Hand Tools Archive

Subject:
Experience that refutes your assumption
Response To:
Re: diamond paste plate ()

Bill Tindall, E.Tn.
When I was researching how to abrade (sharpen) abrasion resistant tool steels the universal recommendation from abrasive manufacturers was to use diamond. For a given grit size nothing cuts faster. Comparing diamond to aluminum oxide, the most common abrasive used by woodworkers for sharpening, the difference is huge. But, as you imply, there are factors in addition to rate of material removal that must be considered in judging the overall time to sharpen a dull tool. What several years experience in my shop has demonstrated is that fresh loose diamond charged onto cast iron cuts any steel used for woodworking tools blazing fast.

The problem to be solved is how to use loose diamond on cast iron the most effective way. Some will disagree, but my experience and that of machinists who have used this technique for decades has concluded that there is carryover of coarser particles to the subsequent plate used for the next finer size abrasive. Plate contamination will eventually require resurfacing the plate. Grit carryover, if you believe in it, limits the use of loose diamond to one grit size in a sharpening sequence. So, where is the best place to use this one opportunity to use diamond paste to cut really fast?

Back flattening, old tool pit removal, and other "high volume" material removal needs are a substantially different topic than sharpening a dull plane blade. I can describe the use of loose diamond for these annoying tasks if there is interest. The technique uses much coarser particles on plastic substrate.

My tool sharping arsenal incudes a grinding wheel employing a soft bond pink aluminum oxide wheel, various cast iron plates and diamond pastes, a grade "fine" fixed diamond plate and leather charged with the green stick.

For years I hollow ground on the wheel as needed, refined the edge on the fine fixed diamond plate and finished up with 1 micron diamond on cast iron. This approach easily meets your 10 minute target even for a very dull edge on a highly abrasion resistant tools steel like CPM 3V, M2, A2 or one of the 440 high performance steels. The problem with this sequence is that the highly effective loose diamond is being used in the place where speed is least needed. Also, for my needs, it may not be necessary to refine an edge to 1 micron.

To that end I have been experimenting with using some grit size of loose diamond after hollow grinding followed directly by green stick on leather. I have not come to a conclusion of what loose grit size is best but it will be around 10 micron +/-. Also I have not come to a conclusion whether this new approach is preferred. I hope others will experiment with this use of diamond paste.

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