For the piano techs: loose leg screw help needed

[jziegler]

If any of the piano techs on here see this, I need a little piano help.

My wife has a baby grand piano that's 90+ years old and was her grandmothers (possibly great-grandmother's, I'm not quite sure). She is planning to have it moved to a different location soon (she is a voice teacher, and recently purchased a music school where she now does all of her teaching). The last time we had the piano moved, the screws holding the legs were very loose, and the piano movers had a hard time with them. So, my question is, what is the best way to fix this so it won't be a problem in the future? Are there larger screws, something that I can put in the screw holes to tighten it (done with toothpicks in the past, and didn't work well the last time), threaded inserts? I'd prefer a solution that I'd be able to undertake one leg at a time without moving the piano, I don't think the movers would like me taking a bunch of time to work on it in the middle of their job.

Thanks!

[JimD]

Without seeing the joint - or knowing more about pianos than I know - I am not sure what solutions would be best. If these are hanger bolts - devices with wood threads on one end and a normal bolt thread on the other end, then there are larger and longer ones available at a big box store (home depot or Lowes) or hardware store. A longer one only works if there is signficant additional wood behind the end of the existing piece.

If the bolt already goes in about as far as it can, then a threaded insert would appear to be necessary. I would go to McMaster Carr (mail order) for those but you might find something locally that would work. I prefer the brass or brass plated steel inserts, not the zinc ones. The local stores around me have the zinc. The issue is zinc creeps - it does not stay completely rigid. So a zinc threaded insert doesn't make as good a connection as a brass or brass plated steel insert. I like to put threaded inserts in with epoxy in addition to the threads that are typically on the outside of them.

With either threaded inserts or longer hanger bolts, a significant issue is drilling the right size and depth pilot hole. I like to use a scrap piece of wood as the stop (plus also some tape over the piano piece in this case) to be absolutely sure I won't go too deep. Brad point bits are also prefereble. Forsteners would be good for the insert if you can start them. A drill press or a drill guide would be nice.

Jim

[Mr__Bill]

The last time I helped to move a grand, about 35 years ago, I was one of the dumb helpers. As I remember the screws went into threaded inserts and the screws were brass with a Phillips head. This was a piano that was moved a lot. From an orchestra pit to storage and back it rolled on a steel framework with large casters but when it went off site it was broken down and flipped on it's side. That's when the legs and peddles were taken off. When it was moves on it's side the piano was de-tuned and then re-tuned after being set up again. I was told that releasing the tension lessened the chance of the harp being damaged by the stress of moving. The mover also had a padded bag with handles that just fit the piano and completely enclosed it and separate smaller bags for the legs and peddles. The paid help then moved the piano on a special dolly that strapped on to the piano and had straps for lifting it at stairs. The dumb helpers got to carry the legs. They had a truck with a padded side where the piano rode strapped to it.

At the destination the piano was reassembled and allowed to set for overnight to acclimate prior to the piano tuner tuning it.

Bill

Edit: I see I took too long to respond and Jim already mentioned the threaded inserts, so this is the second vote for them.

[tommyt654]

Assuming they are wood screws why not fill the hole in with wood putty and see if they'll hold?

[Joe DeFazio]

If any of the piano techs on here see this, I need a little piano help.

My wife has a baby grand piano that's 90+ years old and was her grandmothers (possibly great-grandmother's, I'm not quite sure). She is planning to have it moved to a different location soon (she is a voice teacher, and recently purchased a music school where she now does all of her teaching). The last time we had the piano moved, the screws holding the legs were very loose, and the piano movers had a hard time with them. So, my question is, what is the best way to fix this so it won't be a problem in the future? Are there larger screws, something that I can put in the screw holes to tighten it (done with toothpicks in the past, and didn't work well the last time), threaded inserts? I'd prefer a solution that I'd be able to undertake one leg at a time without moving the piano, I don't think the movers would like me taking a bunch of time to work on it in the middle of their job.

Thanks!

As a piano technician, my first recommendation would be to have a professional piano technician repair the legs for you. The reason that I will recommend this first is because pianos do fall, sometimes with quite disastrous or injurious results. I have seen (and repaired) the aftermath of quite a few fallen grand pianos, including one in which the rear leg literally exploded into 15 or 20 chunks of wood that went flying in all directions, causing the piano tail to crash to the ground, largely destroying the lyre (pedals) in the process. It was a miracle that no one was seriously injured.

