Incorrect speeds and feeds are a surefire way to make terrible noises, break tools, and scrap parts. Initial attempts to machine this hardened ring gear made noises that would make any machinist shudder. Through experimentation, we optimized a recipe that is reliable, leaves a great surface finish, and provides good tool life.
As covered in our 10 Things No One Tells You About Machining article, runout is everywhere! However with most tools we use this amount is negligible. Using, say, a 3/8” endmill with .0008” of TIR won’t have significant consequences (especially when roughing). Unless you’re chasing tenths, the runout is such a small percentage of the tool’s overall diameter (~0.21%) that it wont have any noticeable affects. As you small diameter tools, this percentage begins to increase. Using a 1/32” endmill with the same runout amounts to a TIR that is 2.56% (about a 10x increase!). This can result in uneven wear, chatter, bad surface finish, missing tolerances, and even broken tools.
McMaster-Carr is great for finding a part, making small orders, and even grabbing CAD models or drawings for hardware. Keep in mind however it can get expensive – if you’re buying in volume, spend the time to source your parts directly for a lower price.
You probably already know this, but tolerances are important. If your product is a standalone part with only one component, tolerances may not be as important.
ER Collets are often a go-to for machinists because collets are readily available at varying price points and allow a tool holder to hold varying size tools. ER collets also have a greater collapsing range than SK collets. However, there are a few things that aren’t readily apparent to the beginning machinist:
