Replacing Hammer Heads

Replacing Piano hammers is not a quickly done job. It can appear easy and straightforward to take off the old hammers and and replace them with new ones, but like everything else to do with a piano action, unless the job is done neatly and evenly, the end result will be a poorly sounding piano and a miserable technician! Not what you want after an expensive and time-consuming project.

The cost of a set of piano hammers is more than most people would like to spend on an interesting experiment. If the experiment goes wrong, you will have to spend more money get someone to fix it. A set of new hammer heads must match the old ones. A 5mm difference here or a slight change of angle there, will only guarantee you yet more hassle and grief to get the piano to play properly when you've done all the work.

The first job is to dismantle the action. (The job is similar for a grand piano but for the sake of clarity, the instructions here are for an upright piano.) Disconnecting tapes and taking off the levers will give good access to the hammer flange screws. Take the hammers off, place them on a tray and number them – just in case they, for some reason, get mixed up. Most new hammer heads come already bored - if your set is not already bored, you have yet another 'mountain' to climb. The secret of success in action work is in the precision and care with which it is carried out.  

Removing the old hammer heads from the shanks is done one at a time, using a special tool called a shank extractor. Some technicians like to leave guide hammers on the action so that the new hammers can be lined up to keep the same line as the old ones. Other technicians prefer to take exact measurements from the each hammer as it is being dealt with. If guide hammers are used, it is important to fit the right hammer head to these guide hammers. 

With the old head removed, the shank cleaned of old glue, (any broken shanks replaced) it is quite simple to glue the new hammer head onto the shank. It helps if the fit is firm and snug without being too tight. If the fit is on the tight side, take care not to twist the shank when fitting the new hammer head. Brittle, old shanks break easily.

When ready, refit the hammers back onto the action frame. The ‘noses’ of the new hammers heads should be in a nice straight line. There is a number of ways of replacing hammer heads, all of them are perfectly acceptable if done well. Fitting the hammer heads to new pianos is done in seconds, but away from the factory, dealing with replacement parts it is a much slower process. 

Putting the action back into the piano is the start of another set of very technical adjustments to ensure the proper working of the piano action.

Do not underestimate what is involved in getting a piano to work well. A change to any part in the fabric of the mechanism has a knock-on effect on the function of the action, how the piano plays, and how it sounds. 

If only replacing piano hammers were like replacing a failed light bulb! Then, any careful amateur could do it. But the reality is that replacing hammer heads is not really a job for the amateur - at least not without professional advice and help. 

At best, this article can only be an introduction to the very basics of the job. So please, be careful!

© Steve Burden