I'm by no means a good machinist. I get along OK, and I can perform most of the tasks that I need to on my own; but I still need a lot of help to get things done and done well. I'm quite thankful to Steve, the machinist here at CC, for teaching me through this semester and helping me to fabricate the parts needed for my arm project and I hope to learn much more from him. With that in mind, I thought that it might be helpful for other beginning machinists to have a resource for basic machining techniques that are not very complicated so they can get started. The best resource I've found is by far the video series on prototype machining provided by MIT here, but I hope I can help with some other tips and tricks I've found useful.
1. Zeros Are Easy
When you are working on a part with a pattern-based set of features around a known location or line of symmetry (rings of holes or lines of pockets are a good example), it can be very helpful to set your digital read out or dials to zero at that location. When cutting on a lathe, avoid mistakes by moving to the depth of cut you want and setting to zero. Zeros are far easier to remember in general than 4 or more digits! Of course, if there are multiple features you want to make in a part that are not all around the same location, be sure to be keep track of where you are in relation to a common reference point.
2. Notes Are Your Friend
Keeping good, easy to read notes handy is a good way to avoid mistakes. I keep a notepad near me at all times in the shop in case I need to write down coordinates or annotations regarding the part. That said, make sure you keep your notes organized and easy to read at a glance; if you need to reference them to double check a cut, you need to be right the first time.
3. Visualize The Sequence
This is a skill that is extremely important to have when designing parts for manufacture, and it is impossible to fabricate parts without it. When designing parts, adding a machining sequence as a note in the drawing or annotations (if permitted) can help to clarify design intent. Mentally walking through the machining sequence before making a single cut will help to ensure that the tools necessary are available, that the material to be cut is of the correct dimensions and type, and that sequence-dependent operations are performed in order. Before making each cut, ensure that you are certain about the direction of travel of the part and cutting tool and that the tool will remove the material desired and no more. Spending five to ten seconds visualizing the sequence can save you hours of rework from scrapping a part.
4. If In Doubt, Ask
There are a ton of resources available for the machinist to reference. "Machinery's Handbook" in particular is a valuable resource for almost every operation in the shop, from A-Z. Of course, if you are not a beginning machinist like me, you won't necessarily have the knowledge needed to fully utilize it. If you are lucky enough to have someone more experienced around, ask them for advice if you are unsure of the details of a particular operation. However, be cautious of amateur advice; it can be extremely dangerous to undertake an operation with false certainty.
5. Be Cautious
Machine tools are extremely powerful and can be quite dangerous if you are not aware of your surroundings. Beyond the simple safety tips such as avoiding moving parts, be sure you think through what will happen if the operation were to go awry. In particular, be cautious of possible projectiles. A disk being turned on a lathe can become a flying saw blade if it catches on the cutting tool. Stand to the side of the workpiece when using a lathe, if possible; ensure that the workpiece is well secured! Make sure you won't be caught on moving machinery and pulled into cutting areas! Do not cut wire on bandsaws! (A girl at my college was seriously injured doing so). Double check feed speeds, cutting speeds, tooling, collet tightening, coolant, chip removal, workpiece holding, etc. before starting any machine. Think of the forces involved and where torques and forces are applied; where rotations may occur; where translations will occur; where frictional heating can cause normally safe surfaces to become dangerous. Always wear eye protection.
Hopefully, these tips were helpful! I'll add more in the near future, but for now be safe and enjoy your newfound endeavor!