Tool for measuring pivot to spindle distance?

Holly,
Do you have a table/arm set-up that might differ from arm specifications, or a vintage arm of unknown mounting distance?

If you use a traditional 2 point protractor or something like a Geodisk, you don't need mounting distance. They are based on the actual location of the pivot not where it theoretically should be. If you want to use an arc protractor you need the exact distance. In that case calipers seem like a good idea.
Regards,

I've been using a straight ruler w/o sonic penalty (I think). But recently I've been thinking along your lines, Oakiris. For $40 this caliper would surely be good enough. It's allegedly good to a hundredth of a mm, but even if not exactly true, I take that it's better than eyeballing it with a ruler?

Holly has a Teres 160 table with a few upgrades. The
armboard on that table swivels and when you move it, it
changes the pivot to spindle distance. I was the one that
moved it several times when we were trying to figure out
what was wrong with her system. The armboard was very
loose, so I wasn't really to blame, (that's my story and I'm
sticking to it) :-)

I told her the first thing that she would need to do is
remeasure the pivot to spindle distance, (she knows the
correct distance), then lock down the armboard very tightly
before she installs her new cartridge. I think the armboard
loosened up over time and she hadn't used it for quite
awhile.

I think a good solid, thin metal ruler would be fine, but a
digital caliper would work too.

I have a very old original manufacture Dennesen Protractor. If I need to locate the pivot of a tonearm I want to mount, I take a piece of clean white paper and make two pen marks on it, at a distance from one to the other that is equal to the desired P2S distance. Then I set the spindle hole of the Dennesen centered on one of the two dots and line up the vertical steel pointer at the other end of the Dennesen with dot number 2. Then I lock in the Dennesen at this distance. I then place the Dennesen over the tt spindle, and the vertical steel pointer tells me where the tonearm pivot point needs to be. So, I recommend a Dennesen or Dennesen type protractor to kill 2 birds with one stone, as they say. (Because once you've mounted the tonearm, you can use the Dennesen again to set pivot to stylus distance.) Dertonearm offers an accessory attachment to his protractor, exclusively for setting P2S, but it costs several hundred dollars over and above the cost of the protractor.