Tips for Accurate Measuring and Machining

[AmiableVariable]

As mentioned above, for a lot of layout, a good square, a sharp pencil, fine tip sharpie or scribe and layout die, and ruler are your best friends. Height gages are also incredibly helpful, though do make sure that the surface being marked is perpendicular to the surface the height gauge is resting on. Tape measures are usually better for longer pieces. Also, thinner layout lines and marks allow for higher precision.

First off, make sure everyone manufacturing parts remembers to consistently zero calipers and measure from zero on the rulers, not the end.

Regardless of which tools you get: Pick your battles, and be sure you have the best (least variation) possible reference points.

For example, it's less precise to use a rough cut edge (cut with bandsaw or hacksaw) as a reference point to mark out holes, because it gives an uneven starting point. It would be better to mark a straight line that is perpendicular to a trustworthy side (or a set of perpendicular lines, if everything is rough cut) and measure the distances from that. If this is done before the final cut of the shape, you could later use those reference lines to cut the final edges.

When drilling holes to mount parts like a versa-planetary, mark the center for where the shaft is going to go first, because that is typically going to be the most important part relative to the rest of the design. Then, mark up the centers for the rest of the mounting holes relative to the critical center-point, not from the edges of the part. Unless it's a very compact design, having a slight rotation in the motor mount should cause a less trouble than an incorrect distance between mounting holes. If the rotational alignment is important, pick the two most important points on the piece (or the two that are the furthest apart) and measure those first.

When actually drilling hole, center punches and pilot drills help. In regards to cutting pieces, the thinner a line you can give machinists to follow, the better. Additionally, mark which side of the line you would rather have them err on. If you need a smoother line right at the mark, cutting a little large and filing the part down to the line is always an option.

Hope this helps!