by sansbury » Wed Apr 27, 2011 4:57 pm
1. You're doing really really well to get that long a life out of 1/16" bits. In general, you want to use the largest possible tool, as larger tool = more rigidity. Rigidity is largely a function of cross-section, which increases as a square of diameter. A 1/16 bit has a cross-section area of .003", while a 1/8" bit has .012" and a 1/4 one has .049. So the 1/8 bit is only twice as wide but 4 times as thick and consequently very roughly four times stiffer.
2. After tool diameter, the easiest way to increase stiffness is to use the shortest possible tool. If you hold a pencil at the ends you can snap it easily, hold your fingers one pencil-width apart and it's very difficult. Cutting your tool stickout length in half will get you a lot more rigidity.
3. >2 flute tools are mostly for metal, no? Even aluminum usually is done with 2 or 3 flute mills unless you're talking larger (like 1/2" or more) tools. More flutes = more rigidity but also provide less room for chip clearance. IIRC the plastic shop I work with usually uses single-flute bits on their routers. You can get these at MSC and other industrial suppliers.
4. For fixturing flat sheets, I love double-sided carpet tape, which has a sticking force of like 40 pounds per square inch. Even works on aluminum plate and sheet steel if you're careful, and is awesome for softer stuff. For sacrificial boards, masonite is cheap, and another great source of material are cutting boards from a restaurant supply company. They usually carry HDPE in a variety of sizes and thicknesses and you can usually get all kinds of material pretty cheaply.