Hey! I love it when work overlaps my hobby!
I have had some experience with the deep drilling and Machine tool customers at work. Feel free to PM me if you have questions, I'll try to share some practical experience that will save some money and improve results.
I have had some success selling these Magnetic filters to prolong the life of the high pressure filters, And remove some of the finer metallic particles without removing the lubricating properties of the oils.
Magnom Case Study: Gun Drilling Machine -
When filtering the cutting fluids used in this process, keep your micron rating above ~10um to prevent filtering out the larger sulfur and fatty acids commonly found in these oils. I would also recommend a series filtering arrangement with progressive filtration to minimize the annual cost of the consumables. There are a number of commercial products available which will duplicate the (impressive) arrangement that Chad machined for his filters.
The big machine tool guys will also try to maintain their oil temp to within a few degree's of ambient temp to control expansion and tolerance consistency. They do it with expensive chillers, however there are some commercial products that will do a good enough job for smaller operations.