Sigma 28-70 3.5-4.5 manual UC zoom lens.

Can anyone tell me how to re-set the (internal) focus on this lens? It's focusing past infinity. Thanks

If it's just a bit, it may be intentional.
Lots of zooms had over travel to compensate for thermal variances.
But. It's also possible that the infinity stop has slipped. If that's the case
it should be easy(!) The stop can sometimes be accessed under the focusing ring.
Not hard but if you haven'r done this sort of thing before, Don't fiddle with it.