How To: Sharpen twist drills

[Mike K]

We all use twist drills and sharpening them can be a pain . That is, until a smart person came up with the 4 facet grind method . I do it free hand , I just mark a 59 degree line on the grinder rest but some use complicated jigs and guides . Basically, you grind four flats onto the drill. After sharpening a few times you also need to thin the web , thinning the web narrows the chisel which is the section on the centre tip that doesn't do any cutting at all . Going ahead, you can do the split point grind which provides a sharp tip at the chisel , doing this this greatly reduces the force required to drill through anything

https://www.youtube.com/watch?v=LjQdNQ-buHo

https://www.youtube.com/watch?v=I5b6h1Vddes

[Mike Cecil]

Interesting, Mike, thanks for posting.

I purchased a Drill Doctor DD750X which works very well if you are careful, and is adjustable with regard to point and chisel.

Mike

[Bruce Parker (RIP)]

What you don't do is let your kids buy you those yellow titanium coated drill bits, the ones in the pretty packages that are irresistible to them as Father's Day gifts. I figure they are mild steel coated in yellow and only good for one cut through pithy pine. Try them on a sheet of, say, 18 gauge steel and they howl with other worldly shrieks of protest until the friction makes them glow red and they melt. They will leave a scratch on your 18 gauge but surely no hole.

Now those double pointed short 1/8" pilot drill bits....I LOVE DEM BABIES!!!

[Lynn Eades]

Agree 100% Bruce!

[Jacques Reed]

Very interesting Mike,

Nice simple jig for a change compared to many on the web.

I like those pilot drills too, Bruce, and I have a couple of stub drills in larger sizes which I use in thin gauge steel. Being short, unlike jobbers drills, they don't get the wobbles and create that wonder of engineering science, "The triangular hole".

Don't walk into your local hardware store and ask for them though unless you want a blank stare back from the kid serving you. They are readily available however at good industrial supply businesses. Shown are an 11/32" and a 7/16" stub drill. Both are made by Sutton, an Australian and N.Z. company. Not Chinese gold coloured either.

Cheers,

[James P]

Originally Posted by Lynn Eades

Agree 100% Bruce!

X2 in agreement.

[Mike K]

Ah yes, the yellow coated Aldi drill sets sold in the round dispenser, good for about two minutes of use in mild steel Been there and I won't be buying them again.

A friend of mine has a Drill Doctor, not the 750 model but the smaller version that does up to 1/2" drills. We had a session playing with it. The Doctor is a somewhat fiddly and fussy instrument , it needs to be fine tuned for best results.

You can also buy centre drills. These are normally used on a lathe , the first step before using the normal twist drill when making a bore in a work piece . The centre drill makes a accurate dimple in the work piece for the normal twist drill to locate itself . Without the dimple, the twist drill will wander and walk over the work face.

There is a chap in the U.S, who has a career lecturing the engineering departments in universities on the science of sharpening twist drills !

https://www.youtube.com/watch?v=Ot8wPGQW3JI A good explanation of how centre drills work. Stefan is a typical German with his precision methods of machining .

[Michael R.]

Originally Posted by Mike Kelly

Ah yes, . .

https://www.youtube.com/watch?v=Ot8wPGQW3JI A good explanation of how centre drills work. Stefan is (edit) with his precision methods of machining .

. . . has anyone watched this video by adjusting the playback speed 2x ?
Tap the video once for the menu overlay, tap the three dots in upper right, tap playback speed, select a choice, i.e. 2x

[Jonathan Moore]

Or, when you start out in your engineering life you ask your boss to do it for you and eventually he gets so peed off, he hands you a new long series 5/8" drill bit which he has ground flat and after showing you how to grind it correctly he grinds it flat again, then its your turn. After each attempt he grinds it flat and this goes on until he is satisfied, then the drill bit gets smaller and so it goes on. After many hours you eventually get the hang of it, or so you thought because then you have to start drilling test holes to ensure that the drill cuts to size. Believe me, you never forget and it teaches you all you need to know about angles and clearances which applies to grinding other cutting tools as well.

Jon

[Mike K]

Another drill sharpener . The Vevor appears to be a nice machine but it looks like it is limited to max. 1/2" size drills. Most of us would be using larger drill sizes than 1/2"

https://www.youtube.com/watch?v=4TGon_xq80M