Drill sharpening

[chimpboy]

group buy time ?

Id be up for one if we can get a good price.

x3

the DD750x at $500 retail is still going to be out of my price range as a group buy I expect. but an interested if the price is right.

- David

They are going for only $420 on ebay (in Australia, waaay less in the US but wrong voltage)... so surely a group buy would have to be sub-$400.

http://cgi.ebay.com.au/Drill-doctor-750 ... 35a5eb33c6

[me3@neuralfibre.com]

For the sharpening guru's on the thread

http://www.mmsonline.com/articles/choos ... t-geometry

Fig 4 and Fig 5

Seem to be the most interesting. The DD won't do these I don't think.

Assuming I use a DD to make up for my sharpening inadequacies - what are your thoughts on doing the secondary releif angle at the edges.

"During drilling operations, the by-products of rotational energy are chips and heat. Multi-faceted geometry generates less heat than any other drill point pattern. With equal diameters, the multi-faceted drill features 50-percent less thrust and 60-percent less heat than a conventional drill."

Anyone played with hand grinding these?

If you read the article - the modified split point sound cool.

Also - some of you have referred to wheel types.
Are some wheels on a grinder better than others?
Do you use the sides or the face of the wheel?
Is a square edge on the wheel important?
What about using a linisher?

Thanx
Paul

[nastytroll]

never use a linisher, I'm sure the fabby's will disagree but linishers tend to roll the cutting edge and give too much back clearance.

I use the MSP (FIG 5) shape on pretty much all drills I sharpen. Fig 4 I would not use, when drilling it will be very hard on the flutes and wear the small edge away quickly, unless made from very high cobalt or solid carbide. A drill sharpened with a radius instead of a flat like Fig 4 can be used to REAM a hole to size, drilling a hole 0.5-1mm smaller will allow the drill to cut mostly on the flutes. Bigger drills can have more material left (smaller pilot hole) for drill reaming.

A finer grade wheel is good for sharpening drills, a sharp corner is very important for grinding web relief and other profiles on the drill point. CBN, cubic boron nitride, or artificial diamond is very expensive and really only good for fine tuning or touching up the cutting face.

Having a dressed and balanced wheel is also very important. Use the front of the grinding wheel too.