Costco/"Worksmith" 115 drill bit sets saga

Awl --
Some Qs came up some time ago regarding these drill sets, with most comments being pretty favorable (including my own), esp considering the price:
$20-39, TiN coated, etc. 135 deg point (above 1/8, iirc), but with 3/8 shanks, above 3/8.
My main criteria was longevity, and they seem to last OK, overall quality/case seemed decent. Never thought to check them via measuring the holes they drilled.
Goodgawd.....
I was form tapping 5/16-18 holes, which requires an L drill (.290), and after some peculiarities with the inserted set screws, I determined that the drilled holes were coming out at .304 -- !!!! Holy shit...... WITH spotting!! In a Fadal!!!!!
AND, the drill actually does measure 290!!!
How does a .290 drill that actually measures .290 drill a .304 hole?????? With no ostensible wobble, or other defects.
And yet, some bit sizes drill close to their size, so you cain't even *predict* the error. The problem *seems* to be particularly bad on the letter drills, judging from previous travails that I had not pegged to regularly errant bits.
Just an fyi.
I guess the moral to the story is, You don't always get what you pay for, but if you don't pay, the odds much much less..... like an effing accurate hole, ferchrissakes.
And, of course, I have a *bunch* of these drill sets..... I guess I'll use them to drill clearance holes for screws.
--

Mr. PV'd

Mae West (yer fav CongressShill) to the Gangster (yer fav Lobbyist):
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Proctologically Violated wrote:

PV:
    If the drill's lips aren't the same length (or angle), then drill may drill oversize. You could try resharpening them, that should fix the problem.
--
BottleBob
http://home.earthlink.net/~bottlbob
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My uncle could hand grind a drill bit that would drill an oversize hole, regrind it and drill an exact hole and regrind it and drill an undersize hole. He told me to figure it out...I haven't.
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Did he also walk up-hill to AND from school?
--

Mr. PV'd

Mae West (yer fav CongressShill) to the Gangster (yer fav Lobbyist):
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Proctologically Violated wrote:

With barb wire for snowshoes?
--


Regards,
Steve Saling
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On Wed, 1 Jul 2009 19:51:20 -0400, "Proctologically Violated"

Many years go knew an old guy who owned a drilling job shop. He could hand grind small drills and be dead nuts on. If I hadn't seen him regrind the drills myself I wouldn't believe it. For years his shop ran parts for Cherry Textron on tolerances they couldn't hold in house for the price he was charging them.
-- Tom http://tinyurl.com/5okkgz
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Impossible to drill an undersize hole. As the drill will not go through the hole. Sharpen the end offset as to the center point and you will get a bigger hole.
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Well, I've seen it done too. The trick is a rounded corner at the edge of the cutting edge going to the flute. Like a Racon sharpening http://www.winsloweng.com/articles/grindPerform_content.htm
Karl
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But that is like a step drill and the drill is made smaller part way up the shank.
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Take a fairly good drill and measure it at the tip and every 1/2" down.
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Buerste wrote:

Sure, but then we would have thread after thread as to which natural, biodegradable lube was better. Bear fat, because its long lasting, or Chicken fat, because its cheap and a lot easier to get. ;-)
--
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Human fat. It could be extracted from between the ears of democrats.
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Buerste wrote:

That stuff in rancid, and you have to strain out all the maggots. :(
--
You can't have a sense of humor, if you have no sense!

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snip---

No, it isn't. It's not all that uncommon.
Harold
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On Sun, 05 Jul 2009 08:19:06 GMT, "Harold and Susan Vordos"

Errr Harold, will you explain that a tiny bit.
I measure the shank of a, say .500", drill. Stick in the machine and drill a .450" diameter hole? In mild steel? 1 inch thick?
Cheers,
Bruce (bruceinbangkokatgmaildotcom)
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Errr Harold, will you explain that a tiny bit.
I measure the shank of a, say .500", drill. Stick in the machine and drill a .450" diameter hole? In mild steel? 1 inch thick?
Cheers,
Bruce (bruceinbangkokatgmaildotcom)
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Bruce,
There is a very good chance you measured incorrectly or the drill was undersize.
Bob (Harold knows his stuff) Swinney

Errr Harold, will you explain that a tiny bit.
I measure the shank of a, say .500", drill. Stick in the machine and drill a .450" diameter hole? In mild steel? 1 inch thick?
Cheers,
Bruce (bruceinbangkokatgmaildotcom)
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On Sun, 05 Jul 2009 20:42:03 +0700, Bruce In Bangkok

Harold is quite right. Ive been sorting out boxes of drill bits..and the shank diameter is NOT always the same as the bit diameter.
Ive measured Good .500 bits and they tend to actually mic out at .495-.502
Quite a range..and a head scratcher when the hole is too small.
Gunner
"Lenin called them "useful idiots," those people living in liberal democracies who by giving moral and material support to a totalitarian ideology in effect were braiding the rope that would hang them. Why people who enjoyed freedom and prosperity worked passionately to destroy both is a fascinating question, one still with us today. Now the useful idiots can be found in the chorus of appeasement, reflexive anti-Americanism, and sentimental idealism trying to inhibit the necessary responses to another freedom-hating ideology, radical Islam"
Bruce C. Thornton, a professor of Classics at American University of Cal State Fresno
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or about Sun, 05 Jul 2009 14:00:34 -0700 did write/type or cause to appear in rec.crafts.metalworking the following:

    I learned about the difference between "normal' drill bits and TiN coated ones. Didn't make much of a difference, just that the TiN drills made a hole some .005 over tolerance. Fark!
pyotr - pyotr filipivich We will drink no whiskey before its nine. It's eight fifty eight. Close enough!
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Damn, my posts aren't showing up on my monitor, but the responses to them are. Bear with me.
As has been alluded, drills can drill a hole that is undersized from the designated (and measured) diameter of the drill. It happens by the drill creating a less than round hole, so the minor diameter is smaller in size than the drill measures at the tip. A like sized pin won't fit the hole.
For those that don't know, drills are not straight. They are ground with a minor taper towards the shank, which is almost always a few thou smaller in diameter than the drill tip. That's to insure that the drill doesn't bind in deep holes, assuming they cut size. They have been known to!
Twist drills are a miserable cutting tool at best-----although they do create holes! The web of a drill does not cut-----it displaces metal so the cutting lips can remove it. That's why split point drills do so well. They actually cut at the web.
Harold
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