Never done it. Looks pretty 'gimmicky'.
I'm presuming you're talking about that thing that's essentially nothing more than a pencil sharpener and a pointy drill attachment, where you 'sharpen' the basal end of your scion, drill a complementary hole in the trunk of the tree and insert the sharpened end of the scion into it?
Guess it might work if you got good cambium apposition, but I don't see how one would bind the graft to stabilize it until it callused in.
Only useful application I can see would be possibly being able to create a new limb in a spot where you'd like to have one.

I agree with the previous post that it looks pretty gimmicky. Every year I stick new varieties onto my existing apples, pears, plums, peaches, etc. I've tried a great many techniques and they all work as long as you get the cambium lined up, so find a couple simple techniques that work for you and happily go grafting. Generally, I'll use a whip and tongue to attach scions onto size matched stock or sprouts and rind grafts for top-work onto larger branches or to start a branch where there previously was none. Both techniques are simple, fast to execute, and provide a very high hit rate. I stuck in 32 grafts last spring and had 100% success. All you need is a sharp knife and something to seal the union like parafilm...no gimmicks.

I got the drill grafing tip that I used on a drill. I had some extra cutting and I tested it with 3 different trees. I did it in the spring, right at bud break. I tried mulberry, plums, and apricots. I made sure that cambium is matching, and still none of them took. It may work on apples, or pears better. You may have a chance if drilled a 2 year old wood, and inserted a smaller scion. So that defeats the purpose.
I don't recommend it.

Bass

For those who are in love with geometry, engineering and math like I do, you would understand that the basic problem of using drill grafts is one of conic sections, particularly, intersecting cylinders.

1) In order for a near perfect cambial contact with two intersecting cylinders, the cut would be very complex and it could not be done by pencil sharpener.

2) If the hole that is drilled is not perpendicular to the surface, the sharpener cut on the scionwood should match the oblique angle, and no pencil sharpener that I know can cut such an oblique angle, and one should note that the intersecting surface would even be more complex to have all cut perimeters in cambial contact.

3) There would be unfilled crevices in the drilled hole unless you have a conical drill.

Now the only way to have a perfect fit for good cambial contact:
1) the stock should have a flat surface to contain the hole
2) the drill should be conical instead of cylindrical
3) the hole should be drilled perfectly perpendicular to the flat surface

If you can find all three conditions, then you have a chance. But satisfying such three conditions at the same time is highly improbable. So it will not practically work in most cases.

These geometrical facts directly support the observed failures by other members.

Joe
You're making my head hurt with all the talk of the geometrical complexity of it all. We homonids have been grafting for thousands of years...sharp knife...couple of sticks...life is good.
Mike

Mike, that's right! So I only use sharp knife or cutter. Joe

I think that we may need to take up a collection and award some prize money to Joe ... this may be the first time in history that the geometry of conic secions has been brought up in a gardening forum!

Kidding aside, it's interesting and definitely relevant to the discussion ... and the "drill-grafting" technique does sound as if it would be of very limited use.

Impressive information. I was thinking the drilling was a quick way to achieve the same goal. Thought maybe the drilled graft might take like a mammalian skin graft that fills in the missing pieces.

Could a bit of an 'imperfect' fit actually improve chances of a good union? Just trying to think of why some folks say it works for them. Like much in science, the devil may be in the details. Experimenting is such fun!
cella jane

Always wanted to try it, but never got around to it. Biggest drawback, seemingly, is the limited amount of cambium contact.

Will try to do it, if I have extra scionwood. But then I will have to readjust the cut with a knife for the nice contour contact on the cylindrical stem. Will not use sharpener only knife for shaping the scionwood stem. Will try to find a dremel bit that has conical drill shape.

I bought the veritas pencil sharpener type and it has failled me compared to my whip and tounge. It seems that you need the prefects size scion and hole. However it did get down to under 20 degrees after I grafted them. None of my cleft grafts looks ery promising either. None of the dozen or so drills I did seems to be taking. I used grafting wax and parrafin. Some even popped out. May only be good to make a new branch when you really need it and can try year after year. Cary