The vernier scale on my Vertex 6" RT appears incorrect. The RT is 90:1 = 4 degrees per rotation. The main scale is graduated 0-30-1-30-2-30-3-30-0, and the attached photo shows the dial 0 to 30 minutes, with the secondary marks at 10 minute intervals and the individual marks at 2 minute intervals. The vernier is marked 60-0-60, which I take to be +/- 60 seconds from 0, or 2 minutes long, the same as the main scale individual marks. So, the vernier should span from one individual mark to another, but it appears too long, or too short. The photo does not lie, the vernier 60 mark is aligned with 0 on the left, and the 60 mark on the right floating between primary marks, with a span of about 11 1/3 primary marks. It seems to me that the vernier should span a number of marks divisible by 6 (or 3), with the obvious candidate being 12 primary marks. Then any vernier mark aligning with a primary mark would denote a multiple of 10 seconds, with interpolation to 5 seconds possible. Which is crazy, me or the vernier ? This subject comes up because I am using the RT to mill out a 6-way splined bush with some critical fit requirements. If the vernier is wrong, what about the rest of it ? How can I check that a 60 degrees step is always 60 ? John.