Which set of drills to use as brass/plastics only set?

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May 30, 2016
Hi there!

Ive got a few different set of drills.
I have a nice set (Cleeline) of Fractionals, Letter, and Number set which I'll keep as is for general use in aluminum/steel.

I'm looking to modify a set of fractional drills for use in only plastic and brass. I have a spare set of cleelines, or I can pick up a cheap set of fractionals for $30.
If im looking to make a set for brass/plastics, should I go ahead and modify my set of super nice cleelines? or should I just go get and modify a cheaper set of drills?

I'm not concerned with the job of modification itself, that will be fairly easy for me.
I actually already have a modified set of cleelines too, but im looking to make another brass/plastics set so i can have two, one to work in the garage and one to work in the house upstairs.

So given that I only have one spare set of nice drills, should I "use" these up to make a brass set, or so should I go ahead and purchase a cheaper set of drills, and save this set of cleelines for the future?

I suppose the real question is, when drilling with modified drills, how important is the drill bit quality?
i do notice a huge difference in drilling quality when cutting alu/steel with cheap bits VS with cleelines, but will the difference be as drastic when comparing two modified sets (one cheap and one being cleeline)? since the bits are scraping more than cutting?


T Bredehoft

Active User
H-M Supporter - Gold Member ($25)
Dec 27, 2014
Since quality drills are needed for difficult or accurate work, I'd save the 'good' ones, and modify some "not so good" ones for brass and plastic. Plastic certainly doesn't need quality drills, just sharp ones.


H-M Supporter - Gold Member
H-M Supporter - Gold Member ($25)
Nov 9, 2015
should I go ahead and modify my set of super nice cleelines? or should I just go get and modify a cheaper set of drills?
I don't have any high end drill bit sets - best I have are Chicago Letrobe. But even then I feel bad about modifying them for plastic and brass.
So I bought this cheap HFT set, and dull them on an as needed basis. So far, only 3 of the 29 have been modified.
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Jul 14, 2017
I've been thru alot of drill bits Low end, high end, and there is only one conclusion the high end is only way to go, they last way longer and make life much simpler, also the precision achieved is unmatched, good quality drill will brake before it bend now my favorite is the HSCO spiralbohrer from Guhring they are sort and sharpened by laser so they don't have have dead spot in the middle, little expensive but worth it, i'm using them with my hand drills more as they need more rpm, but for precision, i've run my lathe at its max 2000rpm on copper and got a mirror finish.
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