Drill Bits - Need some help and advice

[Big Barn]

Also get yourself a drill bit gauge to confirm sizes. Whenever I run into a dull drill bit I toss it in my 'to sharpen' bin and use my Drill Doctor couple times a year. Much more convenient to sharpen by hand but I'm only any good with the larger bits.



Terry

 

[Sodo]

Here you go.
https://www.youtube.com/watch?v=QbRPPxyw1hw&list=PL_MD_oorfJwFrXFSVwCvr-9t-M7q3tTOQ

I've sharpened by hand for 40 years and I'd have to say (by my hobby/maintenance POV) that video is pretty good but I've got a question.

I was surprised he didn't make much of a fuss about overheating the cutting edge. I always thought that once you turn color on a cutting edge you just ruined the heat-treat on the steel, at the worst location. Now you have to grind all the colored metal off plus more (also slower and still keeping it cool). Otherwise your bit won't keep it's sharp edge. When he's all done you can still see the discolored steel at the cutting edge and he proclaims it ready to go.

Have I been worrying about this for 40 years for nothing?

 

[Shield Arc]

It's been years since I watched that video. I agree, I won't let the drill bit get hot. Around here water is cheap, so I use lots of it.:laughing:

 

[truckdiagnostics]

Here is what I am talking about on the reamer.

Technically it is a bridge reamer, I start out with 3/8 hole and run it through to the 5/8. Works slick for drilling frame rails!
https://www.mscdirect.com/product/d...adTerm=0236040&typahddsp=02360402&hdrsrh=true here is the link it started out with MT2 tapper straight shank, they want to much. Then I remove the drill chuck from the drill press, and adapt to the MT3 tapper. bit the bullet go from 1/2 to 1" by 16ths.

 

[MinnesotaEric]

Here you go.
https://www.youtube.com/watch?v=QbRPPxyw1hw&list=PL_MD_oorfJwFrXFSVwCvr-9t-M7q3tTOQ

I've sharpened drill bits by hand since I learned how to do so in trade school years ago. I bought a Drill Doctor hoping to save time. The Drill Doctor lowered the drilling performance of my hand sharpened drills and so I threw the $120.00 Drill Doctor away to save others. I use 8" grinders with a fine stone. Learning how to sharpen your own drill bits also allows you to fix broken bits.

 

[NewfieDan]

For drill bits I prefer a cobalt drill. It. They last a long time and keep their cutting edge. The set I have is about 7-8 yrs old. Haven't needed to sharpen any yet. The set cost me close to $200 but to me they are worth it. Before you buy look into the cutting angle. Specific angles are more suited to certain materials. Fir example a 90* angle is a general purpose but. One with a 135* angle is best suited for cutting metal.

Don't waste money on titanium coatings. In my experience, after a couple of holes they are dull.

For my woodworking I use something called a brad point bit. They have a lip that shears the wood before the cutting edges remove the bulk of the material. Larger holes in wood I use a Forster bit or a hole saw.

 

[Sodo]

The Drill Doctor lowered the drilling performance of my hand sharpened drills……….Learning how to sharpen your own drill bits also allows you to fix broken bits.

I haven't even opened my drill doctor…

Every time I have an offending bit just sharpening it is quicker than reading the instructions for the doctor. Someday I should try it….

 

[LD1]

I dont like coated bits unless they are 1/2" an smaller. Which I normally dont re-sharpen. Larger bits are expensive, so they get sharpened, and that takes the coating off anyway.

Some good bits that arent junk, but not overly pricel either are hertel S&D bits. MSC carries them as well as some higher end ones, and some cheaper ones. I find the Hertel work well, good quality, and keep them sharp.

The issue with small presses is they just run too fast for the power IMO. Typical HSS bits in mild steel work well with a SFM of 80-100. Which calls for 300-375 or so for a 1" bit. But if you dont have the power to spin it that fast AND pull a decent chip, then they overheat.

For sharpening, I like a belt sander.

 

[torqotrac]

Hi gang, Just visiting over from lawnmower forum (sister to this). Some things that might be of value ...If you want to hand sharpen, two fundamentals: included angle and lip length matching. You can get a little gauge cheap that sets the angle and has graduations so you can keep comparing the two flute lip lengths as you grind. If the drill tip is not ground with equal lip length the drill will put out unequal chips (a clue) AND will not drill a round hole. What is difficult in hand grind is that you are looking at angle, lip length and cutting edge angle (clearance) all at once and being set by you free hand. Suggest you practice on drills 1/4" or larger as grinding smaller is difficult. You can save broken drills after you get good if the "web" is not too thick. WEB: the center of the drill which is narrow at tip of new drill and gets thicker up the shank. Sharpening a drill down the shank where it is thick makes starting the drill very difficult because you must force the thick web into the metal until the lip is reached so it can cut. Eyeballing "clearance" (cutting angle) of the cutting lip will come with practice as will the added clearance behind the cutting clearance necessary to avoid rubbing and not cutting. I use a lowly 60 grit grey harbor freight 8" wheel but it will burn quickly if not careful. Pedestal grinders typically have a little water cup for dipping, but go slow and feel the tip to avoid burn (annealing=softening ). Peck drill (downward pressure on drill and relax, repeat) and use lubricant on the metal (wd 40 for Al, oil for steel, nothing for cast iron). If helpful I will picture the drill gauge mentioned.

