Forum: music.stackexchange.com
Tags: <tuning><frequency>
Title: Tuning a tuning fork?
Question: I just purchased a new 440 Hz tuning fork.  But several different computer, iPad and iPhone tuners say it's almost half a percent sharp (around 442) of Concert A.  Is there any way to adjust the frequency of a tuning fork?

Answers:
sents: text: OK.
text: I found a quick-and-dirty temporary solution.
text: As an online education forum suggested, a interesting school science experiment might be to see if adding weights and changing their position on a tuning fork will change the frequency of the fork.
text: So I played science student, and tried the experiment.
text: Two big rubber bands on the tines clearly lowered the frequency... by way too much.
text: Next I tried a couple strips of masking tape wrapped around the very end of the each tuning fork tine.
text: That also lowered the frequency, by only a bit too much, to 20 cents flat.
text: So I removed those pieces of tape and carefully measured them.
text: Then I cut some tape strips about 9/29ths as long (actually a few mm longer).
text: Wrapped the new lengths of tape on the fork tines, and the fork rang 3 cents flat.
text: A little more fine trimming of the length of the tape with some sharp scissors, and I got the fork to measure within +-1 cent of 440 Hz, as measured against several calibrated iPhone tuners (both dial and strobe).
text: The fork also now sounds good when played simultaneously with an mp3 of a 440 Hz tone to check for beats.
text: The tone probably isn't as pure, and tape will eventually age and wear, but this quick fix should work well enough until my next trip to a good music store for a better quality tuning fork.
answer_details: author: music.stackexchange.com/users/1489/hotpaw2
score: 28
sents: text: You could tune it up if you have precision tools that can grind off just the right amount of metal from each tine (this would increase the frequency; to decrease the frequency you would need to add metal!) - but practically speaking that means no, you can't do it.
text: Does it look damaged?
text: If not it is probably supposed to be a 442 tuning fork.
text: If you need a 440 you'll need to just buy one.
text: Update based on the comment that you had bought a 440 fork: Take it back to the shop, get them to check it.
text: If their check shows it is a 442 then they can replace it.
text: If they show it to be a 440 then maybe your tuners are out.
answer_details: author: music.stackexchange.com/users/104/Doktor Mayhem
score: 18
sents: text: It is defective.
text: Return it for a refund.
text: There is no practical way to recalibrate it.
text: The reason people purchase a tuning fork in the first place is to get something that is exactly calibrated already.
answer_details: author: music.stackexchange.com/users/None/
score: 9
sents: text: Interesting question!
text: No-one's mentioned temperature, so far.
text: I'm off to put one in the freezer and another in the oven!
text: I'll report back!
text: Just got back from hospital with frostbite on one hand and burns to the other...
text: but surprisingly the tuning fork stayed in pitch!
text: My theory stemmed from the British Yard which lives in London.
text: It is exactly a yard long at a given temperature.
text: Longer tuning fork =
text: lower note, shorter = higher, surely?
answer_details: author: music.stackexchange.com/users/2808/Tim
score: 8
sents: text: As someone else stated, grinding off material from the end of the tines will increase the pitch.
text: However, grinding material off at the base bend of the fork will lower the pitch: there the material contributes much more to the fork's stiffness than to its inertia.
text: But it may well affect the purity of tone.
answer_details: author: music.stackexchange.com/users/8773/User8773
score: 4
sents: text: I had a cheap allegedly A440 fork that showed sharp on all tuners, and for reference, a better-quality fork showed exactly A. By filing a small amount from the outside of each tine near the join, and checking several times, it is now quite exact.
answer_details: author: music.stackexchange.com/users/71005/R. reed
score: 2
sents: text: A bit of solder at the tip would lower the frequency.
text: But to get both tines exactly right
text: , that's tricky to do.
answer_details: author: music.stackexchange.com/users/1941/200_success
score: 0

Summary of the answers:
It is practically impossible to re-tune a tuning fork.
There is probably no practical way to recalibrate a tuning fork. However, if you are able to, grinding some metal off each tine will increase the pitch whilst adding some solder to the tips may decrease the pitch.