From Team 449 Wiki
Layup (sometimes called laying up, layout, or marking out) is the process of marking a design onto the workpiece . On our team, this usually means marking where to cut and drill on a piece of metal.
Reasons for layup
Layup techniques allow us to machine to much tighter tolerances than with our previous methods, with were either marking with Sharpie or marking on masking tape with a pencil. Both of these methods are highly inaccurate, which often lead to poor-quality parts.
The basic idea
In our layup process, we use scribes to mark on the metal. The advantage of this is that because the scribe actually scratches the metal, the intersection of two scribed lines can be felt with a center punch. This is a much more precise method of hole placement than by sight, as it is quite difficult to get the tip of the punch exactly on the center of two inked lines.
- Get a dimensioned drawing of the pattern you want to mark.
- Use a Magnum Sharpie to put black ink on the general area where you will be marking. This will make the scribe marks visible.
- Time to start actually measuring dimensions. Use calipers to scribe lines at the correct distance from a known line (e.g. the edge of the workpiece). To do this:
- Set the calipers to the right distance.
- Tighten the locking screw to keep the calipers at this distance.
- Place one of the tips on the workpiece, and the other one on the edge/line that you're using as a reference point. It should only just be over the edge.
- Slowly slide the calipers along the edge to scribe your line.
- Holes should be at the intersection of two lines. To center punch:
- Place the tip of the punch in one of the scribed lines.
- Slide the punch in the line until you feel a dip that looks like it's at the intersection of the two lines.
- Keeping the punch in the dip, pivot it so it's perpendicular to the surface of the workpiece.
- Strike the top of the punch with a mallet or hammer.
Sometimes, a caliper may not be long enough for the distance you need to mark. In this case, a metal ruler may be used. The trick to making lines with a metal ruler is to make a V-shaped mark with the tip at the correct distance, and then to use a tri-square and scribe to mark a line through the tip.