End Pin Adjustment

...Tap downward to hear end pin tap tone. Remove material evenly around this rim to lower frequency to (242) Hz goal frequency, if too high before.
Remove material from the back side (end) of the end pin, to lower the horizontal tap tone to (227 1/2) HZ if too high now.
..Once this is at (227 1/2) HZ, the downward tap on the head should then be at (242) HZ.

...This acoustical agreement is important for the tone of the instrument to be clear. When the end pin tap tones is 'off', the tone may sound 'garbled', like radio static when a station is not coming in clearly. or the tone may 'break' when playing loudly. We want the vertically downward tap tone of the end pin to be (242) HZ and the end (horizontal) Tap Tone be (227 1/2) Hz . Notice that when you tune one direction to the goal Tap Tone frequency, the other automatically moves closer to its desired tap tone goal.
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...The adjustment is 'simple'.
... If the downward end pin tap tone is too low (compared to (242) HZ; tap downward from above to hear the frequency) then you need not remove the end pin from the instrument, simply cover the varnished surfaces on the back of the violin with lightly applied masking tape, to protect the varnish, and then file or sand the back side if the head, probably with a small sanding stick, while maintaining the overall original shape profile, (on its outside back surface) to bring the tone up to a perfect match with (242) HZ, downward tap tone.
..At this time, check the tap tone horizontally against the head of the end pin. It should produce an end tap tone of (227 1/2) HZ.
..You can polish the end of the end pin with a piece of leather or canvas ( or what ever works best for you) to bring the wood back to a shine.
...I imagine that you will be surprised how much difference these adjustment can make!
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...If however, the downward side tap of the end pin is too high,
we will lower this by sanding the perimeter of the head of the end pin, evenly all around until this tap tone drops to (242) HZ goal:
...Again cover the surrounding surfaces with blue tape, and using a file or sanding board, (or for removal of larger amounts I sometimes use a Dremel tool with a small sanding drum to sand around the perimeter).
... Just a small amount of material removal makes a significant change in tap tone frequency so take small steps and check the tap tone frequently .The horizontal tap tone of the end pin should be at (227 1/2) HZ. {(242) HZ downward and (227 1/2) HZ horizontally.}
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(Modified 2/2022
(Page AA-9))

End Pin Adjustment for best tone and performance...

...Listen to the comparison to the downward tap of the end pin (pretend that one is done with the left hand and the other with the right... it is hard to show correctly when the camera is in one hand).

...If the end pin side tap is too low, then sand the outer end until the side tap frequency comes up 242 HZ frequency. Constantly turn the end pin while you sand to keep it a uniform shape.
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...This is the downward tap against the side of the end pin when the end pin is in the instrument. Here it is useful to have two (identical) tapping pencils so the two tones can be heard one right after the other.

..There is a further thought you might want to adopt in your instrument making as it relates to the end pin:
..The end pin is most responsive when tapped in the direction of the wood grain. Just tap the head for different directions noting the most brilliant tap response. Turn the end pin so this direction is vertical. Now file a small mark on the bottom center so you can reference it for future removals.

End Pin in side profile, sectioned in half...