Colleen,
What do you mean by "slanted stitching pattern"? All lock stitch machines wraps the bobbin thread around the top thread. The type of thread, tension and the weave of the fabric affects how the stitches look, sometimes a slight slant and sometimes none. To see the real stitch pattern unthread the machine and remove the bobbincase. Now sew a line on thick paper or on an index card. You should see a perfectly straight line of holes. The shows that the machine is doing it's job. Machines like the 301, 201, 66, and 221 all have the needlebar enclosed in a bushing or casting meaning that the bar can not move sideways at all so the stitches have to be straight.They just don't always look it. The needlebar does only one thing. It goes up and down.
I hope that was clearer than mud,
Cathy