If you are set on doing this yourself, the first thing to do is to investigate and understand the leg attachment mechanism. On most 90+ year old pianos, each leg is held in place by a pair of metal plates that form a tapered sliding dovetail joint. Most of the time (but not always), the joint is tightened as the leg slides outward (away from the center of the piano). Once the joint is tight, either a rotating cam or, more likely in your case from what you have described, a pair of screws goes up through the leg's "shoulders" (or horizontal top section) locking the sliding dovetailed plates together. So, in this configuration, the screws are not holding the legs on, the plates are, and the screws keep the plates locked together.

If you remove a leg and find that this is indeed the mechanism used, then you should check the following items and then deal with the stripped screw holes:

First, assess the condition of the joint between the vertical part of the leg and the horizontal leg shoulder. Almost always this joint is a large round wedged tenon joint (the vertical part forms the tenon that goes through a hole in the horizontal shoulder, and is held in place by a wooden wedge driven and glued into the split tenon). If that joint is very solid, good; if not, repair it. You will have to remove the plate to repair it. Hide glue will have been used; you can re-amalgamate it using vinegar (acetic acid) during your repairs if necessary.

Next, check that the plates are not cracked, and that the screws holding the plates in place are not stripped. If they are cracked, have a piano technician replace the plates and finish the repairs. If they are in good shape and slide together tightly, then just tighten the screws that hold the plates in place. These are not hardware-store variety screws; they are much fatter and stronger than anything you can buy today. So, crank the snot out of them.

Next, temporarily reinstall the leg, using a mallet to drive the plates together as tightly as they will go. Now, using a flashlight, assess the way the screw holes in the shoulder and the screw holes in the keybed (the bottom of the piano) line up. With the leg plates mated together as tightly as they will go, the screw holes should line up perfectly (even though the wood is stripped). If they line up perfectly, you can repair the stripped screw holes. You have several options here. You can drill out the screw hole with a forstner bit, and glue in a plug (*not* a dowel; a plug with the proper grain orientation). Then, reinstall the leg, use a mallet to mate the plates as tightly as possible, and then clamp the leg in place and drill new screw holes. This is by far the best repair, and the one I recommend.

Or, remove the lid and lid hinges, put the piano on its side (long or bass side down; take off the front bass (left) leg and probably the lyre in order to do this; check the tightness of the other legs first, and have *plenty* of help), and partially fill the hole with a filler of a fibrous and flexible nature and glue. Toothpicks usually fail. Veneer strips often fail. Thin strips of leather glued in place (make a slender "tent" with the screw as the tent pole) sometimes work. Believe it or not, a fair number of techs are reporting success with paper towels glued in place with CA glue ( I have used this technique but not on a leg). You can first spray the screw with a mold release or teflon spray so that the glue does not stick to it. Marine epoxy with a dedicated epoxy filler like microfibers or colloidal silica also works very well. Typical wood putty will fail. Some modern wood fillers such as a two part polyurethane wood filler may work; you will have to experiment on scraps to assess their strength before committing to using them.

If the screw holes do not line up perfectly, and especially if they line up so that when you insert the screw the plates will partially unmate, then you have a problem (and this is a fairly common problem). The screw *must* hold the plates tightly locked together or the plates will fail down the road and the piano will fall off of its leg. So, if this is the case, do *not* use any of the filler ideas; plug and redrill the holes, as I outlined above. Or, make some cams and switch to the camlock system (if you visit a piano store and crawl under a few grands, you will quickly see how that works).

*Do Not* use longer screws; they will protrude through into the action cavity and into the keyframe, making the soft pedal inoperable and probably altering the key bedding (which causes other problems I won't detail here). Although fatter screws might work, you most likely won't be able to find any. The threaded insert idea sounds great in theory, but in practice it is very hard to install the insert in the perfect place that keeps the metal plates as tightly locked as possible.

---

If the legs are *not* held together by metal plates, and if indeed the screws are the main fasteners for the legs (there will probably be some small dowels for alignment sticking up from the leg shoulders in this circumstance), then use the forstner bit and plug method of repair outlined above. Here, I would use a good marine epoxy to glue the plugs in, since their function is more critical than in the plates scenario.

