Setting out an angle on the mill table so that I can machine a set of gears at 9.5°. I know lots who will now be screaming at me to use a sine bar.
It might be easiest to start with the simple right angle triangle. Below we see the triangle with the 9.5° angle, the adjacent and opposite sides.
This is then back to the simple rules:
tan(9.5°) = opposite / adjacent
The base of the triangle is best if it is close to the full width of the table, with a bit of space to allow for it to be marked. This distance is 92mm. Hence the length of the adjacent is 92mm. We can then rearrange the equation to calculate the length of the opposite side:
92mm x tan(9.5°) = opposite
opposite = 15.396mm
I used a permanent marker to create an area on the table.
Then using a mild steel pointer in the spindle I marked an origin at one edge, bottom of the photo.
I dragged the pointer on the table with a light pressure being held on the spindle scroll. Try and avoid scoring the table permanently if possible.
The centre of this origin is X = 0mm, Y = 0mm on the DRO or dials.
I then moved 92mm in Y across the table width, here I marked another cross for reference.
The X was then moved 15.395mm and I made another cross.
Then I used a ruler to line up this point with the origin and lightly I marked through the permanent marker.
You can mark this out using the dials on the X and Y axis of the milling machine table. However, this is really easy with a DRO.
Finally here I am aligning the rotary table to this line that is at 9.5° to the Y-axis. Nearly ready now to cut those bevels.