Very much a plus one one for the Long Island Indicator site and the information they freely provide. I've always found their website to be 100% correct, unbiased, and very factual, and I certainly wouldn't hesitate to ship anything I own to them for repair. That's my number one site I use when deciding on any purchase of new metrology equipment.
And another plus one on buying the best you can afford. Some of the Chinese equipment can be ok, but if the one you end up with won't repeat? Then it's pretty well a useless paperweight. I usually buy Mitutoyo or Starrett so have really no experience with any other brands. But none of the top manufacturers make inaccurate equipment. So any of them should be good. Some are just a bit better at some jobs than others.
For the metric minded? Please use your own versions of the following. I think and work in imperial.
You can't really expect one type of dial indicator to do everything needed. There's Dial Indicators (D.I.'s) for short. There normally .001 reading with either a 1/2" or the more usual 1" travel on the indicators spindle. For that reason you want to make sure to buy an indicator with a secondary dial that shows each .100 thou of the indicators movement, at one time it seems it was more common to produce indicators without that secondary dial than it is today. But with that and the main indicator dial, your good to within + - .001 on very good indicators. Most of them will repeat far better than that, but the various manufacturers will only state their equipment will repeat within that + - .001
But you also need when you can afford it, at least one model of a Dial Test Indicator (D.T.I.) for short. While I guess they can be bought as .001 reading indicators, most seem to be and I think it's worthwhile to buy a .0001 reading indicator. Due to the design of most DTI's, they will reach in and are capable of running checks and setups in places where it would be impossible for the standard D.I.'s to do so. Most of the .0001 reading DTI's have around .030 or maybe a bit more of measurement range. But due to the actual mechanical design most DTI's use, they just aren't accurate for the linear measurements over that .030 range. That's not a fault of the indicators, it's just a mechanical design issue that relates to the linkage from the probe tip to what the actual needle deflection shows. So in use, DTI's are normally considered a "null" or zero setting indicator. By that I mean your trying to set up your part, tool, or machine with the lowest possible deflection showing on the DTI's needle.
There's probably no single magnetic base system that will work for every setup either. Even the cheap ones will work with the base sitting on flat horizontal steel or cast surface. But it's when you need to set that base at other than horizontal when you need the very good quality and strong magnetic attraction. Having that magnetic base pull away from your surface and crashing your expensive DI's or DTI's make those cheap magnetic bases very very expensive. And I do own those cheap $25.00 ones, and the $150 Mitutoyo and Starrett models. There is a vast difference in holding power for the money. But I make a point of pulling on the magnetic base after setting it up as a trial of just how strong the base is attached to the surface just so I don't get any of those very expensive crashing noises. Please don't ask how I know to do this now.
I've heard but have no experience yet that Noga magnetic bases are generally considered to be just about the best.
But whatever you buy, you will one way or another end up machining extra parts for various methods of holding and placing your indicators at the correct orientation. That's just part of owning them. Sometimes even the magnetic bases just won't work on some setups for various reasons.
And I'd very much agree about treating them as a very delicate tool that needs to be respected and kept as much as possible away from the usual swarf and crud in any shop. Good indicators are worth every penny of what they cost. DON'T ever oil them without a lot of further research first. You will do it wrong if you don't. I hope some of this helps.
Pete