Delrin is the best plastic I've worked with so far as far as not melting on you, its pretty damn rigid, so its pretty decent to hold, you can get some fantastic surface finishes off of it.
However it is still plastic.
I've run into the birds nest problem and the chips deburring the hole for me on many materials. Generally, feed it harder for a stiffer chip that will hopefully break and fly off, and
peck more.
Remember this is plastic, its almost as easy to drill as wood. No matter how heavy your chip is, its not going to break, so feed it hard, really hard (remember its just plastic), and peck often
to break the chips. You can run a chip break cycle that only pulls back a few thou, I doubt with that small of a drill you have enough revs to melt things up, so pulling all the way out
isn't really necessary, up to a certain depth ratio. <-- I don't know what it is.
In nylon, .25 inch holes, I'd feed .010 to .016 a rev, and do a chip break every .050 to not tear up the opening of the hole. It would sound more like a jack hammer than a drilling
cycle, but it worked, and relatively quick.
Going 12 or more X deep, you will most likely have to pull out to get the chips to clear, I wasn't going that deep.
Either way, you have to break the chip so it doesn't birds nest around the tool or swing and create its own chamfer.