I've never cut delrin but I've cut high quality HDPE. As others have stated it cuts like buter.
Using a 0.25" 2 flute upward spiral bit at ~10000rpm I cut at 50ipm taking 0.125" per pass with excellent results. I'm sure I can cut faster.
Wouldn't HDPE be a more suitable material to cut bearing blocks with? About 1/4 of the price of delrin with good tensile strength. Easily can handle the work of bring a bearing block even in lower grades.