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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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  • #48227

    Drew
    Participant
    • Topics: 11
    • Replies: 72

    (Deleted my previous, double-text post. Trying this again:)

    Out of the shadows with another mystery…

    I’m making my first knife via stock removal. Found an old, rusted file in the lava, hacksawed to shape, and ground a Scandinavian bevel with the 50 grit. Labor of love. Rediculously hard steel, but no way to anneal.

    Decided to do this one perfect. Complete scratch removal, alternating scratch patterns, flawless apex, the works.

    Noticed that with each grit change, the stone would only contact a part of the bevel. Real slight difference in contact. Not too big a problem to grind it flat to apex. Multiple readings of cube, .05 degree adjustments to get it solid on 15dps.

    Now I’m on 1k…. Getting difficult to grind it flat to 15. What’s going on? I asked the fellas at WE if I need to lap the stones, and they said the equivalent of, “For the love of God, no. It’ll mess them up.”

    So, if I’m grinding perfect flat each grit, changing grit, cubing straight on 15°, holding the stone the same, pressing the knife in the same spots to stabilize…. Where am I going wrong? Is this something you all have to deal with? Just a hazard of doing ginormous bevels? Even without Clay using a cube between grits in the early videos, just using the degree bar, I don’t remember seeing this problem for him.

    It occurs to me that the scratches I was getting on my convex attempts may very well have been this issue.

    PS, I could just dial forward or back till it contacts full on, but I’d really like to get the degree set for each grit the same. And I still don’t know what will happen when I get to the lapping film. I can’t imagine grinding a slightly new bevel will be an option like the stones.

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    #48234

    Organic
    Participant
    • Topics: 17
    • Replies: 853

    I think what you’re experiencing is a symptom of the small bit of play in the system. The angle can vary a little bit based on where you grip the stones as a result of the rods and stones not being a 100% perfect fit. I have not personally measured it, but I have seen others say it can be as much as a 0.3 degree per side difference between holding the stones at the top or bottom of the paddle. Since you are grinding very wide bevels, minute angle differences will be much easier to see than under most circumstances. The way to compensate for this is to be as consistent as you can with your technique and how you hold the paddles. I like to hold them at the bottom for safety and consistency.

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    #48235

    MarcH
    Moderator
    • Topics: 58
    • Replies: 1857

    Drew looking at the photos your bevels definitely appear faceted.  Indicating they’re applied at different angles.  I don’t know if the knife is slipping in the low angle adapter, I see you’re using. Or possibly the low angle adapter is slipping or shifting in the vice jaws.  Possible your guide rod angles are not staying locked and these are slipping allowing the set 15 dps angle to wander. But definitely something is off. Possibly something else is loose; square angle bar or bracket ends.

    The only thing I can suggest is to check the knife for secure clamping, and everything else that may be loose.  I cannot see in the pictures which W. E. Model setup your using.

    In the pictures it appears that each side bevel is different.  They are both not reaching the apex.  Is the file knife clamped vertically and centered, or possibly it’s leaning?  Is the file bent, warped or twisted?  The file knife is very rusted possible this is effecting how it’s seated in the LAA.

     

    Marc
    (MarcH's Rack-It)

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    #48236

    Drew
    Participant
    • Topics: 11
    • Replies: 72

    Unfortunately, I’ve adopted the habit of always holding at the bottom, and never letting my finger-top from going above the apex. This was after your all’s suggestion to do so a few weeks back. It’s consistent.

     

    So, barring slop in the stones and rods, what else could it be? When consistent with form, clamp nice and tight with no play in the blade, using the original angle cube, and using stones with 20 blades worth of break-in, have you guys ever experienced this?

    #48237

    Drew
    Participant
    • Topics: 11
    • Replies: 72

    I’ll go through the screws, tightening them.  It’s weird: I can scrub, then check the cube, and it’s right on 15, or just off by .05. I’m not seeing evidence of play.

     

    I’ll check to tighten everything I can. My thought is, if it’s clamped and secured, not moving, could there be something up with the cube, or the wear in each grit of stone? If it’s not movement in the blade or rods, there must be a silly-simple solution regarding stone thickness and angle, or something along those lines.

     

    Ok. I’ll start changing variables to see what influences the scratch pattern. Screws, clamp, LAA, thumbscrews.

    #48238

    Drew
    Participant
    • Topics: 11
    • Replies: 72

    PS, not sure if helpful before I check everything: I can use the 600, right is low, left is high. Scrub to a reading if 15° flat from apex to back of bevel. Take an end reading of 15° solid. Wipe and switch to 800, cube to 15°, scrub, and the problem is reversed: right is high, left is low.

