Tooling up - Drills

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Mirage33

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Ok, first post, here I go with the dumb questions!
I've been in "tooling acquisition" mode lately to set my "workshop" up, centered on a 7x16 mini lathe . As a beginner, I bought a set of 115 jobber drills at a reasonable price with LMS. Reading on the forum, I'm realizing that I perhaps made a mistake as the drills have a black oxide finish while I will mainly machine aluminum, polymers and brass. I will of course process some steel from time to time but it won't be my primary material. I understand that black oxide finish could cause the drills to grab aluminum rather than cut it and it seems that the preferred bit finish should be "polished". I already went above and beyond my initial budget and am reluctant to spend again to get a "polished" set.
So, metal gurus, could my current bits (black) work with a lot of coolant/lubricant? I am not going to use these intensively but wonder if they could ruin a work.
Thanks for any answer.
 
Ok, first post, here I go with the dumb questions!
Click to expand...

First, there are no dumb questions here. I don't have a mini lathe so I'm not the best sounding board. I have heard others that do own/operate them that at times jobber bits are too long, that mechanic's bits (shorter) fit the bill better.

In regard to the black oxide finish, :shrugs:.

I got in on the 'group buy' on bits recently and they're not BO (they're shiny) but they work really well. I've never had fractional, number & letter drill bits before and now I don't know how I lived without 'em!
 
The black oxide will hold lube better than uncoated. I think you are okay. The length may come into play but I just get those short ones as I need them. So far I use the 115 piece set like crazy and have a few machine screw length for those occasions.
Dave
 
I've not had a problem using black oxide in aluminum. Peck drill (in about a drill diameter or so, then pull out to clear), and my favorite cutting oil for aluminum is WD-40.
 
For me its more the quality of drill bits that has caused drilling issues the coating dosn't seem to be a biggie in my exerience. Also with black dril bits you can easily see when a large chunk of ally is stuck on a ti,p somthing that can be harder to spot with silver or gold finnish drills.

Stuart
 
Well, thanks for the answer guys. I can breathe !
The lathe is 7x16 and provides good clearance for the jobbers
 
I've worked in an all brass, copper, bronze shop. The old timers would "dull" their drills, make the cutting edge not so sharp. In fear of it grabbing and pulling the drill into the work piece. Years later I worked in a shop that turned aluminum. Now keep in mind I ran a haas sl 30. I did alot of drilling and never has any issues using conventional drills. Of course all my turning inserts has a high shear to them. The softer the material the higher the shear. Aluminum, plastics, ect.
 
I wouldn't think that grabbing and pulling the drill into the work piece would be a problem with a clamped workpiece and power feed on a big, rigid machine.
 
I've drilled hundreds of thousands of holes in 2024, 6061, 7075 and Ti with hand drill motors and Quackenbush units. Almost always with standard black coated HSS drills. Most guys working at home are not going to need to deal with carbide, cobalt or diamond drills...if you do, then that's a whole 'nuther world.... Lube, speeds and feed rates are what matters most. I used to tell the guys that were training under me, that if the drill wasn't making worms with the swarf, then drill speed and feed rate were wrong for the material. I've had HSS bits, when turned at proper speed and feed pressure, last more than 100 holes thru Ti plate, when other guys doing the same job couldn't finish a plate with 40 bits of each size.

As to grabbing...a bit will grab if you break thru the back side of the material with too much force, or if you step up too much size at one time. A lot of the holes I drilled were thru fracture critical bulkheads and fittings. Most of the holes were piloted via a #40, then brought up by using a #30, then #20, an #12 then reamed with a .199", all with a hand motor and a drill block. Hole requirements were .199-.201" finished, with ecentricity, perpendicularity and angularity call outs based on location. We had guys that would never seem to learn that going from a #40 to a #12 direct would almost always give them an out of tolerance hole. I spent hours fixing those types of screwups.

As to buying bits...unless you need the length, go with jobber length and buy in packages of the individual sizes you need. I tend to keep #'s 50, 40, 30, 20, 12, 11 and 10's on hand and in lengths from jobber to 12" for most of what I do. Other sizes, I'll order as needed.
 
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