Measuring a cam lobe????

I'd avoid HF and amazon for a dial indicator. Here are some from MSC: they have some so-called 'value collection' ones that are decent starters for most home-shop guys.
https://www.mscdirect.com/browse/tn...ccessories/Indicator-Base-Kits?navid=12107722

You'll find plenty of good uses for one in this work... like measuring piston to deck heights. Good investment.