Hi, I'm trying to tram my X2 mill. I took a machining course where we layed a ground piece of steel on top of the table and then swept that plate with an indicator. I don't have a surface plate so I was wondering,
What do you use as a reference surface when tramming your mill?
I read an article in HSM where a brake disc was suggested but I don't have access to a surface grinder? Any ideas?

Thanks in advance.