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Machinists: critique my twist drill sharpening.

6876 Views 65 Replies 23 Participants Last post by  fj40guy
Ok, I've read and heard about those expensive, fancy, store bought drill sharpeners. Drill Doctor is about the cheapest little thing you can buy. You can get crazy with a CNC twist drill sharpener that will run you $18,000 and cut a twist drill into a miniature mouse dildo.

BTW, we're in the metal shop, so these are not 'drill bits'. You gotta go next door to 'The New Yankee Workshop' to find those. Here in cutting oil land we call them twist drills. Don't ask me why, it's just what I read. :confused:

So, being a poor man, and hearing that 'old machinists' could sharpen twist drills on their own, in their sleep, I was of course intrigued.

Newer twist drills have a 'split point' edge. In order to sharpen them using this method, you have to 'thin the web' I don't have this problem since I have the cheapest bits around, so I don't have anything to critique there. I could figure it out I bet.

I put the grinder rest at an angle I figured was conservative.

I measured the cut angle by placing a large bit on the face of the stone and marking the shank resting on the guide with a sharpie. :rolleyes: Only the most precise methods for me!

I eyeballed the edge to get it centered, and I think I did pretty good. The picture I took was with one hand holding it 18" from my body. With two hands it doesn't walk at all. Using a center punch it doesn't walk either of course, and the hole's not egg shaped.

It's not the 'sharpest' thing around, but I drilled 7 or 8 holes, and had no dulling I could tell.

This is the drill I used as a guide:


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Here's a broken stub I had, as you can see, pretty short.


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This is how I eyeballed the angle. If the drills I'm sharpening are bigger, I bet the more accurate I will be according to the guide. With this small drill, it's basically touch and go. It takes a few swipes to get her centered ( the cutting edge that is.)


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Here's the tip. The fuzz on the end is some shavings.


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Here's another view of the tip and cutting edge. Sorry so blurry, it's 7:30 am on Jan 1st. I don't drink ya'll, but still, this is early for me! I stayed up till 3 last night!


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Here's all the holes I drilled before the video I'll show you. It stayed sharp. I wasn't getting perfect curls of metal, I was getting bits. But she bit right in and felt sharp to me. Certainly sharper than it was before I broke the fawker because it was so damned slow!


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Here's the shape of the hole. Yes, it walked on this one because I was holding the drill at arm's length, and let's face it, this old porter cable cordless has a pretty shaky chuck. I got it for cheap though.

When I use a center punch before hand, it doesn't walk, and in fact it doesn't even shimmy and shake like a dull bit will.


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Here's a .mov of how fast it cuts. Sorry, Quicktime! :emb: I like this format, so :flipoff2:

Secret: The real secret here is not how to center the point. That's easy.

The secret is how much to twist the bit in relation to the flute. That determines your cutting edge. So precision is key here, you want it as sharp on both edges, close as possible. Not only will a non-centered tip cause walking and egging, but two imprecise cutting edges will!

I didn't do too fawking bad considering the size of the work. I learned this in, with taking pictures, literally 10 minutes!

Here is a link explaining things, and some commentary by some knowledgable guys.

I could easily make my cutting edge more severe so she would bite right into hard metal. My demo work piece was soft so I made the pitch shallow. This all depends on how far you cut on the flute. You can change this at your liesure. Remember, this is more important than the 118 degree or 130 degree thing, I think. Unless that's what that means.

All I know is I just found a free method to sharpen my bits at anytime on a really coarse stone. I'm going to get a fine stone and try this on some tempered steel. In fact, an axle from an ATV that I've found to be junk (unless I can get the brake drum off, then I'm SOL cause I ain't drilling it!)

Anyway, happy trails, and tell me what big, boneheaded mistake I'm making or overlooking!

This cut the hole ~5/8" of an inch in 15 seconds using one hand at arms length on a 12v cordless drill with no cutting fluid. In soft metal. Not bad IMO, I can live with this as long as I can walk over to a grinder, even coarse, and whip out a sharp twist drill in 10 seconds flat!

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So, I figured out the sharpness is actuall the angle of the cutting face in relation to the flute. Knowing this, I can actually customize my twist drills according to application, and since it's so easy and FAST to do, I will be doing just that!

I just saved myself countless hundreds of dollars over my lifetime, over so easy a task!

So if you've got any tips, please tell me. This is one of the most kickass things I've ever done in the shop, and it just took me by surprise to try to learn how and find one link with instructions. So critique away please!

BTW, this made my twist drill magnetic. Is that normal?

Also BTW, these twist drills had some Ti (???) coating or something on them? Completely useless after you break the fawking thing off! And fawk it, I can't tell the diff. I read that the coatings only make a difference on a production basis, when it may mean that you can drill 10 more pieces with each twist drill, and when you're drilling millions of pieces, that's a worthwhile savings.

