Sharpening with the King 1k/6k combination stone

This report illustrates a sharpening progression inspired by techniques demonstrated by knife maker Murray Carter in his straight razor honing video:

This series of images is particularly effective in demonstrating the differences between edge leading and edge trailing strokes.  A technique for burr removal is also illustrated.

First, a comparison of edge-leading and edge-trailing sharpening on the King 1k stone, starting with edge leading:

GNV_K1k_EL_11

Edge-view of the apex following edge-leading strokes on the King 1k stone. A micro-chip is visible in the foreground and a burr in the background of the image.

GNV_K1k_EL_13

Edge-view of a cross-section through the apex following edge-leading strokes on the King 1k stone. The white lines show the native angle of the blade with a burr clearly visible beyond that triangle. Such burrs form when the micro-chipping occurs more slowly than metal removal from the bevel faces.

GNV_K1k_EL_20

Side-view near the apex following edge-leading strokes on the King 1k stone. A still-attached micro-chip is visible left of center.

Next, edge-trailing.  As expected, edge trailing strokes on the King 1k leads to the formation of a foil-burr.

GNV_K1k_ET_01

Edge-view of the apex following edge-trailing strokes on the King 1k stone. A burr has formed since micro-chipping of the apex does not occur with any frequency under these conditions.

GNV_K1k_ET_04

Edge-view of a cross-section through the apex following edge-trailing strokes on the King 1k stone. The white lines show the angle of the blade near the apex (10 degrees) is significantly less than the native angle (16 degrees) indicative of a foil edge.

Moving to the King 6k stone, first with edge-leading strokes. The apex micro-chips faster than the bevel is abraded preventing the formation of a burr.

Surprisingly, edge-leading strokes on the 6k stone have reduced the keeness of the apex as compared to edge-leading strokes on the 1k stone in this example. Although the scratch-pattern is finer, this does not correlate to an improvement in keenness.  Swarf and loose grit may play a role in this process, as suggested by the second image below.

GNV_K6k_EL_01

Edge-view of a the apex following edge-leading strokes on the King 6k stone. Both swarf and abrasive debris are visible. A burr is not evident.

GNV_K6k_EL_05

Edge-on view of the apex following edge-leading strokes on the King 6k stone. A significant quantity of debris, particularly curls of swarf, has collected on the apex when blade was rinsed after honing.

The above progression was repeated under running water to determine whether continuous flushing of swarf and slurry improves the keenness with achieved with edge-leading strokes on the 6k stone. The image below shows no improvement.

GNV_K6k_EL_RW_07

Edge-view of a cross-section through the apex following edge-leading strokes on the King 6k stone performed under running water. There is no significant reduction in the amount of apex-damage due to micro-chipping. The blade is significantly less keen than that achieved with a the 4k Shapton glass stone.

GNV_K6k_EL3_06

Side-view image of the bevel following edge leading strokes on the King 6k. Damage to the apex is evident in the disruption of the stria in the last 10 microns of the bevel.

Next, to edge trailing strokes on the 6k stone.  Once again, edge trailing strokes lead to the formation and growth of a foil-burr.

GNV_K6k_ET_01

Edge-view of the apex following edge-trailing strokes on the King 6k. A substantial foil-burr is present, easily visible even with an optical microscope.

GNV_K6k_ET_03

Edge-view of a cross-section through the apex following edge-trailing strokes on the King 6k. A substantial foil-burr is observed.

The technique described in the embedded video should be expected to produce a standing burr beyond the apex. The next step is to cut into a piece of soft wood several times and observe the effect on the burr. The images demonstrate the result in this example.

GNV_K6kET_rwood_01

Edge-view of the apex after a three light draw-cuts into a piece of redwood (across the grain). The large foil-edge burr is folded over 180 degrees.

The burr above was relatively large and easily folded. The progression was repeated, to create a more subtle burr, shown below.

GNV_K6k_ET_smlburr_05

Edge-view of a cross-section through the apex following edge-trailing strokes on the King 6k. The procedure was performed to produce a minimal-sized burr.

Cutting into a piece of redwood with the smaller burr also causes it to fold over.

GNV_K6k_ET_smlburr_redwood_08

Edge-view of the apex after a three light draw-cuts into a piece of redwood (across the grain). The small foil-edge burr is folded over approximately 90 degrees.

It may have been expected that the burr would be torn off; however, even at the location of a chip, where the burr could be expected to engage the wood, there is no evidence of the burr tearing off.

GNV_K6k_ET_smlburr_redwood_09

Edge-view of the apex after a three light draw-cuts into a piece of redwood (across the grain). The small foil-edge burr does not break off, even at a chip, although swarf is observed to accumulate at that point.

The next step in the procedure is to perform a few edge-trailing strokes on the 6k stone. As an aside, the three images below show the effect of going directly to stropping on a single sheet of newspaper on the 6k stone.

