Chisel sharpening grit

[Tony Wilkins]

Rather than ask this on the Japanese chisel sharpening thread, I’ll start a new thread. Someone mentioned that chisels don’t need over 6,000 grit because an edge above that won’t stand up to chopping. What top grit do you use on chisels? Do you differentiate between chopping and paring chisels?

*sorry for another sharpening thread but was curious. Have a 6k king stone that was one of the first two sharpening stones I bought way back when but now have an 8k ceramic and a new 12k I haven’t used yet.

[Reed Gray]

Answers range from 400 grit to 30,000 grit, and every where in between. For sure, the most important part is to strop off the burr. Again, lots of variation. Cheap option is a bar of the cheap black stuff from a big box store, I use 3 in 1 oil on a piece of plywood, rub the stick on the plywood, and strop away. You can go to any leather store, especially one that makes saddles, and get leather scraps by the pound. You can get diamond pastes up to 16000, maybe 30000 now, not sure, and all the colored bars. In checking them out, color is not a universal grit code for them. The red jewelers rouge is very fine. Another thing to consider is jig or freehand. Most start with a jig. Stumpy Nubs, Rob Cossman, Matt Estella are people to watch, well some people to watch....

robo hippy

[Keegan Shields]

Someone mentioned that chisels don’t need over 6,000 grit because an edge above that won’t stand up to chopping. What top grit do you use on chisels?

I'm not sure I understand this advice. I have always read that the fewer imperfections (higher polish) an edge has, the better it stands up to use. Each micro-imperfection is a stress riser.

Given the extra force involved in chopping, it would seem that is when you'd see the most benefit from a higher polish.

[Rafael Herrera]

Your fine media, like your 6k or 12k stones, will refine the edge you obtained with the lower grit. I'd suggest you determine if it's worth the effort and time to go to the higher grits instead of just stropping and getting back to work. Some people like the ritual of going through multiple grits and spend inordinate amounts of time sharpening. A good practice is to use what you have and find out what you need to do to get an appropriate edge in the least amount of time. As an example, I use a washita stone when I need to refresh an edge. In all it takes me about 2 minutes or less, including stroping.

The edge fails as the apex wears out and/or breaks down. It's a skill to learn when to stop and re-sharpen before the damage is too extensive and you need to spend more time on the coarser stones grinding away the damage. Some premature edge failure is also due to not having removed all the previous edge damage. A jewler's lupe can help with that. When I need to remove damage I use a coarse stone first then go through regular sharpening.

Whether chopping or paring, you re-sharpen when the chisel stops cutting well, don't wait until the edge deteriorates too much.

[Michael Bulatowicz]

Rather than ask this on the Japanese chisel sharpening thread, I’ll start a new thread. Someone mentioned that chisels don’t need over 6,000 grit because an edge above that won’t stand up to chopping. What top grit do you use on chisels? Do you differentiate between chopping and paring chisels?

*sorry for another sharpening thread but was curious. Have a 6k king stone that was one of the first two sharpening stones I bought way back when but now have an 8k ceramic and a new 12k I haven’t used yet.

If a polished edge doesn't stand up better to chopping than a coarsely sharpened edge and doesn't cut better than a coarsely sharpened edge, one's technique likely needs improvement and/or maybe the edge wasn't actually polished.

My own chisel technique can certainly improve from where it is now, but I can still chop cleanly in soft pine with my chisels and the edges hold up well. The dovetails shown in the image were chopped with a Japanese "chopping chisel" (oiirenomi) with no sharpening needed during the effort; the edge was finished using my finest natural stone (a "broken-in" Dan's hard black Arkansas) which does a wonderful job of polishing the edge even though it's not traditional for a Japanese chisel (I don't own any natural waterstones).

You be the judge as to whether the edge held up to the chopping well enough in its polished state and whether it likely remained polished during the effort.
IMG_0056.jpg

As I always do, I lightly refreshed the edge afterward. I find that I spend less total time sharpening if I sharpen lightly and "often," particularly for chopping.

Not that it matters for the sake of this discussion, but I go with a full flat bevel on my chisels.

For chisels, I always polish the edge just as I do with plane irons--chopping or paring, the only difference is the bevel angle. There's no such thing as "too sharp" when it comes to any edged tool I've ever used.

[Jim Koepke]

Have a 6k king stone that was one of the first two sharpening stones I bought way back when but now have an 8k ceramic and a new 12k I haven’t used yet.

An old grit chart, that may have been deleted from my files, indicated my King 4k stone had the same size grit as my Norton 8K stone of 3µ.

Here is a different chart:

Abrrasive Grit Chart 2019.jpg

It may be that different makers stones with different markings, 6k vs 8k, may actually be pretty much the same.

My tendency would be to give the 8k & 12k stones a try and see if you like the difference in the edge produced.

