When filing in a lathe, don't hold the file rigid, but use a slight gliding motion. This will help the file clear itself and also prevent ridges. When filing metal, vary the speed according to metal. Generally use 150 surface feet per minute for cast iron; 175 for annealed tool steel; 350 for machinery steel, and 500 for soft yellow brass. Also, don't run your hand over the work. Resulting oil and moisture will make it harder for the file to take hold.
When going to buy lumber, eliminate the guesswork by taking along the right gear. Take a good flashlight to be able to see wood in dark lumber sheds, plus a pocket knife to scrape rough-sawn boards to check grain. Also take along a good measuring tape, small square, pencil, notebook, and a pocket calculator if you will need to do much figuring.