    #48239

    MarcH
    Moderator
    • Topics: 58
    • Replies: 1857

    You stated you’ve done 20 knives.  If those sharpened to your satisfaction, the only difference is this particular knife.  It doesn’t have to shift much to show the errors you’re seeing.

    Marc
    (MarcH's Rack-It)

    1 user thanked author for this post.
    #48240

    Drew
    Participant
    • Topics: 11
    • Replies: 72

    I’ve actually done a post on convex scratching that looks to have been this issue. I changed my stone holding grip, and the issue of scratches remains.

     

    The knife isn’t moving, the cube registers nothing unusual.

     

    Here’s an experiment I just did: I blacked the bevel, cubed the 1k to 15°, removed the marker which showed the part of the bevel not hit. Rotated the paddle to 800, cubed to 15, and removed the marker left by 1k.

     

    Then I rotated the paddle and did it again. Same results with each grit.

    Attachments:
    #48245

    Drew
    Participant
    • Topics: 11
    • Replies: 72

    Second rotation:

    Attachments:
    #48248

    MarcH
    Moderator
    • Topics: 58
    • Replies: 1857

    Drew in the photo KIMG3771.jpg it appears as though the LAA is clamped angled to the left in vice jaws.  Is that effecting the knife bevel moving it off center to the left?

    Marc
    (MarcH's Rack-It)

    #48249

    Drew
    Participant
    • Topics: 11
    • Replies: 72

    I’m not noticing any play, and the hex screws are tight tight, as is the lever for the cam. Angle cube isn’t registering any weirdness.

     

    This is the position it’s been in since the 50 grit. I haven’t removed it since the start of the project.

     

    Here’s another experiment: same as before, but with both paddles. First pics are the 800, 15°, second pair is 1k, 15°. Rotated on the rods, not flipped.

    Attachments:
    #48254

    Drew
    Participant
    • Topics: 11
    • Replies: 72

    Listen, I do appreciate the feedback and troubleshooting.

     

    This has been a uniquely bad day, and it’s probably showing itself through my text.

     

    I will probably bring this up to WE customer service. I can’t seem to tighten anything else without these changes in angle happening between grits.

     

    Thank you all for your suggestions. Keep them coming, it was brainstorming that resulted in your suggestions to hold the paddles at the bottom for consistency. There’s good info coming up.

    #48255

    MarcH
    Moderator
    • Topics: 58
    • Replies: 1857

    Drew, please be patient with me and this trouble some situation…

    The posted image KIMG3779  with the knife pointed to the left, the bevel is at the top and the marker is at the bottom of that bevel, correct.

    The next image KIMG3780  the knife point is facing right and the bevel is scratched on the bottom with the marker on the top of that bevel, correct.

    When both side angle settings with the stones are verified at 15º with the digital angle cube, the only way to get those marker/bevel results is with a knife that’s leaning to the left.

    The LAA is a screw type clamp by the nature of the clamp (i.e., one side fixed and the other side moving) it can lean the blade towards the fixed side.  Also the vice clamps that LAA on that fixed side of the LAA.  If the knife is leaning even very slightly and the vice holds the LAA off center simply due to the design of the LAA it could be just enough to show those differences.

    If you place a straight edge directly against the left side of the vice base, hold it 90.0º vertical and measure the distance between the vertical straight edge to the clamped knife edge.  Then repeat the test with the straight edge held 90.0 º vertical and in direct contact with the vice at the base now on the right side.  I believe you’ll measure the right side knife edge is further than the distance on the left side.

     

    Marc
    (MarcH's Rack-It)

    #48256

    Drew
    Participant
    • Topics: 11
    • Replies: 72

    My brain hurts, but I’ll try. Tell me if this is correct figuring:

    If the blade’s locked in, but off center by 2 degrees, that’d just make an assymetrical grind. 13° one side, 17° the other. This’s been ground from raw stock at 15° per side. As long as it doesn’t jiggle, you’d have a 13/17 split, with similar contact between all flat stones.

    This repeatable angle change between not only 800 and 1k, but 800/1k on each side makes me think that everything is locked down and consistent. I don’t see how, but maybe I dished out these stones in those few months?

    #48257

    Drew
    Participant
    • Topics: 11
    • Replies: 72

    I’m real sorry if I’m just not seeing something simple, right in front of me. Like trying to tell a driver the car won’t go cause the parking brake’s on, and them not getting it.

     

    I’m going to take a break from this, and reread the posts with a rested, fed, and watered brain.

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