Re: maker of small drill bits (#78, #80) for hand drilling resin kits


Owen Thorne - owen at udel.edu
 

I have enjoyed this discussion, but one question remains unanswered for me. I too have had trouble finding reliable affordable bits for hand-drilling plastic and resin and I remain unsure if I should be shopping for high-speed, carbide-tipped, carbon or another. For me, skinny bits from the hobby shop or Amazon suppliers break too easily and are often dull from the start. These bits rarely last long enough to dull, maybe because I am increasingly fumble-fingered and visually challenged with age but maybe because I am choosing the wrong drill-bit material. The expensive Otto Frei and Gesswein products RJ Dial discussed above are "high-speed" so is this the correct material to choose or are those just better quality (and pricier?)

I agree with folks who like the style of bit that has a 1/8th inch shaft and necks down to the bit. The collar with size info is convenient. Chucking them in and out, and sizing or keeping track of loose bits is so easy. Drill Bit City bits have been pretty good lately, but they still break for me, and they are more expensive to replace.

McMaster-Carr has provided me excellent tools and materials in the past, so I trust them. They write about bit materials here: https://www.mcmaster.com/drill-bits/

Quoting from their site:


"A number of factors determine which drill bit will be best for an application, including the type of material to be drilled, drilling speed, and desired number of holes per bit. Select a drill bit with the combination of material, finish, length, and style that will be best-suited for your job.


“Material

  • High-speed steel bits are for general purpose drilling in most material.
  • Cobalt steel bits have better heat and wear resistance than high-speed steel bits, so they can run up to 25% faster and have a longer tool life.
  • Carbide-tipped bits are more wear resistant than high-speed steel and cobalt steel bits, so they maintain their sharp edges longer for excellent performance on abrasive material, such as plastic. Because they aren't as brittle as solid carbide bits, they can be used in less rigid setups, such as a hand-held drill.
  • Carbide bits are harder, stronger, and more wear resistant than high-speed steel, cobalt steel, and carbide-tipped bits for the highest accuracy and longest tool life. They retain a sharp, hard edge at high temperatures for the best performance on hard and abrasive material. Made of solid carbide, these bits require rigid toolholding to prevent breakage and should not be used in hand-held drilling applications."

So, while choosing high-speed bits for hand-drilling plastic and resin seems counterintuitive, the commonly available carbide bits are specifically NOT recommended, as per above. Does anyone have experience with cobalt or carbon-tipped bits? Or is there another material, tip shape, angle, or coating we should be using for resin or plastic?

p.s. One key for me is lubrication, as Curt Fortenberry mentions above. I keep a hunk of beeswax on the bench and poke the bit into it each time I start a hole or clear the chips. And as Hudson suggests above, chucking the skinny bits really short also helps prevent breakage while using a smaller, finer pin vise has helped me to avoid lateral stresses that can break a bit.

Thank you, all,

--
T. Owen Thorne
Cecil County MD USA
owen at udel dot edu

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