7.1 Introduction
Tim A. Bacon
Keep your fingers away from anything moving, at least the ones you want to keep…
Saws are used frequently in machining and while they are very useful tools, they present severe risks to machinists. To stay safe, know the risks, and follow recommendations to protect yourself. Here are some general guidelines to keep you safe when using saws.
- Keep your hands and fingers away from the blades until everything has stopped moving, and not before.
- Do not wear gloves. Although the part may get hot, and wearing gloves may seem like a good idea, do not do it! Gloves can get caught in the blade and pull your hand and fingers into the saw. If you need gloves to clean up, make sure that none of the equipment is running while you clean.
- On the vertical bandsaw, use something other than fingers when pushing material through the saw. Keeping your fingers away from the blade is a good way of ensuring that you will still have them at the end of the day. A good alternative to fingers is a stick of wood for pushing parts into the blade.
- When making cuts on a vertical bandsaw and the blade gets stuck, it might be tempting to pull back on the part instead of pushing straight through. The hazard with this approach is that if the material catches the saw blade, it will pull the blade off of the track and possibly damage it.
- The three tooth rule says that the thickness of the material being cut needs to be at least as thick as the distance across three teeth. If less than three teeth are engaged in the part, try stacking parts to make the material thicker. Another option would be to place the part on top of a scrap piece of material to increase the number of teeth that are cutting. See section on saw operations for more detail.
Similar to the three tooth rule for thickness, the RPM (speed) of the saw needs to be considered. In general, use a fine-tooth blade with a slow rpm for steels, and a coarse blade with a high rpm for aluminum.
A chip is a splinter of material that comes off of a larger piece of material being cut. There is a more detailed discussion of types of chips in the chapter on general machine shop safety. Two things need to be present to make a chip: Heat and pressure. The heat comes from the saw moving over the top of the part, and the pressure comes from the force applied to push the blade into the part. In some cases, the part is pushed into the blade.
One of the first operations in the machining process is to saw material down to a size slightly larger than the finished part. This smaller piece of material is referred to as the stock. Consideration of how the stock will be held during machining and the cost of the material will dictate the final stock size. If the material comes into the shop in long lengths of bars, it is cut up on the horizontal bandsaw. If the material is smaller in size and can be readily handled, it is cut on the vertical bandsaw. If the material has been hardened, it may be necessary to use