I am able to regrind drill points reasonably well by hand on an offhand grinder but having read quite a bit about the four facet method of sharpening I thought I’d give it a go today. (Don’t hold your breath mind!)

This is my little T&C grinder I used to do the job:

Standard angles used for the drill point – 118 degrees included with the recommended 10 degrees for the primary lip edge and 25 degrees for the clearance angle – these angles being recommended by Harold Hall in his book on tool and cutter grinding.

My first attempt on a 3/8” drill left primary lips distinctly out of parallel as seen in the pic.

I experimented a little and found that by inserting a .1” slip between the tip of the indexing finger blade and the indexing ring register I was able to bring the primary lip width back to, approximately, parallel. (I have yet to work out what is going on there!)

So does it work? In short, no – at least on this first attempt. I tested the finished result by chucking the “sharpened” drill in the tailstock and drilling a bit of 1” dia aluminium. The drill wandered on the bar end so I used a centre drill to give it a start then had another go. It drilled reluctantly with the swarf coming away mainly from just one edge which leads me to believe that ER collets are not suitable for this purpose. Oh well, it was worth trying!

So a disappointing first attempt but nil desperandum as they say, I’ll have another go in a day or two.

Rik

Update to my OP. The disappointing results I have recorded here, were, it transpires, caused by the drill itself – it was bent! I only noticed this morning as I attempted to have another go with a different drill.

So, I have ground the point on a fresh victim and this time the visual result was more encouraging:

So does it drill ok THIS time? Sadly no. It was pretty hard going on good quality aluminium rod producing uneven straggly swarf again, mostly from one edge only.

As I found the procedure over fiddly even using an accurate T&C grinder I have decided for the time being to abandon “four faceting” and revert to sharpening on the offhand grinder. Life’s to short to “fiddle” it away.

However, if you are contemplating trying this method of sharpening please do not let my experience put you of as I might well be doing something wrong. After all, Howard seems to be quite pleased with his results.

On the positive side, grinding the second drill gave me a chance to try out my new CBN cup wheel. It knocks spots of the aluminium oxide wheels I have used in the past – very pleased indeed.

Rik

Whatever gets the dirty job done Neil – results is what matters isn't it, wasn't it?

Rik