By Gregory P. Cheng, RPT
Purpose: To correct the travel and angle of the hammer from rest to the string.
Inspection: Using a straight edge, lift a section of hammers and observe the angle and movement of the hammers. Hammers that move side to side while lifting the string level need to be travelled and burned. Hammers that are not square need to be burned.
Procedure: Travel the hammer by shimming the appropriate side of the flange. Then heat up the shank to introduce a twist in the shank to square the hammer.
Final Inspection: Using a straight edge lift a section of hammers and observe the angle and movement of the hammers. The hammers should rise from rest position parallel and square to each other while maintaining square to the strings.
Travel tape (Schaff Part# 6025)
Straight edge (Schaff Key Leveling Gauge Part# R-26)
Traveling and twisting hammers is easy. If you have just filed or replaced a set of hammers, you will most likely need to travel and twist the hammers. (Note: if the piano is in good voice and/or has distinguished string grooves, and you are not filing the hammers to fresh felt below the string grooves, I advise against traveling and twisting. The piano may technically be “wrong,” however the voicing and tone of the piano win out in priority. Correcting one issue without looking at the whole picture will introduce another issue. In this case, it would be ruining the voicing for the sake of properly traveled hammers.)
Traveling the hammers is the first step in this process. With the action on the bench, slip a straight edge under a section of hammers. Lift the section of hammers from rest to the string height position. This usually means the hammer will be rising approximately from 4 o’clock position to the 3 o’clock position. Raising them higher than that will not give accurate information, and since hammers will not raise higher than the string in the piano, a higher measurement is useless.
Take note of the hammers, do they all travel parallel to each other, or do some move toward or away from the adjacent hammer?
Note the offending hammer. Unscrew the hammer flange. Insert travel paper or travel tape on the underside of the flange next to the screw hole, on the side of the flange the hammer is traveling in.
Reinstall the flange on the flange rail, remembering to back out the flange screw to click into the original threads before turning down and tightening into place.
Reinspect the hammer in question. Is it traveling properly now or does it need more travel tape? Is it traveling in the opposite direction? Correct by adding or moving travel tape as necessary.
Under no circumstance should travel paper or tape be used on both sides of the flange. If you find this, correct it by removing both sides and start fresh. In addition to this, clean work is good work. I was once told by a tech that I should leave my travel paper sticking out of the flange rail to show that I traveled the hammers. My response to this was that the way I show that I traveled the hammer is that they are going to travel properly. Anytime I see travel paper sticking out, I immediately check to see if the hammers are traveled properly. Nine times out of ten they were only half-heartedly traveled.
Repeat these steps for all sections of the action. To keep a consistently fast pace and improve accuracy, I tend to work in a three-phase process: Initially, I go through and find the worst offenders, correct them, and move on. The second time through, the worst offenders may not have been as bad as the first time through, but they appear more readily and are easier to spot. The final run-through is a nit-picking exercise and final correction. Again, the offenders may be subtle but you will see them more readily. Inspect, correct, and move on.
I use my rule of threes for all my regulating procedures. The work goes by quickly, you sneak up on accuracy, and you don’t get lost in the process because you're only ever changing the big things. When doing the same process 88 times it is easy to fake yourself out and start over correcting. Stick to the rule of threes and you will never get lost.
Once you have traveled the hammers, it is time to twist the shanks. You will have noticed that in the process of traveling the hammers, you now have hammers angled incorrectly.
Hammer 52 is incorrect.
Heat up the shank using the heat gun. Hold the heat gun three to six inches away from the shank, and move the heat gun parallel to the shank up and down to heat the entire shank. Be careful not to burn the knuckle or hammer felt. The goal here is to heat the shank without charring the shank or introducing burn marks. The heating process should not take longer than 20-30 seconds. Turn off the heat gun and safely set it aside. Introduce a twist in the shank by rotating and holding the hammer in the direction that would correct the hammer. Overcorrecting during the twist is necessary. Release the hammer and inspect for further correction. Please note the goal here is to twist the shank, NOT to heat the glue and twist the hammer itself.
Hammer 52 is now correct.
Repeat as necessary through the piano.
For further reading please consult: Upright and Grand Piano Action Regulation by Carl-Johann Forss, Chapter 7 pages 261-278; PTG PACE Grand Regulation Lesson 22, Part 3; Grand Regulation Touch and Tone by Danny Boone, Page 37-44.