Making a lathe test bar

Is that equation for a beam supported at both ends or one?
Robert
 
I use Mrpete222's method that Micri linked to. Used 2 arbors, turned them down to within 0.0004", IIRC, and used them to line up tailstock. What's nice about this method is you can position the tailstock anywhere along the bed and check your alignment.
 
I don't understand how Mr Pete's method works if your headstock and tailstock have different tapers? If you use a Morse adapter at the headstock to machine the tailstock piece don't you have and issue with runout of the adapter? Or are they precise enough that is not an issue. Why does he not machine these between centers so they are perfect?
Also a 2 collar test bar can typically be made from scrap at no cost.
Robert
 
I bought an MT5 test bar for $100 that plugs into the headstock taper. It's good for about .0002 if I remember correctly. I agree with most all that was said here but when I first set up my G4003G I needed SOMETHING I could trust to get me started.
 
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