135 degree drill bits are normally for hard metals, There are 118 degree drill bits designed for use in Aluminum that evacuate waste/chips quicker due to a high helix, they work very well on plastics/acrylics and wood, I still won't drill all the way through acrylics, but these drills eat acrylic so fast it doesn't have a chance to get hot, they also work very well for hard woods, stuff like Ipe, Maca Jatoba and wood that likes to split and blow out. Enco carries these bits in nearly any size you need,
I've never used any thing like a Drill Doctor, but I've heard they work very well; it's just that as a Machinist/Instructor, I would be subject to ridicule. But as I tell students if it works for you and does the job use it. They still have to learn to sharpen drills by hand and do split points as well.[}
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