Drill bit web thinning.

[tonyfoale]

Prompted by Bob's excellent video on split point drill bit sharpening at http://www.homemadetools.net/forum/s...arpening-70940 I present my own simple tool modification for the same purpose.
Bob talked about drill point geometry and split point sharpening so I won't repeat that although I use the 4 or 6 facet geometry explained in my earlier post at http://www.homemadetools.net/forum/h...6205#post83247 .

Web thinning at the point of the drill enables a more accurate start to a hole and reduces wander, it also removes or reduces the need to drill a pilot hole with a smaller bit because the point of the drill is in effect the same as a smaller drill.

I had a little grinder designed for sharpening chainsaws which I used sometimes for web thinning but the blade was at an angle and was movable, this made it less than ideal for drill bit work. This is pictured below.

Click thumbnails for full size images.

To improve its utility I made this simple holding support from some bits out of the scrap bin.



The next pix show the grinder mounted on the support. It is now very convenient to use.



The wheel that came with the grinder is 3 mm wide which is fine for larger bits but too thick for smaller ones. Fortunately the hole diameter in 1 mm angle grinder cutoff blades is the same and so I change over to those for smaller bits.


Showing a 3 mm blade mounted with a 1 mm cutoff blade below.