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Learning to Sharpen #6: Highest Grit for Sharpening?

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Blog entry by Mark Colan posted 08-12-2013 12:50 PM 935 reads 0 times favorited 4 comments Add to Favorites Watch
« Part 5: Sharpening Class: chisels Part 6 of Learning to Sharpen series Part 7: Sharpening Class: Cabinet Scrapers »

How high a grit one should one use when sharpening? Some people sharpen with a 1000/8000 water stone. There are 12000 and even higher grit stones out there – though I have learned that the grit rating scheme is not always consistent, so that a 12000 is not necessarily finer than a true 8000, for example.

In the class I took this weekend, the grits were: 220 400 1000 2500. For a chisel whose back was not flat, and 220 was taking too long, the teacher suggested 120 or 150. And for damaged chisels (one with a chip in the cutting edge), I used a 36-grit wheel on a 1200 rpm grinder. The latter, when taken through the paces, yielded a beautiful looking, but more importantly, SHARP chisel.

A reason for going to 2500 or higher is the satisfaction of the nice mirror finish, but I’m not convinced that it makes a huge difference in cutting wood, and I doubt it makes the edge last longer.

Before taking the class, I occasionally used a cheap combo stone that I bought at a Chinese restaurant supply, really intended for kitchen knives. The two grits are probably in the range of 200/400, and I have always used it dry. It does not provide a mirror finish or anything close, but it did greatly improve the usability of my chisel, without going to higher grades. And I sharpened only the bevel side, because I didn’t know better.

Now that I know better, I am certain I will get a better edge, but it will be at the cost of some additional effort. With sharpening, there is this law of diminishing returns, where additional effort does not give that much improvement. For me, I am looking for the sweet spot between not too much effort and yet sharp enough for my purposes. But it isn’t much extra effort to go to a higher grit or two than necessary, and it looks sweet when you do that, even if the additional sharpness is mostly theoretical after the first use.

-- Mark, hack amateur woodworker, Medford (greater Boston) MA



4 comments so far

View waho6o9's profile

waho6o9

5066 posts in 1262 days


#1 posted 08-12-2013 01:55 PM

https://www.youtube.com/watch?v=WO_M95qDdAQ

Nice blog Mark, thanks for posting.
A sharp edge is the only way to work, how you get there is great learning curve.

Oh yeah.

View Mark Colan's profile

Mark Colan

209 posts in 1530 days


#2 posted 08-12-2013 02:00 PM

Oh yeah. Great learning curve indeed. I’m still on the sharp rise of that curve! Thanks for your comment.

-- Mark, hack amateur woodworker, Medford (greater Boston) MA

View rad457's profile

rad457

202 posts in 491 days


#3 posted 08-13-2013 01:16 AM

Taking some classes at the Inside Passage School and the system. I was taught/shown, flatten/lap back with
180 grit sandpaper on a flat surface, (cast or granite) set the bevel angle (hollow grind) on hand powered grind wheel 80 grit, then hone with 1000 wet stone followed by 8000 polish (mirror finish) Amazing results on chisels and plane blades. Going to try and post some pictures of the Kernov planes we built.

-- Andre of Alberta. Are you Kidding me?

View Mark Colan's profile

Mark Colan

209 posts in 1530 days


#4 posted 08-13-2013 03:04 PM

The teacher for the class I took said he would prefer to use a hand grinder, but did not have one.

For new blades, honing the bevel with 1000 and 8000 may be enough, after you use the grinder to set the bevel angle and create a hollow up to the edge. Grinding with 80 seems safer than 36, but also takes longer.

For the back, though, I think going 220-400-1000-1200 is necessary for some chisels, especially ones that have seen hard use or misuse.

-- Mark, hack amateur woodworker, Medford (greater Boston) MA

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