Drill Doctor

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sansouci
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Drill Doctor

Post by sansouci »

I've seen this product on TV for a while and was thinking it might be helpful. However, many of my bits are nitride coated and the sharpening process removes the coating so there is a trade off.

Let's hear it if you've used it.

--Ken
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Masked Man
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Post by Masked Man »

Hey Ken,

I don't have one but I was curious enough to look for reviews online and found this one. Seems like a sensible investment especially if you can find one used on CL.

Keep the shiny side up

Phillip

http://www.machinistblog.com/review-drill-doctor-750/
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sansouci
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Post by sansouci »

Phillip,
Thanks for the link! Are you the birthday boy? Congrats and enjoy Big T#ts Fr#day!
--Ken
Sansouci
84 E24 633Csi Auto, Bronzit/PearlBeige 6997510
93 E32 740il M60 Auto, Alpenweis/Ultramarine
60 528i M30 5-speed Green/Beige (crushed)
71 240Z 4-speed White/Blue (rusty & sold)
65 396 Chevelle 4-speed, Marina Blue/Black (stolen)
Chris Wright

Re: Drill Doctor

Post by Chris Wright »

sansouci wrote:I've seen this product on TV for a while and was thinking it might be helpful. However, many of my bits are nitride coated and the sharpening process removes the coating so there is a trade off.

Let's hear it if you've used it.

--Ken
The brother-in-law had one and he let me borrow it. I sharpened everything in sight. I have a numbered set (1-60), a lettered set and several fractional sets. I don't remember how small a bit I tried to sharpen but it did a fine job on a wide range of sizes and IIRC, it was fairly easy to use and put a nice edge and cutting point on the bits.
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Da_Hose
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Post by Da_Hose »

As I understand it, the nitride coating allows the bits to stay sharp longer. If they have dulled out, then the you have worn through the coating ... so sharpen away.

Jose
1987 M6 - My dream car
Chris Wright

Post by Chris Wright »

Interesting thread on sharping nitride-coated-drills:

http://www.practicalmachinist.com/vb/ge ... lls-87300/
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hornhospital
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Post by hornhospital »

The last post in that linked thread brought up the purpose (well, sort of) of having titanium coating. It keeps the metal being cut/drilled from sticking to the flutes. On carbide cutting tools it does the same thing, helping the flow of chips off the cutting surface.

About the Drill Doctor: they work pretty well within certain limits. I was a machinist for 28 years, and learned to sharpen drills by hand (no guide), which is much harder to learn than using a drill sharpening jig like the Drill Doctor. About 15 years into my career the shop bought a Darex drill sharpener, kind of a high dollar Drill Doctor. It worked great, but was limited as to the maximum size it would handle. I still sharpened drills larger than 5/8" by hand. We had some pretty good size drills....one was 1-31/32". Most of the large holes we drilled with carbide inserted tools, but in the engine lathes we still used twist drills. Eventually I got a Drill Doctor for use in my shop at home. It's one of the early, smaller ones. Works great on drills from about 1/8" on up to 1/2", Drills smaller than 1/8" get real iffy. IF they center perfectly in the chuck, and IF the grinding wheel is in good condition it MIGHT sharpen the drill accurately....or it might not. For the smaller drills you are better off buying good quality new ones if the hole size is critical, such as drilling for a tapped hole.

That's my $.02 worth.
Ken Kanne
'84 633CSi "Sylvia"; '85 635CSi "Katja";'85 325e "Hazel Ann"; '95 M3 "Ashlyn"
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Brucey
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Post by Brucey »

FWIW I was taught to sharpen drills by hand, and, on a good day, I can do it, too. Not as well as a time-served machinist, but well enough for my purposes.

When sharpening, the TiN coating is obviously lost on the end of the drill but that will still leaves it in the flutes and on the OD (if you are lucky) where it can do some good.

Theory would be that I am using my drill press, and I have a box full of drills (with spares in all the common sizes) that I have thoughtfully sharpened ahead of time, and I can just go in there and I'll be tooled up and ready for action. But the reality is often that I'm in the middle of a job using a hand-held drill and I suddenly have a drill that needs a new edge put on it, because I don't have a box full of sharp spare drills.

You would be forgiven if you thought this might provoke a little ghetto-improvisation; this is often exactly what happens. In fairness I'm taking my cue from some factory produced drills that I have used in recent years, but I now break several of the 'golden rules' I was taught re. drill sharpening.

I was taught never to touch the flute itself, and to create a particular shape to the drill tip, like this;
Image

Which (barring special drills) is how most drills come from the factory.

I now tend to do something a lot different to that, especially if I'm using a hand-held drill. It has never been the only way to sharpen a drill; but my idea of a good shape is one that is easier to use and is also quick and easy to replicate using the tools you are likely to have to hand. So 4mm and up, I use a super-thin angle grinder cutting disc to tickle the edge of the flute, grind a heavier relief on and so forth. Effectively you can create a simplified version of a so-called 'split point' drill geometry.

Image

My ghetto version of this simply extends the main cutting edge towards the centre of the drill to create a split point that is probably less strong than the conventional one but it is strong enough for most jobs. (IIRC You can buy drills a bit like this, I can't remember where from exactly.)

[edit; the closest I've seen is the 'facet point grind' on slide 10 here http://www.guhring.com/ELearning/VideoPlayer/?id=002 ]

If you do this right, you can have a drill that requires much less axial force to cut, finds centre better (smaller chisel tip), drills cleaner/easier without a pilot drill, and even produces less heat during the cut.

[NB. Because you can modify the flute angle, the cutting edge can have about 85 degree included angle if you want; this means it is potentially much stronger and more chip-resistant than a conventional drill's cutting edge, which between the flute angle and the relief angle will be nearer 65-70 degrees.]

Best of all, it is much easier to resharpen the drill, because the working edges can be resharpened in just two (or four if you tickle the flute/point edges too) simple flat cuts.

When you resharpen, you need only remove a little material to produce a fresh edge. There is no danger of overheating the bit, and you never have to leave any kind of micro-burr on the cutting edges. If I'm working under a car, I don't even need to get out from under in order to put a fresh edge on a drill if I have my angle grinder to hand!

You can modify the way the drill cuts with tiny changes in the relief angle, and these can be adjusted quickly and easily to suit the job in hand.

So I have not bought many new drills for a long time now, except in smaller sizes where it is very fiddly/difficult to create a decent drill shape. I go down the shops for those and I can buy them ten at a time for a couple of quid so it just isn't worth messing about with those anyway.

I'm sure that some folk will consider what I suggest as some kind of machining heresy but I have found it works for me!

cheers
~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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