For us Joe Amateurs, that's a complete and utter waste of money! A scam that they even sell consumer twist drills with the coatings! All you need is HSS twist drills, and they're all at least HSS! So get the cheapest ones you can get I say, and sharpen them to your taste.
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Starslope said:
Whoa... amazing what holiday time off can to do some people :eek:
What's that mean exactly? :confused: :D
ForestCam said:
I like my angle flatter, sure they walk more but it's nice getting that one peice shaving.:D
I can't get away with that on this soft metal. If I did I'd twist this tiny drill in half. I experimented a little bit and had it engage the clutch of this cordless drill holder. So like I said, I went WAY conservative.

On mild stock or even hard steel, I would go aggressive.
ForestCam said:
I like my angle flatter, sure they walk more but it's nice getting that one peice shaving.:D
Actually, with two hands I can get one shaving. I just tried.
ForestCam said:
Two things I did learn from my dad, how to sharpen a chisel and sharpening drill bits.:D
Used my brother's Drill Dr. once and all I gotta say is I WANT ONE!:laughing:
If you can get one piece shavings, I have to ask, why? You don't have to do shit to sharpen on the grinder. I imagine with the DD there's SOME type of setup, no matter how simple. At least, you have to plug it in. My grinder is always sitting in the same spot.
64rovr said:
ahhh dude... a drill doctor is like $60... and takes 15 seconds to sharpen a bit...
$60 is a lot of money to me. I can buy dozens of drills with that.
That's cool, if I ever have a chance I will pick up a used DD 750.

Here's what I did on a hardened lawnmower blade. I'm very very happy with the results. Usually, this would take me all day.

I can go anywhere and do this as well. Sorta like stick welding, I'm glad I learned this before getting accustomed to a DD.


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frankenfab said:
The cutting edge (in blue in the picture) should be higher than the trailing edge (in red). I can't tell from your picture if you ground it this way. I bought a Drill Doctor Journeyman 400 and it is well worth the money. I use it all the time.
Yes that's the way it's cut. The adjustment of that angle is what makes the diff between a more aggresive and milder edge. Thank you for confirming that!
ForestCam said:
Well my wheel is shit at the moment (gotta get me a dresser) and even with the small amount of set up with the DD it's faster and easier. My brother went through about 100 old bits he had in a coffee can in about a half hour. Once you getthe hang of it it only takes a few seconds per bit and the biggest plus is on the big bits. Ever pull the it off to check your angle only to put it back against the wheel and fawk it up?:laughing:
No, I'm an expert already, what are you talking about? :flipoff2:

:laughing: Seriously, I'm having very very good results so far.
ForestCam said:

Cool beans!

Drill Doctor 750SPK $139.99 w/free shipping @Amazon plus there's a $10 mail in rebate!:D:D:D

Hmmmm...Sleggtools.com has the same model with the left hand chuck added for $10 more....desisions desisions.....:D
I was contemplating buying a DD, and adding it to my considerable tools list.... as in, this is $140 further away from my T/A 185TSW. Not anymore, this puts me a few weeks closer to my TIG welder! :bounce: :laughing:

As a matter of fact, I haven't seen a DD in use in person, but I've read the tech articles. At this point, I consider one a waste of money and shelf space. I'll qualify that because like I said I haven't used one. But at this point, I don't NEED one!
toryranger said:
flattening the drill point for harder material is a fairly standard thing to do. Watch that the two flutes of the drill are the same lenth when you resharpen it, if they aren't the drill will cut oversize. This can make a difference if you are trying to get a close tolerance hole or drilling for a tapped hole. I was a machinest for 30 yrs and preferred to hand sharpen almost all drills rather then use a machine. On a drill the face of the flute is what is actually cutting, not the end so the Tin coating is still on it. It isn't as good as a fully coated drill but still better then one that isn't coated. A good alternative to tin coat drills is to get cobalt drills.
Thank you! That totally confirms what I found, in my 'secret' paragraph. As long as you get them both the same, the hole will be perfectly round, and so tight the twist drill will actually 'pop' out when you pull it out.

I've heard like you say: Machinists would rather sharpen their own than use a machine, unless it was neccessary. That's where I want to be!

Now getting catalogs is a dangerous thing. I don't know jack about the machinery world, but I'm learning! I learned you can just get sick with this drill sharpening, and that the DD is an amazing little device to put split points on drills for $140!


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Supergper said:

the only reason you say you dont NEED a DD is cause you have never used one...once you use one you will agree with everyone else that has and say its a must:D

I love mine...get a perfect edge without heating the bit and I can choose what angle I want...and if I want to sharpen split points then I can do that...I wouldn;t go without a DD;)
Nope, don't need it. I just drilled a hole and tapped it out, just to see. No problem. If I'm having a problem with precision above that, I'll go buy a brand-new bit.

PBB, home of Bling-bling, get all the best, every tool for every possible application :rolleyes: :flipoff2:

It's funny that the old hands got by without all the crap that is supposedly 'necessary' if you listen to this forum.

*edit* Besides that, this thread is about bench grinder twist drill sharpening, not an ad for the Drill Doctor, thanks. BillaVista already wrote an excellent article about the Drill Doctor here. I can't imagine you have much to add besides testimonials, which don't belong in the tech forum but in Chit-chat. :flipoff2: So thanky anyway.
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