Buying new drill bits

I have found that one universal rule applies to all drill motors. Do not run it wide open. A drill cuts faster and more symetrical if you turn it quite slow. If you hear a drill motor screaming wide open, some body needs training. I don't think I turn any of my bits faster than about 500 RPM, and they pull into the material nicely all by themselves. It is truly amazing how many mechanics and machinist have not been taught that. And cutting fluid is used to cool and slush the chips from the work site so the bit can continue to cut.
Bob
 
Guilty as charged. I over simplified and made it wrong. You got the gist of what I was saying though. Machineries handbook even has a formula. Sorry for confusing the discussion. thanks for keeping it from straying too far.
Bob
 
biguglycaprice said:
I'm looking to get a new set of drills for using in my press and the lathe. I use cobalt thunderbits at work and while they are great, I cannot justify spending that kind of money for use at home. I don't know a whole lot about the different types: bright finish, black oxide, bronze oxide, etc... Or why you would buy one type over the other???

I mostly work with steel.

So, what should I be looking for in a new set?

Are any of the imports worth looking at or should I stick with American?


Thanks
Click to expand...

I bought the Harbor Freight 115 piece cobalt set (5% I think). I must say I'm very impressed so far. They drill accurately sized holes, with proper looking chips. They stay sharp too. Not quite as long as the 8% cobalts, but definitely not a problem... Bang for the buck for sure...

The TiN set I bought from them a few years back was not nearly as impressive. They dulled easily and often drilled oversize.

John
 
I'm in the market for a number/letter/fraction set, What should I expect to pay for a middle of the line set? I had a nice set 30 years ago when I worked in the aircraft biz (company supplied) but sold them to a friend who still has them. Think I may buy the HF set for now then upgrade and have a cheap set for wood and non precision drilling and a good set that's off limits to my friends (except Benny).

Other than length what is the difference in jobber bits versus regular bits?
 
Some math for drilling holes.

Drill speed = cutting speed (material being drilled) X 4 divided by the diameter of the bit.


Stainless 50
carbon steel 100
yellow brass 200
aluminum 300


just to name a few

Don't worry about being "perfect" on the speed, as close as your machine will get is good enough.
 
You must log in or register to reply here.
Back
Top