Edge Life based on Abrasive - A proper thread


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24 Aug 2015
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Since this got another thread off of the rails. This isn't a treatise on making for a complicated sharpening method (the best may actually be the cheapest - short and long term).

It's the oft-said advice that everything will make a tool last equally long and be equally sharp. That's not true, and it's been tested twice, at least - and I'm sure it's actually been tested more like a dozen times.

The standard for getting an edge is getting the shape of it, then polishing the very edge. The sensible way of doing this (and the laziest) is to use a medium abrasive off of a ground edge, remove any remaining wear if the edge isn't reground, and then polish just about the smallest amount that you have to. If you use something like diamond on wood (which will cost you only a few dollars), it replaces a leather strop.

For the purpose of actually seeing the results from doing this (which were obtained in a test used for another purpose), the number of feet planed (in beech) using an O1 iron and various media (same plane, finished edges viewed through a microscope to confirm wear and defects removed, etc), the results were as follows (feet planed before a plane failed to stay in a cut):

1 micron diamond finish: 840 feet
dan's black ark (the finest I know of, new or old): 700 feet
5 micron diamonds (about 2 to 3 times as fine as a settled in 1200 grit ezelap): 568 feet

After a rerun to confirm results in a second piece of wood (5 micron test omitted, it was far less pleasant to plane with to say in the least):

1 micron diamond finish: 908 feet
dan's black ark: 738 feet

Strangely similar relative comparison, and the test was ceased. 2.5 micron diamond results, I cannot find, but they were only slightly better than 5 micron.

Loose diamonds were tested on a precision cast plate (not a plane sole or anything with significant defects).

The point here is important. If you are woodworking, you have to be able to sharpen. Once you're able to sharpen, you are wise to do better at it and sharpen to a finer level (without introducing extra time) because your results will improve and your effort in getting them will lessen. You will also be well set up to move on and sharpen things other than straight plane irons and chisels.
What's the other virtue here in terms of results? Economy.

A single diamond plate or middle stone of any type can be followed on wood (or cast if you have the means), etc. 1 micron diamonds are about $10 for 25 carats. and a little more for $100 (found as "loose diamonds" on ebay or anywhere else that doesn't gouge).

Why else do I think this is important to understand? There are exceedingly few workers who use hand tools only. The two that I know of, instead of quicking their sharpening once they started doing all of their work with hand tools went finer instead. It's a path to follow, no matter the vehicle you use to get the steel to the stone.

It's misleading to suggest to anyone (new or old) that it takes longer, makes no difference or doesn't yield anything.

Steve Elliot also did a much more rigorous version of this probably more than a decade ago. He found that he could add steps and improve feet planed further (and with some kind of contraption, managed to show sharpness was better at each given footage). I chose not to test further because adding steps isn't something I wanted to do.
how do you know that your feet amounts are correct? what I mean is isn't that a subjective concept? one persons sense of a blade dulling is different to another one, it's very hard to quantify, and in reality when working with real wood (not talking about it actually working it with my hands) I just feel for when it's dull, then sharpen up again, no need to write a 10,000 word dissertation on the subject unless you actually are a well respected academic, nobody cares. :lol:
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