Tuesday, December 10, 2019

Thoughts on Sharpening

OK hip boots are on and I'm ready to walk if not run into the swamp. First my steps and equipment  are what I've found work with the type of steel used in my shop. I'll start with something I think most will/should agree with. Sharpening is a three step process, grinding to a sharp edge, honing to improve the the edge, and finally polishing to smooth out the scratches left by the first two steps.

While I will grind using a rotary grinder when the edge needs major work most of the time I grind with "stones". While I've used different makes of diamond "stones", synthetic water stones, and sand paper on something flat, my most used are either a course or medium Norton India stone. The India stone is reasonably fast stays flat and is cheap. The medium India's scratches are easy to address with a honing stone and the India gives a burr you can feel but is easy to remove on your hone.

My hone depends on the type of cutter. If I'm sharpening western steel most of the time I will hone on a Pike "Lilly White" Washita. With Japanese chisels my honing stone will usually be a Tsushima Nagura. One of the reasons to change to JNats when sharpening Japanese chisels is to preserve the definition between the hagane (hard steel) and jigane (soft steel), that preservation is mostly out of tradition but shows a well sharpened chisel with a perfectly flat bevel.

One of the advantages or maybe disadvantages of oil stones over water stones is in the burr. With oil stones even at the level of polishing you can feel the burr, with water stones, I think mostly because of the "slurry" developed in use, not so much. With water stones knowing when the edge is sharp depends much more on sight vs. oil stones sight and feel.

The last step is polishing. For western steel I have a very special Black Arkansas (not all Arkansas stones are equal). Polishing on a Arkansas stone is a two step process that also may use a strop. First you need to polish to remove the scratches left by the honing stone then "chase the burr" to remove the wire edge. A strop can aid in final polishing.

For Japanese chisels I polish on one of several JNats depending on the level of polish needed or wanted. Whichever stone that is used it is the final step because a strop will obscure the definition between the hagane and jigane.

Because I do not use some of the more difficult steels to sharpen such as A2 I will normally sharpen to a flat bevel. The exception is when I re-grind using the Tormek but that bevel will soon return to flat. I'm not a fan of "micro" bevels.

A side note, synthetic water stones can be very fast cutting and give a much "shinier" surface. That shinny surface can be deceiving and not be as polished as a duller looking surface left by a Natural stone.

Notice no mention of free hand vs. jigs because in the end it makes no never mind. I free hand because I find it faster and easier but, as always, YMMV.

ken

11 comments:

  1. One consideration I didn't see anyone ever talk about when doing the sharpening chat was the workshop/shed itself - so I use diamond stones myself, not because they're better than anything (I don't sharpen enough to realise the full potential of any sharpening system because I'm lazy :) ) - I use them because nothing else will fit in my shed. There's no room for the water baths and storage space and so on that waterstones need, or to store all the sandpaper and lapping mediums and a surface plate, and by the time I learned enough about oilstones to think I might get away with one and the mess from its slurry, I'd already gotten the diamond stones. They're inset into one board (the same setup that paul sellers did a video about) and that board just gets shoved under the bench on top of the thicknesser when not in use, which is the one 10"x1" slot I could find for it. I mean, I'd love a tormek T4 or a sorby proedge, I'd love a dedicated sharpening station, but there's just no room.

    Never seen that in a sharpening talk till I hit it nose-first though :(

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    1. Mark,

      Because of the type of scratches diamonds leave they do not make a good hone or polishing stone. That said, there are ways to work around their faults.

      Oil stones are not that messy, I keep my oil stone holder in a low cake pan but even that is a little overkill. Water stones are another story, there is no way around the water stone mess.

      ken

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  2. I like the "...I'm no fan of micro bevels". I still don't see the need for them.

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    1. Ralph,

      I can see using one if your cutter is A2, but both are sub-optimum in my opinion.

      ken

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  3. Sticking your neck out on sharpening :-)
    Probably the most debated act of woodworking on line and everywhere else.
    That said, whatever works for you stick to it. Methods do not matter, it's what works for you that does. For the record, I do similar to you, except I am more inclined to use my side clamping jig, but yes, I know and do free hand also.

    Keep up the sharp end, its a never ending battle

    Bob, with a sharpening marathon coming up on the horizon

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    1. Bob,

      I figured with all the motorcycle posts I needed something about tools or wood :-).

      I have no problem with using jigs but marathons I can't handle :-). If I do more than a couple of cutters at a time the third or later don't really get sharp, maybe kinda shinny but pure luck if sharp.

      ken

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  4. Steve D7:14 AM

    I was going to ask you a question about the JNats some time ago and was waiting for a sharpening post to ask. I've since forgotten my question.

    It had something to do with the breakdown of abrasive and whether multiple blades get processed together or individually but I don't remember. I can imagine what this will be like when I'm your age ;)

    I grabbed a plane with an old unsharpened (by me) blade that was out of square and a shallower angle than what I use. One side of the bevel got eaten by the stone while the other side took forever to reach the other corner. It ended up as a hybrid full bevel / micro bevel edge. What's the justification for wasting the extra metal to make it full bevel across? I was trying to get something done as opposed to hiding from the wife.

    If you freehand sharpen thin irons you are adding more microbevel than a LV guide imparts, it's just harder to see.

    There, took the bait.

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    1. Steve,

      I do not normally do "batch" sharpening, even when I have a new set of chisels. I'll work the chisels one at a time, do one go do something else in the shop before picking up the next chisel maybe even a few days later. While I enjoy sharpening, there are limits to how much I enjoy it :-). So I do not have an answer to your "maybe" question.

      I have no problem with getting a working edge that is not flat yet. Happens every time I need to grind with a rotary grinder but as I work the bevel and re-sharpen the bevel will eventually become flat and I try to keep it that way. BTW, I've been know to hide from the wife as well and sharpening is a great way to do it.

      Could be, but I think how much depends on how you work the stone.

      ken

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    2. Steve D6:18 AM

      If you are planing that might invite company and conversation but sharpening seems boring enough and intense that a wife will just keep walking. Wearing magnifier devices will render the sharpener goofy enough that chitchat is extremely unlikely.

      I'll remember my question when it's thoroughly off topic.

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  5. Anonymous3:01 AM

    I am in the same situation as Sparks.
    I have two double sided diamond plate (extra-coarse/coarse and fine/extra-fine). I usually only use coarse, fine and strop. I have used extra-fine to polish the back side. I don't know what I might be doing wrong but extra-fine doesn't give me better results on the bevel.
    Now this is for woodworking, not to shave my face (although I sometime test on my arm). So i have in mind this:
    https://paulsellers.com/2013/11/sharpness-mean-real-terms/
    Sylvain

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    1. Sylvain,

      I've read that post before and for the most part agree with it. Going past a Washita grade stone doesn't improve the iron's ability to work wood but can improve the working life of the cutter by polishing/smoothing the scratches left by the honing stone.

      I like to use a polishing stone but truth is I could get a good cutting edge with nothing more than a honing stone like a Washita and a strop.

      I expect if you finished your bevel with the extra-fine and a strop vs. the fine and a strop the only difference might be in the life of the working edge and with that there are so many variables I also doubt you could tell.

      ken

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