Piano World Home Page Forums Our Most Popular Forums Piano Tuner-Technicians Forum Hammer replacement - measurements

I recently picked up a 1989 Baldwin Hamilton 243 for free from a friend.

The only catch, is almost all of the hammer felts are lifting, so I need to replace those. I work on guitars and a variety of things, so although I am new to pianos, I am experienced with tinkering. I found an RPT and had a nice conversation about the piano - he insisted I get this fixed before tuning (I was being impatient!).

However, I am having trouble measuring the bore angle. I looks like the lowest key is 22.5 degrees for the lowest key according to my protractor, which seems much higher than I've read other pianos typically are.

I've removed the action, and the lowest hammer for measurements, so I am measuring:
Key/overall length/Bore distance/hammer width
88 / 0.84375"/ 0.4375"/ 0.40625"
43 / 0.83594" / 0.46875" / 0.4375"
28/ 0.59375" / 0.3125" / 0.375"
1/ 0.875"/ 0.46875" / 0.375"

So my specific questions - does anyone know the standard hammer sizes for the Baldwin 243's off hand?

Is there an "off the shelf" set of these I can order?

Does the bore angle sound reasonable?

Your figures don't seem to make sense.

You coukd contact Ray Negron at Ronsen Piano Hammer. He might know the correct specs.

Pwg

The bore distance of hammers is measured from the tip of the hammer to the center of the hole. It is typically between 2-3/8" and 2-5/8" for upright treble hammers, and about 1/4" to 3/8" less in the bass. So your figures do not make sense at all.

This is a little more complicated than many people think.

Pwg

He tinkers with guitars so changing hammers on a piano should be straightforward.

At least he is starting with a free piano.

Replacing upright hammers without alignment jigs is possible, but you have to be extremely careful or one thing you'll end with is hammers blocking against each other.

I made a spreadsheet to convert the fractional measurements to decimals and I didn't include the 2 and then when I posted here I forgot to add the 2 back to the front. So my measurements are correct, +2.


By "tinkering with guitars" I have done neck resets, bridge reglues, crack repair, refrets, refinishes and kit builds. I was just stating this isn't my first rodeo with precise gluing or using heat/steam to get glue to release. I also build and repair tube amps, recording gear and hifis, recone speakers, and build condenser and ribbon microphones. Like I said, I like to tinker.

My plan to keep them straight would be to redo every other hammer, and I would also be using hot hide glue so it will be very tacky quickly.

I was mostly wondering if anyone else has experience with this on the baldwin 243, and could offer suggestions for replacements.

If you want the most exact match, send the hammers at each side of the brackets to the hammer supplier.

You can get a pretty good idea of the original measurements by looking at hammer #1, #88, and the first tenor hammer above the break.

If you take them out and draw the outline on paper, redrawing the hammer to account for wear (gotta use some imagination) you will be pretty close to what they should be. Then figure out the rake angle as they are not hung at 90° to the shank (this could be 3-5° or so). Then use a protractor to copy the right and left angles and which are bored at 0°. Then remove a hammer and determine the diameter of the bore hole.

Those are your specs.

Pwg

Thank you for the suggestion, I appreciate the advice and will give that a go.

Hi Rob. Don't mind the snarky remarks, I'm also a non-piano tech tinkerer and my attempts (so far successful) at working on my own pianos have sometimes been met the same way.

BDB's advice to send in the hammers is probably the best way to go. Here's a video that goes into a little more detail about that: https://youtu.be/1Pk2K9lNBiU

Good luck!

-Emery

I didn't think I was engaging in snarkerisms.

Pwg

Not you PW, but there are a few that seem to find it, shall I say, amusing that some of us non-techs want to tinker with our own pianos.

What does one do if original hammers have been replaced, and...it is evident that bore angles are wrong, e.g. hammers striking the strings +20 degrees off parallel with the strings in the tenor and middle sections of the piano? Can bore angles be accurately (enough) determined by measuring string angles to the case at the back of the fallboard?

This is a grand piano question. Seems there would be some variation to the method for an upright. If anybody can speak to that situation, it would also be useful to have tht information here.

Good Day to All.

It is easier to determine how the hammers should be bored on an upright. You measure at a perpendicular from the strike point. That is not easy to do on a grand.

In a grand you need to measure the string height, then determine the height of the hammer flange center pin. The difference between the the two is the OPTIMUM hammer bore measurement. If accurately figured, this will put the hammershank parallel to the strings and the hammer at 90° to the strings at strike.

Some like to add 1/32" up to 1/16" to allow for initial filing, fitting and early wear. That is a personal decision...nothing etched in stone. Also a careful craftsman may take into account that string heights can differ in different parts of the piano and may alter dimensions accordingly.

In an upright it is not quite so cut and dried. Essentially you are looking to establish a bore length that will give you roughly 1 3/4" - 1 7/8" or so hammer travel when the hammer rest rail is where you want it. There is a rake angle to be considered also. Some if this can only best be determined by doing some regulating on the action and analyze how things are shaping up. Tricky sometimes even for the experienced tech let alone a newbie or tinkerer. Not saying it can't be done...just warning. I have seen the results of well intentioned tinkering. Like I have said before...you don't know what you don't know". If you're okay with diving in and then doing it all over again when you realize: "Oh, I didn't know about that...oops..." then go ahead.

This is not rocket science...but neither is it always totally OBVIOUS. There are numerous factors to be yaken into consideration.

Pwg

So... bore angle is the angle off the perpendicular in the vertical plane (forwards to backwards as seen from above looking at the hammer head)?
and rake angle - is how far from 90 degrees to one side or another? My admittedly untutored guess about determining rake angle was to measure string angles from front to back of the piano.

And, yes, string height is different in different parts of my grand piano. The 20 bass strings are a few mm lower than the plain wire strings further up the piano. Can't recall now for sure, but I think all the plain wire strings were the same height.

Bore angle is matching or coming close to the angle of the unisons as seen from above.

Rake angle is at the hamnershank...the angle that the hammer is hung relative to the shank from the side. It is typically 90° for the majority. Treble construction might require a more acute angle. Determined empirically.

This is for a grand. Does not apply to an upright!

Pwg

Thank you Emery for speaking up. The snarkiness was not called for. The person asking the questions is a guitar repair person interested in pianos. I personally pay close attention to what guitar repair people have to say.