GNV_K6kET_redwood_newspaper_01

Edge-on view of the apex after stropping on newspaper. The folded apex is broken off leaving a 1-2 micron wide “flat.” One small “tooth” of unbroken apex is visible in the background.

GNV_K6kET_redwood_newspaper_03

Edge-on view of the apex after stropping on newspaper. The folded apex is broken off leaving a 1.5 micron wide “flat.” Burnishing from the newspaper stropping is visible, particularly on the left side of the broken-off apex.

GNV_K6kET_redwood_newspaper_04

Edge-on view of the cross-section through the apex after stropping on newspaper. Burnishing is visible on corners of the broken-off apex. Debris is visible in the hollow between the two burnished corners of the apex.

Returning to the procedure (as described in the video) another blade was honed and a small burr was formed with edge-trailing strokes on the King 6k, the burr was folded by cutting into a piece of redwood. The blade was then given 3 edge-trailing strokes on the 6k stone to break-off and/or stand-up the burr.

LC_6kET_redwood_6kET_01

Edge-view of a blade that has had the burr folded by cutting into a piece of redwood. The blade was then stropped on the 6k stone to break-off and/or stand-up the burr.

LC_6kET_redwood_6kET_02

Edge-view of a blade that has had the burr folded by cutting into a piece of redwood. The blade was then stropped on the 6k stone to break-off and/or stand-up the burr. The residual burr does not appear well attached to the apex.

The blade was then stropped on a single sheet of newspaper wrapped around the stone (6k side up). The residual burr is effectively removed by this step.

LC_redwood_6kET_newspr_01

Edge-view of a blade that has had the burr folded by cutting into a piece of redwood. The blade was then stropped on the 6k stone to break-off and stand-up the burr. Finally, the blade was stropped on a single sheet of newspaper set on the 6k stone to clear away the residual burr fragments.

LC_redwood_6kET_newspr_02

Edge-view of a blade that has had the burr folded by cutting into a piece of redwood. The blade was then stropped on the 6k stone to break-off and stand-up the burr. Finally, the blade was stropped on a single sheet of newspaper set on the 6k stone to clear away the residual burr fragments.

LC_redwood_6kET_newspr_04

Edge-view of a cross-section through the blade following the competed progression. A significant increase in near-apex angle is produced (from 18 to 36 degrees) .

LC_redwood_6kET_newspr_08

Edge-view of a cross-section through the blade following the competed progression. The increase in near-apex angle (from 18 to 36 degrees) results from deformation of the apex during the burr-folding step.

At this point, the blade easily passes Murray’s 3-finger test. The blade effortlessly draw-cuts paper and push cuts with some effort. Scrape-shaving arm hair can be achieved, but it does not catch hair above the skin. This is an excellent working edge for a knife but I have failed to produce a “shave-ready” straight razor by this technique.  It appears that the greatest variable in this progression is the amount of metal removed during the post-wood-cutting step of edge-trailing strokes on the 6k stone.  A few more strokes or greater pressure may have been beneficial.

Finally, the blade was stropped on a chromium oxide loaded horsehide strop, laying flat on the 6k stone.

LC_redwood_6kET_newspr_cro_01

Edge view of the blade following stropping on a chromium oxide loaded horsehide strop laying flat on the 6k stone.

It appears that the apex does not make contact with the strop on the right side and that the improvement is minimal. Perhaps a thicker, more compressible strip of leather would have a greater effect.

The above results should not be generalized to predict the capabilities of this sharpening technique.  In particular, this blade was sharpened at a fixed angle, precluding the advantages of increasing the angle by freehand sharpening (making better contact with the apex).  Also, low-angle straight razor blades will be deformed to a greater extent by the burr folding step than a 30 plus degree (inclusive) knife blade would be.

Advertisements

15 responses to “Sharpening with the King 1k/6k combination stone

  1. Fantastic job! And kind of scaring as well…
    I was hoping that the edge-leading 6k was a lot keener than the edge-leading 1k, but empirical tests show I was wrong.

    Like

    • I tried a number of approaches, but could not achieve any reasonable level of keenness in the edge-leading direction from this (6k) stone. The combination of a slow stone with loosely bonded abrasive means that micro-chipping exceeds bevel-face abrasion.

      Liked by 1 person

      • Thanks for this extensive investigation. I feel that I wouldn’t have either the patience, the gear (electronic microscope, extensive stones and blades array, you name it), or the knowledge.
        Of course the quantity of variables is huge. I still can’t understand the “pyramid” system for stone grits when honing straight razors. Hand pressure plays a lot as well.

        Like

  2. Thanks for sharing this. I’d love to see you try the following: edge trailing with the coarse stone at a lower angle, then edge leading with the fine stone with very light pressure and an angle 2-3 dps higher, then stropping on a compressible material at the lower angle.

