My biased, but totally correct suggestions:
NO caliper, dial or digital, reads to .0001. (most digital calipers have displays to .0005, but that is their max resolution (they round to the nearest half a thousandth). Yes, you can sometimes estimate a bit closer with a good dial model, but that is not accurate enough for the case web measurement you're wanting to make. You'll need a micrometer for that.
The BEST digital caliper is the Mitutoyo Absolute. (The "Absolute" feature retains the zero setting in memory.) There are several models, mine is #CD-6"CS; bought from MSC for about $110.00. You won't be disappointed!
MSC website is www.mscdirect.com,
or phone for a catalog @ 800-645-7270. You'll have to give them the name of your 'business'--just make one up if necessary. They also have their catalog on CD-rom, which I highly reccommend--the paper catalog weighs about 12 pounds (no I'm not kidding; get the CD and save a tree!)
This is one of those tools that continually gives the satisfaction of owning the best...
I wont reccommend a mic; there are lots of good ones out there. try to find a 'friction thimble' model if you can, for a bit better 'feel'.
[This message has been edited by weegee (edited May 20, 2000).]