Thanks! I do have an SR. I'm confused because everything I have read says go "slow". But, after being frustrated, I did go faster and it didn't seem to make any difference. I haven't seen a speed control. I'll have to look into it.
Drilling Speed and Pressure
To maximize the life of your drill and minimize material damage, it is important to run your drills at the proper drill speed and pressure. Drilling speeds vary with diameter of diamond drill, diamond mesh size, coolant being used, drill wall thickness, diamond bond type and hardness, as well as material hardness. Micro Diamond Drills from .001" required drilling speeds as high as 150,000+ RPM. Whereas very large diamond drills 48" diameter require drilling speeds as low as 3 RPM's.
Small Diameter Drills
Small diameter diamond drills must be used at significantly higher speeds than larger size drills. It has been found that higher Revolutions Per Minute (RPM's) improve surface finish and overall drilling performance. RPM's for diamond solid drills .001" to 2.5mm (without center hole for coolant flow capabilities) range from 9,000 to 450,000. Drilling equipment that can accommodate these speeds include: high speed air spindles, hand held drills, and other specialty micro drilling equipment. High speed air spindles can run up to 450,000 RPM, hand held drilling machines to 35,000 RPM, and specialty micro drilling equipment up to 25,000 RPM.
Also, the old adage that you get what you pay for is (usually) accurate. I tried the twist drills recommended by another RTH'er and was disappointed with their performance life drilling 1.5mm and 2.5mm holes. So, I'm going the opposite way and buying some solid (not twist) electroplated drill bits that are triple-coated with diamonds. $24.99/pack of 6 ($4.165 ea). As soon as I can, I'll post my results.
Specs for the drills I'm buying:Recommended Operating Speed: 7,000-10,000
Maximum Operating Speed: 30,000.
USED ON: High Speed Drill Press, Mounted Hand Piece Drill (such as: Foredom & Dremel), High Speed Air Spindles.
APPLICATION: drilling smooth and clean holes in a wide variety of:
ceramic, tile & related materials
advanced ceramics
glass & quartz
optical materials
composites
natural & synthetic stone
semi-precious & precious stone
many other materials
I spend weeks and weeks tumbling my amethyst and other stones and I hate to ruin them in the end.
Peace,
James