Take a piece of any stock that "has not" been edge jointed
at all. Run the stock through the jointer "several" times
and then measure with a accurate tool(calipers).

By doing it "several times", yes, you will possibly accumulate error that
can be measured with a caliper. I think the OP is seeing taper with out
using a caliper.

If you start with parallel faces you should end up with parallel faces. If
you start with a taper you should end up with a taper.



In my opinion, you "will" have taper to some degree. I have
a highly tuned, well adjusted DJ-20 and I know it will taper
a board in a heart beat. It has since the day I got it.

A jointers function is to "face plane" stock and to do some
edge work.

Stoutman wrote:

Keep in mind also that a "slight" taper result is common on all jointers.


Not on mine.


Jointers are not used to create parallel surfaces, only straight and flat
surfaces. The TS should be used to make the opposite edge smooth and
parallel.


Only to take it out of parallel at the jointer??