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Drill 4.8mm SS 440a 60HRC to 4.9 with Cobalt Steel bit?

arash

Plastic
Joined
Oct 7, 2022
Hello all,
I need to make an oblique hole on an instrument larger than 0.1mm. it is already 4.8mm and I need to make it 4.9mm. I have got two types of drill bits one cobalt steel and the other one HSS black and gold oxide coated. The part is SS 440 and hardened to 56HRC. I am trying not to damage the instrument and I need to get different opinions before doing anything. Would it be feasible to do it, I have 2500RPM DeWalt and some battery-operated drills.

Thank you,
 
Would it be feasible to do it
No......................not with a hand drill.............not with cobalt or HSS...............or even a carbide drill for that matter. Oblique? Drill at an angle on a flat surface? Drilling a hole larger in harden material is a non starter..............milling yes, drilling prolly not.

Bring it to a shop and ask them for help..............
 
Your playing with fire by even considering it..........

with a hand drill and steel drill bits of any grade.....

Carbide only for sure, and definitely only on a drill press or mill, and even then everything will have to be juuuuust right.
 
If you're doing it by hand (can't fit it in a real mill or lathe), the best way is likely abrasive machining it (coarse hone), like a 1/8" dowel with 180 wet-or-dry paper wrapped tightly around it. Will be tedious but doable with minimal damage, but with some edge rounding at entry/exit.

How long is the hole? If short, ocilate dowel/paper back and forth, if long you'll have to stroke whatever lenght is needed, but plan on having to swap fresh paper in multiple times.
 
Only taking out .1mm sounds like a reamer job, if you can find one that will do that hard of material. Otherwise as others have said, abrasives.

Ed.
 








 
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