch a concave starter dimple into the center of it. Then you progressively drill down through the bolt going up in drill sizes until you approach the thread diameter. At some point, the drill will break through one side of the threaded perimeter because its near impossible to stay perfecly centered. You then use a punch to colapse the thin thread wall left into the drilled cavity and yank it out using needle nose pliers, Kelly's forcepts or a curved tip pic.

If the wood gets mangled a bit you can always coat it with epoxy, and drive in a new screw with a layer of teflon plumbers tape on the thread as a release agent.

I thought I would post the resolution to this problem. A technician was at my house today and removed and replaced both broken bolts. The way they were extracted was by essentially cutting a slit with a variable speed dremel for a flat head screw driver and then backing the screws out. Thanks to all who gave input, it was extremely valuable to the resolution of this issue.