Costco/"Worksmith" 115 drill bit sets saga

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.

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.

Did he also walk up-hill to AND from school?

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.

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

With barb wire for snowshoes?

A drill doesn't center itself with its point. It centers itself wherever the forces from the cutting edges come into balance. If the lip heights, or the lengths and angles of the cutting edges, aren't identical, then the drill cuts off center, and effectively bores the hole oversize. If you have a good grinder and like playing trigonometry, you can do this on purpose with some remarkably reliable results.

Making a drill cut undersize is more difficult. You have to fix it so the different lengths or angles produce cutting edges that aren't the same distance ahead of center.

Despite what JB might think, a Darex grinder is a really good way to make drills that DON'T cut to size, precisely because it can't repeat the lip heights. And regrinding your drills means you lose all that nice gold coating you paid for. If you have any kind of cutter grinder, you can touch them up yourself, albeit slowly and in low volume, and get better results than the average Chinese manufacturer. Otherwise, since the drills themselves are probably too cheap to justify the cost of quality resharpening service, just use them for rough stuff and buy better drills when you need to form tap a hole.

KG

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

age

Ever try drilling, opening up, a hole in titanium, say a 1/32"? good luck. Whats the longest hole you have drilled? non critical, like mold water lines? gun drill machines don't count. Drill doctor? Darex? what about a Sterling drill sharper? Now thats a drill sharpner. For my home drill set, I ground hex's on the shanks on all drills above 3/8" sweet no chuckey needed.

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Come on, Tom. He was using rubber drill bits. ;-)

Oh, it IS wobbling, for sure. It is a well-known fact that drill bits drill oversize. How much oversize can be VERY variable! Feedrate can make a big difference. You will often see the entry start out triangular, or sometimes pentagonal, and then smooth out somewhat once the drill is half a diameter or so deep. If you need a hole to be on size, you drill undersize and ream. .014" oversize seems like a greater amount of oversize than I'm used to, but I see it all the time, and compensate if needed.

Jon

But that is like a step drill and the drill is made smaller part way up the shank.

Take a fairly good drill and measure it at the tip and every 1/2" down.

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. ;-)

Human fat. It could be extracted from between the ears of democrats.

That stuff in rancid, and you have to strain out all the maggots. :(

No, it isn't. It's not all that uncommon.

Harold

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)

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)