Piano World Home Page Forums Our Most Popular Forums Piano Tuner-Technicians Forum Hammer shank broken close to head, temporary repair methods?

The long run solution is to replace the shank but what short term measures are available?

My thought is to glue the head back on to the shank, drill a 1 mm diameter hole down into the centre of the shank from the top of the head, about one inch deep, and then fill this with a carbon fibre rod and adhesive to provide strength and flexibility.

Has anyone tried this or similar, or is there a better method? The break is too close to the head for twine or tubes to be used.

Hi Ian,

I'm not a technician but I can tell you what I found in a grand piano I recently acquired. My technician and I are going to work together replacing the hammers. He came over with the new set and we started discussing the next step (either removing each old hammer from its shank and installing the new one or installing the new hammers on new shanks). The C8 hammer was already broken off, so we removed the next two assemblies to help me get an idea of what hammer replacement entails. He got his hammer off in a minute or so, but as I fiddled with mine, I noticed it was secured with a big gob of glue. Removing that revealed that the shank was broken. The light gradually dawned as I understood why that shank had a hole in its end: someone had drilled through the broken end lodged in the hammer and into the end of the shank, driven a thin metal rod in, and glued the mess back together. There was no way to tell how long ago this repair was done, but the old glue was significantly yellowed and brittle so it certainly wasn't a recent one.

I think that would be a pretty easy repair if you have a drill press handy.

Andy

A simle toothpick or even nothing can be enough just to wait for a new shank

use a drop of cyano on one side and white glue on the other.
It will not break if the part is well positioned.

Perhaps you should elaborate on this mixing of two completely different glue types, one which relies on evaportation of water, the other which relies on chemical reaction to set.

Myself, I would use a thicker CA glue alone for a quick fix and maybe zap it with a kicker.

hello . The drop of cyano is just there because it set soon then no need to hold the parts together when it is not easy. the white glue seem to hold well in that case once cured. it also fulfill any hole or missing wood, may be making a stronger joint.

cyano alone on wood I try to avoid, but I dont buy the special qualities sold for wood (gel or thickened cyano I suppose)

even white glue alone is enough to glue a broken shank.
I have the one used by Renner to assemble their parts : fast cure and harden well.

For the time spent fiddling with the alignment of the broken parts, then trying to drill a 1 mm hole down the center and glue in a reinforcing spine, it is faster and easier to do the permanent and proper repair with a new shank.

Ditto. Just fix it right and be done with it.

True, but you have to have the shank with you!

I always carry those with me. They make great plugs for stripped holes.

I carry a lot of shanks for verticals, both sizes, but grand shanks come in several shapes and sizes. Matching grand shanks is difficult.

True but, he didn't say it was a grand or vertical. Use ca then.

It's a grand shank so CA or Titebond looks like the answer. Another use for a toothpick! Thank you one and all for your advice.

The trickiest part of this repair is getting the two pieces to line up exactly. Once you put the CA in the parts, you only have one shot at it.

When they break at the head they leave numerous "stalactites" hanging down that have to be matched back up with the other part. They are fragile so you must take care not to bend them or you won't get a good joint. It's a good idea to do a dry fit first to make sure the pieces will go back together.

My preferred method is to use a drop of water thin CA on each part. It penetrates into the wood really well. I follow with a drop of thicker CA just on one part. Carefully fit the pieces back together, and clean up any squeeze out that may drip or run down the shank. then put the hammer back in rest position and align with the other hammers. Lastly I give it a spritz of accelerator.

Success depends largely on how much practice you have had using CA for these types of repairs. CA can be terrible stuff if not used correctly! It can easily create more problems than it solves. Especially be careful of the thin stuff, because it has a huge potential to run and travel very quickly to places you don't want it.

I service pianos that I did this to many years ago and the repair is holding up fine. YMMV.

Replacement is the best option, of course. If you are intent on repairing using the original shank, then at least do that properly. Cut the shank off at a low angel so that the cut surface is at least 2" / 5 cm long. Cut the same angle on a new piece of wood to be glued on. This is called a scarf joint. Glue with a hard setting glue. Then hang the old hammer on the new shank end.

Ah Jûrgen ! always trying to sell a piece of wood (half shank to replace the broken part)

As asked originally it was a "temporary fix" !

What is less easy is when the shank is made in an unusual wood as cedar, most replacement are stiffer and have to be cut in an angle shape along some lenght for supplenes

I've successfully used CA for this repair in tight time situations. CA works very fast. Only get one chance when using the accelerator.

I have done this with Titebond a number of times, and there has only been one instance where going back in and replacing the shank was required later; all of the other repairs have held up like the breaks never happened.

Get the right extraction tools, the right repinning tools, the correct grand shank and replace it. It will be an excellent learning experience if nothing else. I've broken several old "repaired" scarfed shanks on both grands and verticals while tuning, so the repairs don't always last.

I always carry vertical shanks, and two grand shanks each for NY Steinway, WNG, Yamaha, and Renner. They weigh nothing and you don't need to schedule a callback. Many times, you can also reuse the original flange and simply repin it to the new grand shank, as long as the knuckle to center pin distance on the new shank matches the original. I did this a few weeks ago with an old Baldwin grand from the 50s. I don't even remember what new shank I used - it might have been a Renner but whatever it was it matched up perfectly with the old shank. I reused the original flange and it was as good as new. (Better, actually.)

Even if you have the right shank/flange combo, it's usually best to repin them anyway - replacements are often too loose.

Thanks to all. I had some Titebond and a clamp to hand so I adopted OperaTenor's solution using an adjacent hammer as a template. One of the bass shanks has been been glued together with twine sometime in the last hundred years or so. I'll see if Abel can provide a couple of replacements.

You don't need something as fancy as a carbon fiber rod, unless you are extremely worried about the increase in touchweight on a very fine piano. Most pianos have friction and weight problems far beyond this already.

You need to do the initial joint with a flexible glue, like PVA or Titebond I. Get the split joint fully engaged, and hammer aligned exactly right for strike and angle.

When the joint is set (give it at least 12 hours), drill a pilot hole using a 1/16" hardened bit on a press. You'll have to make a jig to clamp the assembly. You are drilling parallel to grain lines, so the bit will want to wander.

Use a #6-32 brass screw with a depth of at least 3/4". A smaller screw is preferable, but you'll have to special order it as they don't stock it at most hardware stores at lengths above 1/2".

You want the final pilot hole to be just a bit smaller than the outer diameter of the threads. Hornbeam grain will capture the threads and not compress very well, so if the pilot is too small, you'll risk splitting the shank.

The final stage is sanding the brass screw head and light sanding on the tail. The head can even be inset and filled with a walnut plug if there is an issue in checking.