Why does my newly bought tuning fork seem filed?

[Enrique]

The body of the tuning fork consists of a U-shaped rod. The two ends of the U clearly show having been filed. What can possibly be the reason for that? It's not the first one in which I've noticed it.

[Euan Mackinnon]

I would guess that filing is used to raise or lower the pitch very slightly in order to make it precisely the pitch required.

[Enrique]

Thanks Euan. I guessed something like that could be the cause but, in that case, the two arms of the U would not have exactly the same length after the filing and perhaps this would cause some spurious harmonics. Anyways, I guess this would be a question approppriate for a physicist in the field of acoustics although, if everybody has always seen these marks in tuning forks then no need to consult an specialist.

[Joy]

It seems I read about this sometime ago and if I remember correctly that if the pitch of the fork needs to be raised, then you want to file/grind some of the metal from the top ends of the fork, and that makes it shorter. If the pitch of the fork needs to be lowered, then you want to put a notch/file/grind between the tines on the bottom of the 'u' to make them longer.

[Enrique]

That's useful information, Joy. I always had a very chip fork, and was always in doubt about the frecuencies I heard (if a good one, only one frequency shoud be heard). Sometimes, it seemed to have several. The day before yesterday I finally made up my mind to buy a new one. Thanks for your post.

[Joy]

That's useful information, Joy. I always had a very chip fork, and was always in doubt about the frecuencies I heard (if a good one, only one frequency shoud be heard). Sometimes, it seemed to have several. The day before yesterday I finally made up my mind to buy a new one. Thanks for your post.

Glad I could help and let us know how the new tuning fork is working.