Piano World Home Page Forums Our Most Popular Forums Piano Tuner-Technicians Forum Best lubricant to use on Una Corda return spring

My new August Forster 215 has developed a squeak when pressing the Una Corda pedal. Using a stethoscope, I found that it's the metal leaf spring that returns the action after the pedal is depressed (wood/metal contact). I'm at odds in regard to the type of lube to use, Talc, PTFE powder, Graphite. I'm hesitant to use the PTFE as some particles could somehow drift upward towards to pinblock. What are the factories using?

Any advice here is greatly. appreciated.

The first thing to check is whether the screws that hold the spring in place are tight. But really, your piano is new enough that the dealer should take care or this.

I hesitate to use any lubricant, because it wears off. There may be some roughness on the edge of the spring. The technician should check for that, and ease it if necessary.

The most durable treatment for the keyframe to spring contact I have found is burnished graphite. Not paste, but stick graphite rubbed into raw wood and then burnished with a smooth steel burnisher.
Regards,

I have had great success with polishing the leaf spring, sanding the wood surface to 320 grit, and applying a ptfe in a solvent solution.

No worry about teflon powder getting in the tuning pins. If the pins fit so sloppy that the powder could get in, the pinblock is shot.

Thanks to everyone for the input, it's most appreciated.

I'm intrigued by the polishing of the spring approach - not only do I get a squeak (when pushing the Una Corda pedal quickly) but also creak from the same area if the movement is minute (such as when I'm playing and holding the pedal but shift my weight on the bench and move the pedal very slightly). Do noises typically come from a wood to metal surface being too rough or too smooth? (assuming no lubricant).

You need a powered buffing wheel to do final polish on the leaf spring. Be sure to round the edges so it reduces wear.

Polishing alone might solve the squeak. But you could also get the squeak you are describing from a balance rail stud that is slightly loose in the keyframe

The squeak is from a stick/slip phenomenon, sometimes called sticktion. This tends to occur with smooth surfaces more than rough surfaces, I think. Nonetheless, there's a good chance that PTFE or graphite as recommended will solve the problem.

I have to try PTFE powder on violin bow...

That would certainly make me sound better on the violin!

Are you sure the squeak is not in the bench?

Or the sole of the shoe on the pedal?

I'm using a stethoscope to confirm the source (Return Spring against keyframe) - One tech is advising that he uses Candle wax as lubricant on the edges of the keyframe. If it's 100% paraffin, any danger of softening the wood?

Why are you dealing with this yourself? Ask the technician to deal with it when the piano is tuned, or get it fixed under warranty.