Sharpen drill bit on a drill press

If you're talking about the Drill Doctor the chuck has a cam--as you rotate it it moves the bit in and out to as to have the flute properly ground.

Reply to
J. Clarke
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I've got to second that. I was tired of springing for new bits, especially the expensive 18 inch long 1/2 and 3/4 bits. I got a drill doctor, and it's saved a ton of money. I got the top end model (for the 3/4 inch bits), and it also does split points -- great for metal drilling. I was skeptical as well, but this is one of those rare tools that does exactly what it is supposed to, does it easily and well, and SAVES you money.

tt

Reply to
Test Tickle

[snip long and useful lesson]

Thanks, Bill -- that's a keeper.

Reply to
Doug Miller

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Whoa! Talk about 'Deja Vu', just had a major flash-back to my machinist apprenticeship at the ship yard many years ago after reading this.

Same, same, 'sort the bolts', 'sharpen the drill bits', followed by "This here's a properly sharpened 1/2" HSS straight cut tool bit for that engine lathe over there. Here's a bucket of dull ones, make 'em sharp."

Don't do much machine work these days, but I don't buy a lot of replacement drill bits either! ;^))

Len

Reply to
Len

A cam.

Reply to
CW

The Drill Doctor and the angle guide are almost certainly doing much more than you think. Twist drills are deceptively complex.

Nope. Take a look at the tip of a fresh drill bit- in particular, the fact that the tip is not pointy like a pencil.

You can sharpen them freehand on a belt sander or fine grinding wheel, but it takes a little practice, and it really helps to have someone show you how in person. I'll try to descibe it, but I don't know how much it will help.

Basically, there are two huge things to worry about- The first is the tip profile. It should look like a forward slash ( / ), and not a point. The middle of the slash should cross the center of the bit.

The second is the "wing" angle. It should be 135* on most bits.

To get the profile right, you need to start grinding near the cutting edge (be careful not to round it off), and rotate the bit until it has ground that entire side. You can do this several times, but you're not rotating the bit all the way around. Once you're happy with the first side, lift the bit off the wheel, and rotate it 180* degrees, and repeat the process until the tip profile is centered.

It takes a fair amount of practice, but it's not too tough once you get the hang of it.

The drill sharpeners have an indexer to get the bit in the right position, then lock it so that it is properly aligned with the cams. As you twist the holder, it rides on cams to raise the bit appropriately as it nears the back of the grind. Well worth the $$$ to get one if you've got a lot of bits to sharpen, IMO.

Reply to
Prometheus

If you know how to sharpen by hand, I'm sure you're also aware of how long a drill bit can last, if you sharpen them when they get dull. Throwing them out because they got dull is like tossing a chisel because it got a nick in it, or relegating a scraper to the job of glue-spreader as soon as the burr wears off- people do it all the time, but it's sort of an insane practice. If you actually use up one set of drill bits, you've more than paid for the cost of a drill doctor in replacement bits you didn't have to buy.

Reply to
Prometheus

Ditto.

I didn't get to the lathe bit part until I took an intro (Machine Trades

101) class at the local Community College. On the other hand, my nearest "hardware store" is a Production Tool ;-)

I've taught that drill sharpening technique to a lot of guys since - but always in person. I hope that the written instruction was sufficient for the OP (and others) to follow. It's just ridiculous to throw away a 3" long drill bit just because the first .005" of it is dull.

I would like to add three safety tips that apply anytime a grinder is to be used:

1) NEVER stand in line with a grinding wheel when turning it on. If it's ever going to shatter, this is the most likely time for it. 2) NEVER mount a wheel that doesn't ring like a bell when suspended from a nail and given a tap on the side with a small piece of metal. It should be presumed to be cracked and just waiting for you to turn the grinder on with it mounted. FINISH BREAKING IT to keep anyone else from trying to mount it. 3) Eye doctors can use tiny, but powerful, magnets to tease small chunks of metal out of your eye ... but grinding wheels aren't metal, are they? Wear GOOD eye protection when using a bench grinder or sanding belt. Wear goggles. Better yet, wear goggles under a face shield. Do NOT rely on temporary side shields. DO NOT rely on your prescription lenses. Blind is forever.

There are other safety rules for grinders (provide for lung protection, no grinding on the side of the wheel, keep the grinding platform within the thickness of a dime to the wheel, and so on) but these will do for a start.

Bill

Reply to
Bill in Detroit

The method you propose will not duplicate the geometry of a correctly sharpened drill bit. I'm not sure I can explain it verbally, but here goes: the surface that trails the cutting edge must be angled so that iit provides a clearance angle for the cutting edge. If the bit was sharpened by merely spinning it against a fixed abrasive surface, there would be 0 deg clearance angle. Using such a bit would be equivalent to trying to lift a shaving with a chisel while keeping the flat back flat against the wood. IOW, without the clearance angle, the cutting edge cannot actually contact the work.

The good news is, in larger drill sizes, it is not too difficult to sharpen a drill bit to effectively cut wood using an ordinary bench grinder. With more practice, you can do a passable job at sharpening a bit to effectively cut metal as well. There are some good books out there that will explain how, or perhaps you know someone who already knows how. I was lucky enough to have an old machinist show me how over

30 years ago. That guy would actually take a drill bit to the grinder and custom grind it for the type of surface he was using it on. BTW, if you are only drilling wood with a twist bit, you can steepen the effective cutting angle quite a bit (no pun intended) than the general purpose metal twist bits and they will work a lot faster & cooler.

Smaller sizes are tougher to regrind by hand, depending on skill, eyesight, steadyness of hand, etc. For me, anything smaller than 1/4" or maybe 3/16 is a throwaway.

Reply to
lwasserm

skill,

than 1/4"

Those various sized/shaped ceramic sticks available from Garrett-Wade, etc., work quite well for hand sharpening smaller sized drill bits.

Hold the bit upright in a vice and run a 600/800 grit flat ceramic stick from the back of the flute towards the cutting lip.

Use the same pressure and number of strokes on both sides.

Repeat with finer grit ceramic sticks until you've got a good edge.

Use a 1200 grit oval shaped ceramic stick to knock the burr off the cutting lips. The oval shape allows it to fit into the flute of small drill bits with less chance of creating a groove than the edge of a half-round ceramic stick (learned the hard way).

I've been able use the ceramic sticks on drill bits down to about #60.

Len

Reply to
Len

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