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How to fix this grind?

Discussion in 'Shop Talk - BladeSmith Questions and Answers' started by JSCutlery92, Feb 16, 2019.

  1. JSCutlery92

    JSCutlery92

    9
    Feb 13, 2019
    So, I have a question about how to fix a grind that I'm doing, that varies a bit on both sides. A little extra info: I'm a new knifemaker without much experience, I'm working on a 4x36 harbor freight belt grinder with ceramic belts that I got from Trugrit. My work rest I had to modify a bit because it wasn't quite big enough/didn't clear portions of the beltgrinder that I can't change, and so I kept hitting lips and edges, so my workrest is pieces of plywood screwed together. I also just started using a new bevel jig that I made today on this knife as well.

    As you can see in the pictures (Ignore the sleeping cat, I took the pictures in my bedroom) one side of my knife has a very interesting curving bevel line. Admittedly that wasn't my intention, but it actually turned out kind of unique looking. The other side, has a straighter line, that dips up a bit near the edge of the blade.

    At this point I figure that I can't really make the straight side, into a curving line like the other side, so I'm looking to just straighten out the curving side a bit. That being said, I'm not entirely sure how to do it, I'm also not sure how I wound up with the bevel line curving like it did. I applied even pressure throughout my grind, and I didn't change the angle of the blade against the belt at all. I did the same method and angles, as well as pressure, for both sides and wound up with two different grinds.

    I've tried working on the curved side and adding a little extra pressure on the portion of the line that curves down into the bevel, but it doesn't seem to do anything. So what would be the best way to fix this? And how can I avoid something like this in the future? Since I thought that I used the same pressure and angles on both sides, I shouldn't have gotten two different lines, so any advice for my future grinds to try and stop this from happening again? WIN_20190216_20_49_15_Pro.jpg WIN_20190216_20_49_29_Pro.jpg
     
  2. tinkerer

    tinkerer

    368
    Oct 6, 2009
    My advice, step away from the belt sander and go to a rough stone and/or file and work in smooth, even strokes to even out the grind. I like belts for hogging, but hate them for detail work. For your comfort, I have a blade I'm working on now that needs a little coersion to reach a "perfect" grind.

    Larry
    Tinkerer
     
  3. TILLER

    TILLER KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    131
    Jan 1, 2011
    In my experience it could be a couple things. First things first I like to grind the flats flat first. If the bar stock is not pretty flat, it makes it harder to keep it even. Same with it being pretty straight. If it’s bent it will be harder. I hold the knife vertically along the platen. You may or may not have the space on your grinder for that. Check it on a flat surface or maybe some calipers.

    You may just be letting up on the pressure as you move along the grind line. It’s easy to put more pressure as you put the blade up to the platen.

    Search the forum for something like 2” line (I forget what it’s commonly called).

    Try a new belt. Sometimes it is shocking how much better a fresh belt cuts and helps keep things even.

    Check that the platen is square and flat to the belt.

    Good luck keep after it. Grinding takes practice.
     
  4. JSCutlery92

    JSCutlery92

    9
    Feb 13, 2019
    Larry, I want to thank you for your reply, the belt grinders are absolutely great for hogging away at material, but they definitely lack in the fine details department. At least the larger (And cheaper) 4 inch grinders do! I do have a couple files, so I can set up a little file jig and try that out to see about getting some even lines in there, that's definitely a good idea and something worth trying, so thank you!

    Tiller, I checked the flatness of the stock after I finished shaping it, but before I started grinding and everything seemed pretty squared off. Nice flat lines all the way around, and flat surface area's on the front and back. At least it certainly seemed that way when put to platen and other flat surfaces. I might definitely be letting up on pressure a bit, although I tried not to. When I put the steel to the belt at the start of the grind, I I've been pushing a little harder and holding it in place for a second before I start moving so that I can set the plunge line a little better at the start of the grind. Once I start moving it away I might have it in my head that I don't need as much pressure anymore, so I lighten up without realizing it.

    I'll check the forums for the 2" line, I'm always trying to learn more especially since I'm new to the craft. And I'll try a new belt as well before I get into trying a file. I'm trying to get the most out of each belt as I can so I'm not spending to much money on them and wasting belts, but that may be what's messing up some of my grinds. I'm fairly new the using machines like this, so I'm still trying to get a feel of what a worn out belt feels/looks like, and one that still has some life to it.

    I also checked the platen and how the belt lines up to it, and everything is perfectly square, flat, and even. I had wondered if maybe the platen itself was a little off, or warped in some way, but its fine all along the length of it.
     
  5. E.Carlson

    E.Carlson KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    801
    Mar 28, 2016
    Practice and practice some more. Getting those crispy grind lines is one of the most difficult parts of knife making for me. It has caused me to stick to doing full flat grinds to avoid my weaknesses, but I have vowed to take it on this year.
    From your pictures, it looks like you mainly need to focus on stable pressure. Since you are stuck with a single speed, I would use a higher grit belt and go slowly, so when you see your lines getting squirrely, you can adjust to correct them before too much material is removed.
     
  6. john april

    john april KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Feb 27, 2006
    looks like one or more of these: uneven speed of pull across the platen, uneven tip toward the belt on the work rest, or uneven pressure against the belt. in my early days of grinding i would fix that with a hand file before moving onto the next grit. because lots of times when i was trying to "fix" something i would make something else worse, then have to fix that, then go back to the other side and try to make that match my fixed screwup lol :rolleyes:
     
    mknife likes this.
  7. JSCutlery92

    JSCutlery92

    9
    Feb 13, 2019
    [​IMG] I took a bit of everyones advice and attempted to fix my weird grinds today. After a bit of playing with everything, it all seemed to work out quite well! I had wanted to etch this knife, so once I worked out the grind lines, I sanded it all down and put it through a few etching cycles, and this is the end result. I just want to thank all of you for your help and advice! Now I just need to figure out how to fix the slight botching of the etch lines, since some of my nail polish didn't hold like I had hoped....
     
    Kali4nia and E.Carlson like this.
  8. Kali4nia

    Kali4nia

    175
    Aug 12, 2015
    In my humble opinion. Your steel isn't flat. You can't grind a straight line on a curved surface ( easily ). It made a world of difference for me. Also doesn't look like you've removed too much metal. When I started I would hog with the grinder then finish with files and sandpaper as previously suggested to prevent ruining yet another blade.
     
  9. Kali4nia

    Kali4nia

    175
    Aug 12, 2015
    ** sorry, didn't see you fixed it. Good job
     

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