The bit has exactly the same taper as a standard pencil sharpener. To graft, you sharpen a 6" length of scion (branch to be grafted) in a pencil sharpener and then use the Plugger® in your drill to taper a hole to a depth so that the cambium of the scion mates with the cambium of the tree. Insert the tapered scion in the tapered hole and seal the join with grafting wax or tree wound dressing. In a couple of months, the new branch will be strongly growing in this new position.
Full instructions are included. It is an easy way to introduce yourself to grafting, and create the exact plant shapes you want. Bit has a 10mm (3/8") shank. An extra-sturdy pencil sharpener is also offered separately.
The Pencil Sharpener is no longer available.