PROJECT 2: Cutting the Armor Pieces

Cutting metal and plastic plates are essential skills for the robot builder, so we're starting there first. This project will get you working with the circular saw, jigsaw, and miter saw by cutting the armor and frame pieces for the project robot. While all of these cuts could be done with the jigsaw, I'll demonstrate some with the other two tools to show situations where their specialized designs allow you to make the cuts more quickly and precisely.

Caution: Eye and ear protection are mandatory for these tools. They are incredibly loud, and pieces of metal will be flying everywhere. Review all of the general power-tool safety protocols described in Chapter 5 of Kickin' Bot, as well as the sections that correspond to the specific tools used below.

Part 3: Cutting Lexan Side Pieces

The sides will be made out of 1/2-inch polycarbonate. They should measure 14" x 3.5". Since I have a 24" x 24" sheet, I will be cutting 3.5-inch wide strips off of the sheet for the parts, and then cutting those down to the correct length of 14 inches. Cutting the sides to the correct length can be done with the jigsaw or circular saw, although the best tool to use in this case is the miter saw. Again, this saw should be fitted with a non-ferrous metal-cutting blade (which is usually also good for plastics)., as described in Chapter 5.

click on an image to enlarge it

One important difference with this setup is which piece the waste will be. In the previous cutting operations, we removed a smaller waste piece from a larger sheet. When cutting the side plates, you will be cutting off the part you want from the sheet, not the waste. That means that you've got to measure your offset from the edge of the base to the far side of the blade, which includes the thickness of the kerf. If you use the same offset as before for your guide, your pieces will be shorter by the thickness of the kerf. At the end of this operation, you should have four strips that are 24" x 3.5".

You can see here that the edge produced by the circular saw is very good, and requires little cleanup. At the bottom right edge of the piece is a little stub left over from the cutting process that will need to be sanded off. 

Use the disc sander to remove the little stub mentioned in the previous step. Carefully bring the edge into contact with the abrasvie surface. You only want to remove the stub so that the surface is flat overall.

Mark off a 14" line on the Lexan side panel, carefully indicating the waste side. Clamp the piece to the saw, making sure to line up the blade with the kerf on the waste side of the cut line. The most important thing is that the work remains flat in the area around the blade. Do whatever you have to on the clamp side to make sure that the stock is flat on the table near the blade. To speed up operations, you can set up a stop block. That way, you won't have to measure, mark, and line up all the pieces. After setting it up on the first piece, the stop block takes care of aligning all the rest of the pieces to the right length. Make sure that the stop block and clamp are on the same side. If they are on opposite sides, the blade may bind and throw the piece, which can cause injury.
  Making sure that you have adequate lubrication, start the saw with the blade covered and not in contact with the workpiece. Allow the blade to spin up to full speed, and slowly bring it into contact with the workpiece. Let the saw dictate how fast it wants to cut. Keep your motion smooth and slow. Continue all the way though the part and release the trigger, keep the saw held down until it comes to a stop, and then retract it. You should now have a 3/16" thick aluminum baseplate measuring 15" x 14", and a 1/4" thick Lexan plate also measuring 15" x 14". You should also have four 1/2" thick Lexan plates measuring 14" x 3.5" each.