Interesting little robot. It seems like you are developing an eye toward "what can I use for robotics" when it comes to looking at things; while the use of metal tie plates for robotics isn't new, it does take a certain amount of insight until you get that "aha!" moment, then you start looking at everything like that (hmm - can I use that watermelon for a robot part? /joking - or am I?).
Regarding your tip about lubricating drill bits with oil: Yes, this is paramount. In fact, there exist special purpose oils just for the task called "cutting lubricants". On a per ounce basis, though, they don't come cheap. The best oil to use, one recommended by tons of old-time machinists stretching back decades or more - is common bacon grease! It doesn't matter if it is rancid or not. Save it up, put it in a small jar and stick it in your fridge (maybe with a warning sticker). Dab it out as needed. Best part: As it warms up, you get the wonderful smell of bacon suffusing your shop - what could be better?
/note: If you're a vegetarian or vegan, then you might be SOL on the bacon grease...