    Like

    • That would be much easier with a complimentary Wicked Edge 😉

      I have done this with a straight razor, adding several layers of tape to increase the angle from 8 to about 12 degrees.
      The problem is that the contact area becomes very small, and even with the lightest touch the lateral pressure (force/area) is very high.
      With the low angle straight razor, the apex is pushed to the side and the 1k burr grows rather than being removed. This is essentially why micro-bevels don’t typically work with straight razors. I suspect that at sufficiently high sharpening angle the burr will break rather than flip, but I have no evidence.
      I have not seen a clean leather strop remove a burr near the sharpening angle. A linen strop will, with abrasive.

      Liked by 1 person

  3. This stuff is great. I’m still amazed by the plasticity of steel at that scale. The difficulty of getting a perfect edge is a bit depressing–but at least I have a better understanding of what I’ve been up against.

    Incidentally, if you ever get your hands on a Spyderco stone I’d love to see the surface and results!

    Like

  4. Great stuff once again Todd!!

    Any idea why, when you draw the edge through the rosewood, the burr is all folded over one direction? I would expect it to be every which way.

    I have been playing around lately w/ using only diamond lapping films on razors, all the way until the strop progression. I am guessing the micro-beveling of the apex on a razor may react different w/ different stones/backing probably – this method seems to produce a nice shave so far but i have more experimenting to do!!

    So, if finishing a razor edge trailing on say a shapton 15k, would it be recommended to start w/ edge leading, then switch to edge trailing for a few passes to remove the micro chipping and create a keener edge, before the strops?

    Like

    • It seems that with a continuous burr, once it starts rolling in one direction it continues to that side for the length of the blade.

      Lapping films are compressible, and can produce some convexity (usually 1 or 2 degrees) in the bevel at the 3 micron stage. In this case, micro-bevelling (or putting wet paper under the film to make it more compressible) actually just brings the apex into contact on the 1 micron film.

      If you are stropping on a “loaded” strop, a new apex is formed, so the finishing strokes at the 15k level shouldn’t be significant. If you were going directly to clean leather, 1 or 2 edge-trailing strokes likely produce a noticeable effect.

      Like

  5. OK…so what I think I understand after my year of online study is:

    1) The edge is a delicate thing.
    2) Sharpening on a hard uneven stone will lead to micro chips. (so I ought to finish on something more delicate).
    3) Trouble is…I can’t do edge leading on leather, and edge trailing always leads to foil burrs.

    Would it be crazy to dedicate one of my Spyderco stones to edge leading stropping
    w/ a thick-ish layer of Chromium Oxide III ?

    Like

    • Yes, the edge is delicate compared to a stone.

      There are many ways to sharpen a blade. In the particular the case of edge-leading strokes on waterstones (Shapton, Naniwa, King, etc) the apex will microchip rather than form a burr, and the size of those chips decreases with the size of the abrasives. For example, on a 20k stone, the chips are on the scale of 0.1 microns – creating a very keen edge. So, one approach is to progress to a high grit stone. Another approach, on a coarser stone, would be to finish (after edge leading strokes) with a handful of edge trailing strokes, increasing keenness, but stopping before a burr forms.

      Stropping does not always lead to burrs. Provided the strop “wraps-around” and forms a new, clean apex, there will be no significant burr. The challenge is that we can’t easily remove a burr from the side, it just flexes away, like trying sharpen a sheet of aluminum food-wrap foil.

      Like

  6. Excellent! I took Murrays 500 course several years ago, I use a similar method and can achieve tree topping with just the 1000/6000 and newspaper. I would love to see what my edge would look like with your equipment!

    Like

  7. So to use this information practically (for knife sharpening in my case) it seems you should work up to edge trailing on the 6k, run over the wood, a few more edge trailing on 6k, strop on newspaper. Is there a maximum amount of those last edge trailing on the 6k you should do? Basically, is another burr created if you do too many extra edge trailing on the 6k after cutting into the wood, and if so, do you know how many strokes you used? Additionally, can you over-strop on the newspaper? Again I’m trying to get an idea of whether I should be doing 50 strokes or 2 strokes per side.

    Like

    • After re-reading the article I saw that you listed 3 edge trailing strokes after the wood cutting, and that more may be beneficial. Should’ve read more carefully! I’d still be interested in hearing approximately how many strokes you used on the newspaper, if you remember.

      Like

    • Most people will prefer a knife have a better draw-cutting than push-cutting performance. Forming and breaking off a small burr is an easy way to achieve that sort of edge. The idea is to fold the burr by cutting into the wood and then breaking it off by stropping. For a knife, we don’t really want to restore keenness, but instead leave that rough/broken apex.

      Generally, stropping on softer substrates does what it will do within a couple of laps and not much changes for the next few hundred. As a habit, I always do 30 laps, but that is really an arbitrary number.

      Like

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s