Good drill bits

[bigtiller]

I use Cobalt bits in the drill press only. They are to hard and brittle to use in a hand motor, they'll grab and break. All my hand drilling is done with HHS bits.

And I never use bits with a reduced shank. Sometimes they can't be griped enough to prevent spinning in the chuck.

 

[Michael Aos]

I don't have a lot of experience to compare them against, but I was recently EXTREMELY impressed with these Dewalt Industrial Cobalt bits and some aerosol cutting oil from Harbor Freight.
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[marchanna]

I used to own a cutting tool manufacturing company, so I'll give you my advice. There are many grades of SS and some are much harder than others. In general HSS is not hard enough to drill SS. Cobalt and carbide are the drill types that you would need. Don't worry about coatings, they're typically just for production applications. You want 100-150 sfm for carbide and double that or more for cobalt. Sfm (surface feet per minute) πD x rpm if you're using machine tools but, otherwise about half trigger on your hand drill. A drill press is ideal, especially for carbide, but you should be able to drill straight enough for cobalt. Cutting oil or coolant is only necessary for deep holes - thicker than 1/8".

 

[shaeff]

I've only recently stumbled across proper cutting oil. Before this, I used old motor oil, 3in1, PB blast, WD-40 whatever I had on hand. The cutting oil for thicker steel really seems to make a difference. I use stuff called Tap Magic, I think Forney is the brand name.

 

[17 Oaks]

By high pressure, I mean enough force so that you are actually cutting into the metal making decent chips. I see way too many people basically letting the bit spin against the metal just work hardening the metal from the heat.

Concur

And what is slow speed in your guys books?

I look for smoke and feel for heat and watch for Chip production...

 

[SpringHollow]

Until recently, I kept my good bits for "special" projects, never wanting to ruin them for normal stuff. So naturally I never used them and used HF coated bits instead. Well, on one project with harder metal that was burning up the HF drill bits, I grabbed a used American made drill bit that I had bought in a pile of tooling. What a difference. What took minutes before took seconds. I was converted. An example of a good American made drill bit would be Chicago Latrobe. I now have several boxes of HF bits still unopened that I guess will be used for wood and plastic and if someone needs to borrow some.

Ken

 

[SpringHollow]

For those who do not know what a Cole Drill is:

Drilling Holes, Cole Drill, Ratchet Drill

 

[Big Barn]

For those who do not know what a Cole Drill is:

Drilling Holes, Cole Drill, Ratchet Drill

The drill's lost/scrapped/ long gone but I still have the Cole vice that came with it. Not a very good vice. I'm pretty certain my dad paid way too much for the set at the time. (Early 60's)



Terry

 

[ruffdog]

I used to own a cutting tool manufacturing company, so I'll give you my advice. Cutting oil or coolant is only necessary for deep holes - thicker than 1/8".

Actually, thin material and when the drill breaks through the back side is when much of the damage is done. Thin material offers no heat transfer away from the cutting and when it is breaking through, there is high heat and material can push away, adding to the friction. Machining parts for the paper manufacturing business meant 50% was stainless. It's just a different material with different machining characteristics.

 

[marchanna]

I agree, but this is based on the assumption the OP is only drilling a couple holes and then he's done with it. In a production environment you're always going to run coolant.