Harp Lever / Sharping Lever

The photo shows one of these levers (with a brass bead) posed (but not installed) on a harp. Other levers in the photo are Musicmakers Universal levers.

Most harps are diatonic - the strings are tuned to a single major scale, usually C. To play in another key, some strings must have their pitch changed. For example, with a C-tuned harp, to play in the key of G, the F strings would have to be changed to play F#.

Big orchestral harps have pedals that engage special mechanisms at the top of each string, to change the pitch of those strings. A given pedal can change all the F strings to F# strings, for example.

Smaller harps ("Folk" or “Celtic”) either do without, or implement a simpler mechanism: the lever. A lever is a device that is fixed near the top of a string. When the lever is down ("off") the string vibrates its full length. When the lever is up ("on") the string vibrates a shorter length, playing a higher (sharped) note. Levers can only sharp a string, but there are ways around that limitation.

Commercially-available levers are $15 and up. A small harp may have around 26 strings; many have more - 36 strings is common. So adding a lever to each string runs about $400 and up. Some harps use fewer levers, as a cost-savings. Who needs E# anyway?

But wait! What if there were some less-expensive levers?

Well, Good News!

Print some of these, assemble and install them. I used PLA. Assembly consists of pushing the handle part through the base part and installing the string bearing.

The string bearing is the small round piece. it fits very tightly on the short peg on the handle. I use parallel-jaw pliers for the task. Regular pliers would work, too. Put some masking tape on the jaws to avoid marring the parts. A piece of dowel and a light hammer might work, too - I haven't tried it.

I was concerned that using plastic (PLA) for the string bearing would be a problem, but it works fine. The design was made to allow these brass beads to be used:
https://www.amazon.com/gp/product/B08ZJ11NM6

The lever must be fastened down to work properly. An eensy-weensy bit of graphite powder may be useful. Do you have a pencil sharpener?

If the lever is too loose, a shim of paper under it can help. Tightness can be adjusted by how firmly the mounting screws are torqued.

Consider printing the handles for the C and F levers in red and blue, respectively. 

The groove in the string bearing may be too small for larger-diameter strings. A needle file or some deft Dremel skills can fix that. Or print your own - the outer diameter is 5.86mm, the hole is 3mm. The thickness doesn't matter much - this one is 3mm. I added a file with a 4mm and a 5mm, which work fine.

I designed this in Tinkercad. Yes, really. (You can tell, can't you? Don't lie to me.)