No there is no adjustment. But your method of testing is not ideal, really you need to set up a test piece between centres and turn each end then measure to see what the difference in diameter is, this will eliminate any runout in the chucks.

Have a look at Mechmans recent post part way down the page in this thread about how to do it

J

Both headstock and tailstock are located/clamped onto the v bed.

Hence if there is a mis-alignment it might be bad news. However I cannot imagine it is possible for the unimat to abuse it self to this extent, so short of dropping on to a hard surface not likely.

I would not think that the error described is normal and would cause difficulty (unimat3's were made in a proper factory! and when I bought mine over thirty years ago were quite pricey)

The sockets on the unimat are (more or less parallel) and my experience was that they did loosen after a lot of use and I made fractionally larger replacements.

I think other respondents are right in that it is the holding arrangments at either end that are to blame, and as Ian says use pointy bits to make a judgment.

John