Edit There is a technique for web thinning by hand, but one thing at a time!

 

[LD1]

Also worth a mention:

IF using larger bits, like 1/2+, most are chisel tip and not split point. Meaning you need a pilot hole. But only the thickness of the chisel tip. Do NOT try to step up sizes 1/8" at a time like soooo many inexperienced people do. It makes the bit really grabby, and a very high probability of chipping the corners off the bit.

Drill a pilot hole, usually around 1/4", then right to size with the bit you need and cut out a nice clean chip.

 

[oldtimer 66]

SFM is surface feet per minute. That can be the tool and or the material. That is how much of the material and or tool that passes by a theoretical point in one minute in feet. Mild steel about 100 sfm. Inconel maybe 20 sfm. Aluminum say 300 sfm. Example 1.0 dia. drill in mild steel. RPM per the formula 400 rpm. Now the same drill in Inconel 80 rpm. Same drill in aluminum 1200 rpm. This formula is a rule of thumb for a starting point on cutting speed. This should all be on the Internet some where. Machinery's Handbook covers this extensively. Have at it. Later.

 

[LD1]

SFM is surface feet per minute. That can be the tool and or the material. That is how much of the material and or tool that passes by a theoretical point in one minute in feet. Mild steel about 100 sfm. Inconel maybe 20 sfm. Aluminum say 300 sfm. Example 1.0 dia. drill in mild steel. RPM per the formula 400 rpm. Now the same drill in Inconel 80 rpm. Same drill in aluminum 1200 rpm. This formula is a rule of thumb for a starting point on cutting speed. This should all be on the Internet some where. Machinery's Handbook covers this extensively. Have at it. Later.

And a 1" bit will have no trouble @ 400 in mild steel if the press is large enough and has the power. The heat is removed from the bit and part in the form of the chip. If you dont have the power to remove a sizable chip like most small presses, you toast the bit.

Most small benchtop type presses arent good much beyond 1/2" bits.

 

[oldtimer 66]

SFM is surface feet per minute. That can be the tool and or the material. That is how much of the material and or tool that passes by a theoretical point in one minute in feet. Mild steel about 100 sfm. Inconel maybe 20 sfm. Aluminum say 300 sfm. Example 1.0 dia. drill in mild steel. RPM per the formula 400 rpm. Now the same drill in Inconel 80 rpm. Same drill in aluminum 1200 rpm. This formula is a rule of thumb for a starting point on cutting speed. This should all be on the Internet some where. Machinery's Handbook covers this extensively. Have at it. Later.

 

[Shield Arc]

If the web of the drill gets to wide for my liking. I grind it to a point using the edge of the grinding wheel between the flutes.

 

[oldtimer 66]

Since we got into H.P. rule of thumb, one HP per c.i. metal removal per minute for steel. Roughly .5 HP per c.i. metal removal per minute for cast iron. Question: does it take more or less HP to machine aluminum and why? As compared to steel.

 

[KennyG]

I'm always surprised at people who don't like Drill Doctor. I'm not great at hand sharpening. I get variable results. The Drill Doctor is a breeze, takes only a minute or so and gets consistent results. I probably resharpen more often than I need to because it's so easy. I guess everyone is different.

 

[Big Barn]

I'm always surprised at people who don't like Drill Doctor. I'm not great at hand sharpening. I get variable results. The Drill Doctor is a breeze, takes only a minute or so and gets consistent results. I probably resharpen more often than I need to because it's so easy. I guess everyone is different.

Perhaps the entry level models aren't as good? Sometimes there's a reason for higher prices.

Terry

 

[Shield Arc]

I was given a Drill Doctor years ago. I thought it did an OK job. It just took to long to set up. I can sharpen a bit by hand before I could get the bit in the Drill Doctor clamp. So I gave it to my brother-n-law. He loves it.

 

[bigdeano]

I was surprised he didn't make much of a fuss about overheating the cutting edge. I always thought that once you turn color on a cutting edge you just ruined the heat-treat on the steel, at the worst location. Now you have to grind all the colored metal off plus more (also slower and still keeping it cool). Otherwise your bit won't keep it's sharp edge. When he's all done you can still see the discolored steel at the cutting edge and he proclaims it ready to go.

Have I been worrying about this for 40 years for nothing?

You're not likely to soften HSS by grinding. You can silver solder it to a boring bar (red hot) and it will still be hard when it cools. Carbon steel is a different story.

 

[LD1]

More HP for aluminum overall cause you are running faster and removing material quicker.

But I imagine the HP per ci is similar for alum as it is for cast iron.