Convex combo 8x3 Ark from Jarrod, arrived.

Discussion in 'Hones/Honing' started by kohalajohn, Apr 12, 2019.

    Not a huge difference in size, about the same size as all my hones which is good. Perfect hand holding size.

    Much thinner but that’s still ok. The w&b is shave ready but tugging just a little. Will take it to the black ark and see what happens.

  1. Good for you. Basil, it is a convex one?

    nice chopper there btw
    Last edited: May 28, 2019
  2. Yes it’s one of the convex ones from jarrod.
  3. ah good. hopefully you already have a flat ark to compare it to. I only have the convex, and am curious about what they say about convex being faster.

    This convex one just feels normal to me, which means that the flat arks must be very slow honing stones.
  4. I do not have a flat ark to compare it to. I am planning to slowly flatten the other side to have both surfaces to play with.
  5. Cal

    Cal Contributor

    :001_huh: Excuse my impatience, but why not quickly? :a30:
  6. Chan Eil Whiskers

    Chan Eil Whiskers Contributor Ambassador

    I have a Norton flat translucent and a flat hard black. The convex is, to me, easier, better, and faster. I think it's also more forgiving.
  7. Lol I have enough flat hones for now. Lol also I hear it will take a while to do.
  8. I drank the kool aid today
    However Separate stones, not the dual

    I’m not sure I am in love with the soft stone, it feels like a gravelly road could be my bad luck on the draw/ purchase, And I understand that rocks will differ rom each other. I’ll need to work on it more before passing final judgment, and look at it under magnification. The level of coarseness is not consistent throughout honing surface. It is a thirsty rock. do you just keep adding ballistol/water when honing?

    The hard trans black is a dream!!!
    I want a bigger one.
    A quick first run on it has produced amazing edge!!! (Dovo best quality)

    I’d be curious to see comparison of same flat stones vs convex... I’ll Lapp the flat sides later this week.
  9. Its a very interesting stone for sure.
  10. The enormous x-stroke is the best x-stroke.

    I feel like my flat arks are much faster than their reputation, but one is possibly an old Washita and both are pretty enormous so that could be why.

    The gravely feedback is pretty normal for a freshly lapped ark and will quiet down some with use. That’s one of my big questions with these convex stones is the break in period. No question my arks get better and better with use and infrequent simple green cleanings.
  11. If bevel is already set on flat hones, is it necessary to reset bevel on convex? Or will results be similar finishing on convex?
    What about taking previously finished edge, then just refinishing on convex?
  12. If set the bevel and then progresses on flat hones there is no need to reset it when going to the convex ark. If you use the convex ark to finish but then want to go to a different flat finisher you would need to spend some time to make the bevel flat again
  13. The math shows that the bevel angle will be reduced less than .1 degrees on each side, so technically the bevel will be reset before the stone can reach the edge. Depending on the bevel reveal (the bevel width) the amount of steel that needs to be removed to 'correct' the new bevel angle could be very small and within the ability of the convex finishing stone.

    The angle change of going to a large radius (33') convex hone from a flat hone is equivalent to lowering the spine .001". I worked this out a while ago but will I be rechecking my math.

    OK using a 33' radius convex hone and a razor with 6/8 between the contact points the angle change on each side would be .05 degrees. Equivalent to lowering the spine .0007". Ever measure tape wear while honing?
    Last edited: May 29, 2019
  14. Cal

    Cal Contributor

    :001_huh: I'm confused. Where does the 33' radius come from? Jarrod talks about a spherical surface equivalent to that of an imaginary 20' wide basketball (which would obviously have a 10' radius).
  15. SliceOfLife

    SliceOfLife Contributor

    Arks don't remove much material without serious pressure... and even with serious pressure, it's not extreme. What a convex does is let you use serious pressure, without applying it. Instead of applying your usual, say 200g of pressure in an ~1cm², you apply the same pressure on, for instance, 0.1cm². Same principle as a very narrow hone or a rod sharpening system. You could accomplish the same (with a flat razor and assuming the estimates for area I invented were accurate) with 2kg pressure on a flat stone. The convex and/or narrow hone remains useful in its ability to relatively simply deal with razors which aren't flat, but then guys will argue that flat hones corners or sides would work just as well with practice.
  16. Ok. Math is not my forte. But my understanding is that jarrods master sagitta is 5cm on a 12 inch tile/ diameter. Curious what would be the equivalent sagitta for 9 inch diameter.
  17. The 33' radius was calculated from a .5mm crown over an 8" hone which is one the figures floating around.
  18. Where did you get this? Every thing that I have seen has been 2 orders of magnitude smaller. I've been using .5mm over 8" for my calculations. A tile is only about 1cm thick!
  19. Cal

    Cal Contributor

    :laugh: Figures "floating around" ain't that helpful are they? In Jarrod's scheme of things (with the 10' radius) the crown would be ~1.7mm. Quite a difference (but still pretty tiny).

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