Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
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Preferred Drill Bit for G90
What type Drill Bit is best with 0.050 thick, G90 Lock Forming Galvanized Steel? I am using a HSS Black Oxide 5/32" bit to drill thru masonry brackets for installing windows. The bits dull after 2 or 3 brackets.
HJ HuguesInstaller - Ripley, Tennessee, USA
August 31, 2011
Hi, HJ.
My belief is that the galvanizing is soft and relatively thin, and it is the steel that consumes the drill. Black oxide is an extremely thin aesthetic coating and has little to do with the issue either. While titanium nitride coated (gold color) drill bits might be a little better, I think the drills are not hard enough for the steel you are drilling. Use a bit of cutting oil, or even water, if you can.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
August 31, 2011
Black oxide is normally used on the cheapest bits. High speed steel bits is a minimum and that may be with or without a coating.
For bit life, try a couple of sets of cobalt steel bits. They cost a bit more but will last longer and cut faster, thus saving you money.
They can be resharpened with a big end sharpener from your local big box store.
Solid carbide is the ultimate, but they break easily unless you are using a drill press. They also need resharpening which requires a diamond sharpening unit.
As Ted says, try cutting fluid. It really helps. Tap Magic is a common one. They have one for steel and one for aluminum.
Plain vegetable oil Crisco) cut 50-50 with rubbing alcohol works very well, but takes a bit more cleaning.
- Navarre, Florida
September 1, 2011
James is right, cobalt bits are the way to go and they can be sharpened on just about any grinding wheel although white is the best. Just a hint. HSS tool steel blues very poorly and takes on a greyish frosty finish not dark black. If your drill bits are indeed midnight black then you can lay odds that the material is carbon steel and not HSS steel. Carbon steel bits would explain the poor performance that you are getting as well. I think you will find that if you purchase some good quality Dormer, Milwaukee or Norseman HSS drills your longevity will go up a lot. But, if you are making a living with those drills I would still go to cobalt and I would buy high quality ones as well.
Rod Henrickson
gunsmith - Edmonton, Alberta, Canada
September 2, 2011
September 2, 2011
Actually James, now that I'm thinking about it, the old bunny humpin', hybrid driving, ecofriendly freak recipe is Common dish soap, vegetable oil and water. The dish soap suspends the oil in the water. It actually works quite well as a lubricant and coolant and cleans up with water. Oddly enough its not far off from the machine shop coolant of old which was animal fat, sodium hydroxide, calcium and water. Except this new recipe is better because no animals are killed to make it. Just Canola plants. (Rapeseed) is no longer politically correct to use or say. LMAOROF And now you know!
Rod Henrickson
gunsmith - Edmonton, Alberta, Canada
September 6, 2011
Canola is a trademarked name for a particular hybrid of rapeseed. I don't think it's politically incorrect to call the plant by its correct name, but it might be offensive to victims to get a grammar school snigger from the opportunity :-)
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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