Good luck with it; be safe; always keep some large items such as sturdy chairs under the piano if you are under it with a leg off (presumably you will use a jack to lift one corner of the piano in order to remove a leg, but assume that the jack will fail and position other items to take the weight of the piano if that occurs, instead of being suffocated). And, once again, my first recommendation is to hire a good piano technician to do the repairs for you. You can find one through the Piano Technicians' Guild. I would try to find one who is a rebuilder, not just a tuner, if possible.

Joe DeFazio
Piano Technician

[jziegler]

Joe,

Thanks very much for the detailed information. I'm not sure which method is used, it was around 7 years ago when I was around for the movers moving the piano into the house, and I wasn't paying that much attention. But in either case, I like the sound of the plug method. Is there a specific species of wood that should be used, or is any decent hardwood acceptable?

We have used a registered piano technician for all of the tuning, and he has a decently long history with this piano, doing a partial rebuild on it 20-30 years ago. He would probably require the piano be moved to his shop for this kind of work, and the additional moving expenses would be outside of our current budget. I don't want to take away for your line of work, but in the current situation, I will probably need to do this myself. I'll be sure to post a followup on how this turns out.

Thanks,
Jim

[phrog]

Very interesting Joe De Fazio. I never thought of something like this being so complicated.

[Joe DeFazio]

Joe,

Thanks very much for the detailed information. I'm not sure which method is used, it was around 7 years ago when I was around for the movers moving the piano into the house, and I wasn't paying that much attention. But in either case, I like the sound of the plug method. Is there a specific species of wood that should be used, or is any decent hardwood acceptable?

We have used a registered piano technician for all of the tuning, and he has a decently long history with this piano, doing a partial rebuild on it 20-30 years ago. He would probably require the piano be moved to his shop for this kind of work, and the additional moving expenses would be outside of our current budget. I don't want to take away for your line of work, but in the current situation, I will probably need to do this myself. I'll be sure to post a followup on how this turns out.

Thanks,
Jim

Hi Jim,

Any fine grained hardwood would work. So would old-growth dense spruce or heart pine, for that matter. That is most likely what the keybed was made out of in the first place. Poplar and basswood are easy to work and inexpensive.

Make sure that you measure the interior dimension of the screw (between the threads), and drill a pilot hole that size, or a few thousandths larger if you use a very dense wood like sugar maple. We typically drill a pilot as described, and then partially re-drill with a larger bit and depth stop for upper part of the screw before the threads start. In many legs, that larger part will be entirely within the leg shoulder, so you will probably not need to drill the larger diameter. But check, just in case. If you are using a hard wood for your plugs, do use paraffin or similar to help those huge threads to cut into the plug more easily.

I do most repairs like this in the customer's home. I am not going to comment on what course of action your RPT may choose; he might see a good reason to bring it to the shop (which, yes, would get expensive), or he may choose to do it there. Either could be a good choice, depending on his diagnosis and comfort level.

You might ask him to take a look at it and give you an estimate, if he happens to be in the neighborhood sometime doing a tuning.

Good luck with it,

Joe

[wardprobst]

It's way easier to fix this problem with piano on its side on the skid board. The main problem you would have is having to hurry while the movers were waiting. I would suggest you talk with them to see if they could turn it before lunch and then go to lunch that would give you or your piano technician an hour to make the repair. Like Joe D. I'd suggest having your tech do it because he will have had experience. For reference, each leg carries a minimum of 200 to as much as 400 or more pounds depending upon the size and make. It can be done before you attempt move it also without too much trouble but it would take longer because you have to jack up each leg, remove it, fill the holes, etc. There is a tool called a Grand Piano Transporter that lifts them all at one time which would save some time but not many movers carry them.
Hope this helps,
Dale Probst
Registered Piano Technician

[jziegler]

Ward and Joe,

Thanks for the advice, and I did go ahead and do the work myself yesterday. Only the two front legs needed work, the back one is still held in pretty well.

The legs are of the second type that Joe described. One large dowel (at least 1" diameter) on each side of the leg shoulder. I jacked the legs up one at a time (I built a platform for my car jack with 2x6s, and a couple 2x4s with a cross piece going up to about 1/4" below the piano. Drilled out the screw holes with a forstner bit, and then plugged with poplar epoxied in.

Once again, I appreciate the advice, and probably would have called an RPT for this if it weren't for the tight time schedule and current financial considerations for the new business.

Jim