Rebushing Grand Hammers

The hammers are de-centred using the de-centring tongs both for removing the pin and then for removing the bushings. These bushings, from 1865, were pulled in using just a trace of glue, as it should be, and the drillings are left perfectly clean with no further work. If traces of cloth adhere to the inside of the drilling, it is necessary to remove them using a 1/8” tapering reamer held between the fingers, making sure that it is inserted always exactly the same amount.

Now is a good time to paper up the forks of the shank and, after screwing in the drop screw, the top of the flange, neither of which can be perfectly cleaned while the shank and flange are attached.

The width of the cloth strip will be roughly three times the diameter of the drilling. It is impossible to get the width any more exact than the distance between the yarns of the cloth, so make a cut roughly where you hope the tear to be and tear a little. If it is too wide, cut diagonally and tear again until the width is as right as possible.

The cloth must never be cut but always torn, so that the edges follow exactly the line of the yarn. Otherwise the bushing strip will quickly and unevenly fray and become unusable or too narrow.

When you are sure you have the width right, tear a strip of 3 or 4 feet in length depending on how many mistakes you intend to make. Each individual strip should be no more than 10 inches long, for reasons that will be explained below.

A simple tool can be quickly put together for making the ends on the strips. Screw together two strips of hardwood to make a clamp about 1½” wide and cut a bevel at about 45 degrees on each jaw, as shown below. Open the jaws to about double the thickness of the cloth and hold the tool in a vice. Pull the cloth down into the top of the clamp, leaving about 2 inches sticking out.

Spread a fairly thick hot glue onto the bit that is sticking out and work it down into the nap of the cloth.

Next draw the glued end into the clamp until the glued length is just short of the end of the jaws, so that there is no glue outside the clamp on the long side.

Draw the clamp very tight, either in the vice or using a G-clamp and leave it for ten minutes or so until the glue will hold. Then remove the strip from the clamp so that it will harden more quickly and proceed to make the remaining strips.

When the glue has hardened sufficiently, use the flush-cutting centre cutters to nip the end down to a width that will easily pass through the drilling. Test it a few times and remove cloth evenly until the point moves freely through the drilling. Any obstruction will cause the cloth to snap.

The picture below shows four finished and and a fifth that awaits the cutters.

Once the ends are quite hard the rebushing can commence. Before inserting the strip, pull the side of the flange where the cloth will enter over a block of wax. This will prevent the extruded glue sticking to the wood and make removal much easier. Now feed the end through the drillings and pull the strip through the shank in a controlled way, keeping the cloth lying straight, on your lap for example, until about ½” is left protruding.

I mentioned above that the strips should be only about 9 inches in length, and the reason is this: as the cloth is drawn through the drillings, no matter how smooth you have made these, it will wear on the outer surface and a little at the edges, so that when you come to broach the bushings for the pins you will find that you need to pull the broach more times through those bushes that were made with the strip when it was new than through those that were done when the strip was nearly finished. If you were to use a longer strip, you would find that this variation was too large and you would need to use larger pins or rebush those that were made with the worn strip. Ideally one would make each bush with a fresh short strip, but that would be very tiresome indeed!

Now wipe a little glue on the protruding end. The picture shows a fair amount of glue just for illustration. The barest wipe over the surface with a fairly thick glue is sufficient. The glue should not be so thin as to be absorbed into the cloth.

There are alternative methods for this work more suited to production, but for the restorer I find the method described quite adequate.

Next pull the cloth until only a small funnel of cloth remains protruding, surrounded by a small ring of glue.

Using a new scalpel, cut the cloth flush on the other side of this fork and pull further until a funnel is left at the inside of the second fork.

Finally cut the cloth flush on the outside. For the hawk-eyed among you, those ends will meet fine once the pin is pressed in in a moment!

You should — now I tell you! — have chosen a cloth that is suited for a certain size of pin, and this pin will be used both for the initial pressing of the cloth and for the final centring, unless you are rich, in which case it doesn’t matter. At any rate the pin used now for pressing should be the same size as the pin finally used for the centre. In this case I am using a pin of 1.25 mm. which is called one number in America and another number in other places. Suffice it to say it’s a fairly thin pin as originally used for the hammers on this piano, and why such fat pins are used nowadays I have no idea.

The pin will be very tight in the bushing and, since it will be used for the centring also, it must not be nicked, so the best way to get it through the bushings is to use a thimble or, since you may not have a thimble, something else suitable like a bench top. It is best to use pins such a Schaff’s with a domed end rather than the sharp-ended European and Japanese pins, since the domed end will find its way more easily to the middle of the funnels. Even so it is important to guide the pin very carefully to the centre of the bushing.

Once the glue is thoroughly dry, remove the pins and trim the funnels flush. You will now understand the use of the wax mentioned above, which not only allows the scalpel to get between the glue and the wood but also provides lubrication for the blade.

It now remains only to broach the bushings and centre the hammers, which I deal with in another article here