In my experience, my 8k Norton produces a finer edge than my Black Arkansas, though the Black Arkansas produces a fine enough edge for most of my work.

jtk

[Tony Wilkins]

Here’s the quote from William Fretwell that I was thinking about:
“Up to 6000 grit for chisels is just fine, a 10,000 grit edge will last only a few mallet strokes longer. Plane blades do benefit from the extra effort to ‘polish’ the wood. In use, the plane edge acquires micro chips, I do mean microns. It continues to work very well for a long time, the micro chips still cut. I just strop the blade on leather and stropping compound to remove any small burr around the edge of the micro chips, then back to work.”

he doesn’t necessarily say he stops there. Another person says they stop at 3k for Japanese chisels in that same thread. It also says a more polished edge lasts only a few mallet strokes - longer. Missed the Longer in my fevered brain when. I read it the first time.

This isn’t necessarily going to change where I’m going to stop sharpening. I also skip between the 1000 and the 6, 8, or 12k stones*.
* I assume I’ll do that with the 12k but I haven’t tried it yet.

[Derek Cohen]

Rather than ask this on the Japanese chisel sharpening thread, I’ll start a new thread. Someone mentioned that chisels don’t need over 6,000 grit because an edge above that won’t stand up to chopping. What top grit do you use on chisels? Do you differentiate between chopping and paring chisels?

*sorry for another sharpening thread but was curious. Have a 6k king stone that was one of the first two sharpening stones I bought way back when but now have an 8k ceramic and a new 12k I haven’t used yet.

Tony, I do not enjoy debating sharpening discussions. Many simply have different experiences working in different situations and different conditions with different tool steels and different wood types. My observation is that working with hand tools is a combination of tool steel and tool technique.

I sharpen my chisels as high as I can (13000 grit) because sharper is better when one wants a cleaner cut. To illustrate, examine the end grain inside a dovetail where the waste has been removed. Is it relatively smooth, or are there large chunky holes where the wood has been torn away? An ultra sharp edge will be wasted if the technique using the chisel is lacking. An edge will not last long if it is being pounded into hard wood in too thick a slice. Thin slices are less damaging. Sharp edges and thin slices last a long time.



Regards from Perth

Derek

[Tom M King]

Regardless of what I'm going to use the chisel for, the sharpening stuff is right there, and it takes no noticeable time to go ahead and get it as sharp as possible. The total number of strokes past 6k is not many anyway. More seconds are spent deciding what the starting grit is than the few strokes on the finishing stones take. A lot of times for plane irons, the starting grit is 6k.

[Tony Wilkins]

Tony, I do not enjoy debating sharpening discussions. Many simply have different experiences working in different situations and different conditions with different tool steels and different wood types. My observation is that working with hand tools is a combination of tool steel and tool technique.

I sharpen my chisels as high as I can (13000 grit) because sharper is better when one wants a cleaner cut. To illustrate, examine the end grain inside a dovetail where the waste has been removed. Is it relatively smooth, or are there large chunky holes where the wood has been torn away? An ultra sharp edge will be wasted if the technique using the chisel is lacking. An edge will not last long if it is being pounded into hard wood in too thick a slice. Thin slices are less damaging. Sharp edges and thin slices last a long time.



Regards from Perth

Derek

That matches my thoughts (since over the years I’ve read and reread your bling and learned a lot, hardly surprising). Part of why that quote got me thinking is that I always want my chisels sharp and worry over them more than most of my plane blades.

[Chuck Hill]

I see a lot of mentions about it being necessary to remove the burr. I can see this for a paring chisel. But if you are chopping, won't the first chop remove it effectively enough?

[Derek Cohen]

I see a lot of mentions about it being necessary to remove the burr. I can see this for a paring chisel. But if you are chopping, won't the first chop remove it effectively enough?

Chuck, it depends on the steel and how tenacious is the wire. For example, A2 steel creates a tough wire. Over-doing the lowest grit on the primary bevel (such as the 100 grit stone), will also create a large wire, which will not necessarily be removed on subsequent higher grits. Now, if you force away the wire too aggressively, you risk damaging the newly sharpened edge.

Regards from Perth

Derek

[Chuck Hill]

Thank you Derek.

For those interested, Lee Valley has a good chart on comparative grits and the relevant micron size.
https://www.leevalley.com/en-ca/tools/grit-charts

[Reed Gray]

The debate still goes on in the lathe world, coarse grit= fewer teeth to get dull, fine grit = longer lasting because of more teeth, and a couple of variations.... If I had a lot of heavy chopping to do, I would want a more blunt angle on the cutting edge, like 30 degrees plus. For fine shavings and paring, then a more acute angle. You need a certain amount of metal to back up the cutting edge. Not enough and the edge bends over, too much and there is more resistance to the cutting.

robo hippy