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Grit angle change

This topic contains 48 replies, has 5 voices, and was last updated by  NorCalQ 01/15/2019 at 1:49 pm.

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  • #48309

    Drew
    Participant
    • Topics: 11
    • Replies: 72

    100/200, paddle 2

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    #48313

    Drew
    Participant
    • Topics: 11
    • Replies: 72

    … it won’t let me post the last orange bottom reading picture. It reads zero, on the money.

     

    Marc, looking dead on the point of the knife, the spine is clamped slightly left of center. It’s sitting more on top of the left vise-pin.

    #48314

    MarcH
    Moderator
    • Topics: 58
    • Replies: 1855

    Thanks for the effort, Drew.  As you said it’s a hard and crude method to employ when dealing with 0.25º<>0.50º which are very tiny differences and especially using the AccuRemote digital cube which isn’t always the quickest meter to settle in and lock, and juggling everything like you did.  Allowing for molding imperfections in the plastic handles and the difficulty using this method I don’t see anything that is really so far off that you can’t still get good results with attention to detail and good technique.  You may have to play with your finger position and pressure or flip the stones end for end or side for side to find the orientation that gives you the best uniformity.

    I still think the offset knife may be the biggest contributor.  I’d like to see you measure the distance the clamped knife edge is from a vertical.  Done consistently from side to side.  Measuring the flat side of a relatively narrow nonuniform rusted file knife isn’t really telling. IMO.

    Marc
    (MarcH's Rack-It)

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    #48315

    MarcH
    Moderator
    • Topics: 58
    • Replies: 1855

    … it won’t let me post the last orange bottom reading picture. It reads zero, on the money. Marc, looking dead on the point of the knife, the spine is clamped slightly left of center. It’s sitting more on top of the left vise-pin.

    If the knife is off center that explains the different is the bevel heights seen with the marker when both are set at 15º.  It won’t give you uneven bevels.  Un even bevels are when a centered knife is sharpened with two different angles for each side.

    Your 15º angle is contacting the knife at two different height positions on the bevel. If you removed enough steel eventually that the bevel finally apexed the edge then you would see uneven bevels.

    Marc
    (MarcH's Rack-It)

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    #48316

    Drew
    Participant
    • Topics: 11
    • Replies: 72

    I’m just not convinced. Regardless of how the knife is positioned in the vice, if it’s locked in tight and ground fresh, with no movement in it, that angle of bevel should contact the stones the same, whatever grit I use.

    Everything is consistent, that I can tell, besides the stones.

    Are you saying that this system will only work putting consistently angled bevels on steel with a knife clamped at 0.00 vertical from base?

    I did remove steel to apex, each grit. I don’t mind uneven bevels, as long as the entirety is mirror polished and able to shave neck hair.

     

    Let’s say I did take the knife out, straighten it up 0.00, (I’m not sure what I can do for the left-placed LAA, that may just be the way it is), regrind at 100 grit to apex, then change to 200, then 400, etc. Are you betting that that would give me flat, 15° contact between these different stones and fix the problem?

    #48317

    Drew
    Participant
    • Topics: 11
    • Replies: 72

    Here’s the last experiment I’m doing today to highlight the problem:

     

    100 grit, ground fresh bevel flat, apex to back of bevel, bur raised on both sides. Clockwork, and all  is well. My reasoning suggests, strongly, that if the 100 grit can reach all parts of the bevel flat, regardless of how the knife is, then twisting the paddles from 100 to 200 on the rod, cubing to 15°, the 200 grit should mimic the contact of the 100s. It should be a carbon copy of the courser grit.

    Fingers crossed I can post these pictures.

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    #48322

    MarcH
    Moderator
    • Topics: 58
    • Replies: 1855

    In the photos you posted, your remaining marker on the bevels indicates your not reaching the apex always.  That picture clearly illustrates the clamping lean you see.

    The way it is now you’re not sure it is repeatable.  If you remove the knife, the LAA and the material between the knife and jaws.  The next time it may not come together the same way.  A zero reference, vertical knife, is the standard starting position for predictable repeated results.  For known, consistent and predictable, blade leans due to a clamping offset, with an angle measurement of the lean and mathematical calculation you can yield a correction factor to adjust your individual side guide rods settings to even out you results.   Divide the lean angle amount by two.  Add the 1/2 it to the right side angle setting and subtract the 1/2 from the left side setting.

     

     

    Marc
    (MarcH's Rack-It)

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    #48323

    Drew
    Participant
    • Topics: 11
    • Replies: 72

    200 grit, 15°, marker to illustrate

     

     

    That dog won’t hunt.

    Attachments:
    #48328

    MarcH
    Moderator
    • Topics: 58
    • Replies: 1855

    Here’s the last experiment I’m doing today to highlight the problem: 100 grit, ground fresh bevel flat, apex to back of bevel, bur raised on both sides. Clockwork, and all is well. My reasoning suggests, strongly, that if the 100 grit can reach all parts of the bevel flat, regardless of how the knife is, then twisting the paddles from 100 to 200 on the rod, cubing to 15°, the 200 grit should mimic the contact of the 100s. It should be a carbon copy of the courser grit. Fingers crossed I can post these pictures.

    So far so good!  Are these last pictures 100 grit?

    Marc
    (MarcH's Rack-It)

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    #48329

    MarcH
    Moderator
    • Topics: 58
    • Replies: 1855

    Question: did you hold the stone(s), each and every one, flat against the square and inspect for flatness or dishing?

    Marc
    (MarcH's Rack-It)

    1 user thanked author for this post.
    #48330

    Drew
    Participant
    • Topics: 11
    • Replies: 72

    Man… Listen. Either I’m not getting a fairly simple concept, or you aren’t. I’m about to lose the last of my mind.

    All I want is for the finer grit stones to contact the bevel the same at the created, ground degree as the courser.

    All things being fixed and constant, including the tilt of the blade, bevel stone contact should be constant between grits as well. The only thing variable are the paddles.

    Now, to get an even bevel on a tilting blade, I’ll hold on to your formula for when I run into that problem in the future. Thank you for that.

     

    #48331

    MarcH
    Moderator
    • Topics: 58
    • Replies: 1855

    Does the remaining marker, down low, show 200 grit isn’t scratching everywhere from apex to shoulder?

    Marc
    (MarcH's Rack-It)

    #48332

    MarcH
    Moderator
    • Topics: 58
    • Replies: 1855

    You finally stated in clear and concise words what I asked you in the long involved post last night.  I never stated you were doing some wrong or your observations were wrong.  I was just asking you, trying to understand where in the grit progression you saw the difference(s).   That it’s only the fine grit;1000 grit!   If it’s only the last, 1000 grit that you see behaves differently, then your only choice is to try something different!  You inspected it and didn’t see a problem you could fix.  Your only option is to replace it.  Try a different 800/1000.

    Maybe the finer grit stones are worn more than the coarser stones so they don’t behave the same.

    Marc
    (MarcH's Rack-It)

    #48340

    Drew
    Participant
    • Topics: 11
    • Replies: 72

    I’m done, Marc. It’s many of the stones, 50-1k. Thank you for your effort. Good stuff.

     

    I’m going to request another set of stones, or return the whole thing for a refund.

    #48341

    Drew
    Participant
    • Topics: 11
    • Replies: 72

    Oh man, our replies were overstepping each other. I missed a few. The 200 grit left the marker, and I haven’t checked for dishing, yet. There’s a good straight-edge on the property, I’ll have to track it down.

    It feels like my eyes will start weeping blood like a WE stigmata if I pursue this further, today.

     

    God bless you all, and I’ll get to replying proper after I go calm down.

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