On Monday, March 24, 2014 2:44:15 PM UTC-7, Cydrome Leader wrote:
jon_banquer wrote:

On Monday, March 24, 2014 10:35:59 AM UTC-7, Cydrome Leader wrote:

jon_banquer wrote:



On Sunday, March 23, 2014 4:05:10 PM UTC-7, Cydrome Leader wrote:



wrote:







As a newby I don't know where to buy drill bit sets.







I want high precision, no bits that give me a .190 hole from a .186 drill bit; and not a 123 hole from a .125 bit either.















On EBAY I foudn 12 piece sets for $8.95 (from China probably), but when I search other sources the same type of sets are around $350.







Any suggestions?







alofsax















You never said what sizes or how many bits you want it a set, but Republic







Drill sells alleged to be made in USA drill index that come in a Huot box.







I have the number and fractional sets in screw machine length in black







HSS.















They're great, mostly because the're super short. I got mine from Little







Machine Shop in CA or Victor Machinery in NYC. Both places are respectable







and will not pull a "whoops it's chinese, we forgot to update the photo







and description" scam.







Should you ever have to drill tough alloys you will be far better off with cobalt. They hold up much better.







Any opinions of those hard material drill bits that lack a twist? What



about center drills vs. 90 degree spot drills?



I call hard material drills that lack a twist Hi-Rock drills. They are made of carbide. They burn through the metal, give you a nice finish and don't leave a burr. I don't use water based coolant when I use them. I turn the coolant off and use Molly-D. If you break one off in the part you're usually completely ****ed.



the cross section looks similar to a tap. can a tap extractor be used to

remove them?



Somehow, I've never broken a tap off below the surface, but I only tap by

hand and am not in a big hurry.

Tap extractors almost never work, period. I don't even bother with them. When I bust a tap, I use a carbide end mill to break it up. You develop a really good feel after doing this enough times. I usually can get broken taps out pretty quickly.

When a carbide High-Rock drill busts usually bits of carbide embed themselves in the hole and it's game over.