Caliper?

[Dusty Chalk]

I'm thinking this one. For measuring pickups, pickup route holes, and such. Not sure it will do string gauges, one of the reviews said it was only accurate to within 0.001" rather than the stated 0.0001", but if the only difference is between a 10 and a 9 or an 11 (I have a used guitar with a Floyd Rose that I'd rather not switch the string gauges on), then I should be alright, no? And someone elsewhere recommended I get a larger one than six because one finds oneself missing a lot in that 6-8" region.

 

[DarkPenguin]

Junk. Get an iGaging.

 

[Ol'Lefty]

For strings, I use a Starrett micrometer good to .0001.

 

[shinksma]

There are cheaper versions similar to the one you linked available, and I think they are probably just as accurate. I have this one, about $12:

http://www.amazon.com/gp/product/B0002JFMIO

It works well enough for me.

If I needed something more accurate and precise, I'd pay more, but I didn't. I cannot comment on the iGaging brand - they don't seem any different from any of the other brands out there that look pretty well identical, but maybe DarkPenguin has had some good experiences with them.

 

[DarkPenguin]

It isn't. It has a few better features. It resets to 0 when you close the jaws reliably, it has a big display, it uses CR2032 batteries and it does fractions. The cheap ones like the listed one or my carrera precision tend to use and eat much more expensive watch batteries. I like the CR2032s because they also work in my clip on tuners and are amazingly cheap.

I'd definitely get the one shinksma listed over the one in the original post as it is way cheaper. But if you're willing to spend $40-50 the igaging is the way to go. After that there is quite a price jump to things like the mitutoyo.