Piano Quality Control & Assurance 5 — Questions and Answers
Question 1: A regulation inspector uses a 'blow distance' measurement during QC. What is blow distance?
- The distance from hammer head to string when the key is at rest (Correct answer)
- The distance the key travels before the hammer begins to move
- The maximum pedal depression distance
- The gap between back check and hammer butt
Correct answer: The distance from hammer head to string when the key is at rest
Blow distance (or 'let-off distance') is the gap between the resting hammer and the strings, affecting hammer travel and tone.
Question 2: Which QC step most directly addresses unevenness in tone volume (one note louder than its neighbors at equal key force)?
- Voicing individual hammers to equalize tonal output (Correct answer)
- Re-regulating key dip
- Adjusting damper timing
- Re-pinning the action flange
Correct answer: Voicing individual hammers to equalize tonal output
Voicing by needling or lacquering hammers adjusts their density, which controls how much energy each hammer transfers to the string.
Question 3: An inspector checks 'string bearing' on the treble bridge using a straightedge. What defect is being screened for?
- Strings lifting off the bridge — indicating insufficient down-bearing that would reduce tone transfer (Correct answer)
- String oxidation or corrosion
- Incorrect string gauges
- Loose bridge screws
Correct answer: Strings lifting off the bridge — indicating insufficient down-bearing that would reduce tone transfer
If strings lift off the bridge, there is no down-bearing and the soundboard receives little or no vibrational energy from those strings.
Question 4: What does 'pinblock integrity' testing assess in a piano QC process?
- The ability of the laminated pinblock to hold tuning pins firmly without slipping (Correct answer)
- Electrical continuity in electronic pianos
- Pin spacing alignment to string layout
- Bridge pin insertion depth
Correct answer: The ability of the laminated pinblock to hold tuning pins firmly without slipping
The pinblock must grip tuning pins tightly enough to hold pitch; failed lamination or splits cause pins to slip and the piano to go out of tune rapidly.
Question 5: During a final QC listening test, a technician identifies a 'thump' on certain bass notes that does not come from the string. What should be investigated first?
- Loose internal components such as screws, felts, or the plate bolts resonating sympathetically (Correct answer)
- String speaking length
- Hammer shank stiffness
- Damper weight
Correct answer: Loose internal components such as screws, felts, or the plate bolts resonating sympathetically
Low-frequency bass notes vibrate at frequencies that cause loose hardware or components inside the case to resonate and produce extraneous thumps.
Question 6: A QC standard specifies 'key travel' of 10 mm for a grand piano. If measured travel is 12 mm, what regulation is out of spec?
- Key dip (the depth the key descends before hitting the front rail punching) (Correct answer)
- Blow distance
- Let-off
- Back check height
Correct answer: Key dip (the depth the key descends before hitting the front rail punching)
Key dip controls how far the key descends; excessive dip makes touch feel heavy and slow, and is corrected by adjusting front rail punchings.
Question 7: Why must piano technicians check for 'knocking' in the action flanges during a QC inspection?
- Worn or broken flange center pins cause parts to wobble, creating noise and inconsistent action response (Correct answer)
- Flanges control key return speed
- Flanges set hammer voicing
- Flange screws adjust let-off
Correct answer: Worn or broken flange center pins cause parts to wobble, creating noise and inconsistent action response
The center pin in each action flange is the pivot for hammers, wippen, and damper levers; worn pins create lateral play that produces knocking sounds and erratic motion.
Piano Quality Control & Assurance 5
A regulation inspector uses a 'blow distance' measurement during QC.
What is blow distance?