Well the new toy arrived but via USPS instead of the UPS girl.
The system is simplicity, a calibrated 'string' and scale to measure how much force it takes to cut the string. The unit I have has a 5 gram resolution, for a few dollars more you can have one with a 1 gram resolution. I figured 5 grams is close enough for my use. I haven't found anything on repeatability or range of error but with running several test on the same edge it seems to fall within a narrow range of results of about 5-15 grams difference maximum. Most of the time within 5 or 10 grams raw numbers.
The chart of "common edges" lists a double edge razor blade as taking 50 grams to cut the test string, a high end knife as needing 300 grams, and if it takes more than 400 grams the edge needs sharpening.
First the good news: Stropping with 'green stuff' on leather will lower needed force by about 40 to 50 grams. While it will take more tests to confirm, the type of stone makes little difference. I sharpened chisels from the same maker on Spyderco, Ark oil, and Shapton glass, all three before stropping took around 200 grams to cut the test string. And all three after stropping were in the 150 gram range.
Maybe the most surprising result was I ground one chisel on the Tormek to 25 degrees and then sharpened using the LN jig set for 30 degrees. While it was within what I suspect is the margin of error before stropping it took 20 grams more force to cut the test string than a chisel sharpened freehand on the same stone. After stropping the difference was 5 grams.
Will the toy make a difference in woodworking....not much but now I have a way to quantify sharpening technique. Is it better to strop, or not and gives a way to test longevity of different sharpening methods such as the same old question does a stropped edge last longer than one that is not.
I know what I've found and believe over the years but now I can put numbers to it instead of just 'because'. And maybe it will show me where I've been wrong as well.
Anyway bottom line a fun little toy and a lot cheaper than an ESM.
What is the toy Ken? Is it covered under NSA rules or can you post a pic of?
ReplyDeleteRalph,
ReplyDeleteHere is a link to the web site: http://www.edgeonup.com/
It has been fun to play with. Like I posted there are some interesting results from checking at various stages of sharpening and stone vs. stone. I haven't got into different steels or makes of chisels yet but I expect the results could confirm or disprove some of my basic beliefs.
So far the most eye opening is there is little difference between freehand and using a jig and how much difference stropping on leather with 'green stuff' makes. I will test bare leather as well as oiled leather along with other strops as well.
Stay tuned more to follow,
ken