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Thread: Bevel grinding, what am I doing wrong?

  1. #1

    Bevel grinding, what am I doing wrong?

    I started work on my third knife today. I was trying for a half-height flat grind. On all of my previous knives I have tried for a flat grind, or a scandi grind first. These never seem to come out even. I wind up going with a full height convex grind because it covers the mistakes pretty well.

    I've seen what I can only describe as exquisite scandi grinds accomplished on a harbor freight 1X30 sander.

    So I'd like to know specifically how to get these super even, perfect flat and scandi grinds.

    I'm using a Grizzly 2X72" grinder, and have added a ceramic glass liner to the platen.

    What grit do you start with for grinding bevels?

    Are these grinds established with a single pass on each side?

    Are they done freehand?

    What devices are used beside the bubble jig to aid in achieving even grinds?

    I want to be able to get a good grind without trashing expensive steel. I also don't have a band saw so cutting out my profiles is a time consuming process involving drilling hundreds of little holes around the profile and "connecting the dots" to cut them out. This means I've already spent the better part of an hour cutting out my profiles.



    Another question would be: If there was a single moment in your knifemaking experience where you "got it" and your bevels were way better than ever before, what moment was it? Was it a change in technique, or a new tool?

    Thanks for your hep. This forum has been a great resource so far and although I'm having a little trouble here and there I think I am way farther along than I would be without it.

  2. #2
    Join Date
    Dec 2010
    Location
    Valparaiso, IN
    Posts
    1,247
    If you're starting off with a 2x72, than you've already substantially reduced the learning curve.

    To answer your "starting grit" question, I've seen guys use anything from a 36 grit belt to a 120 grit belt. I personally start with a 60 or 80 grit and take it up to 120 or so before HT.

    As far as the grinding process itself, I freehand mine and it typically takes many many passes per side.

    To give a short explanation, I scribe two center lines in the middle and flat grind each side to the closest line. I'll start at a 45 degree bevel, grind into my center line, then tilt the blade back to about 50 degrees and grind into the scribe line again. I keep tilting the blade back until I reach my desired depth on the flat grind, or until I reach a full flat.

    How flat and straight it comes out depends a lot on practice and experience, but the best advice I can give for starting out is to keep your angles as consistent as you can during the grind, and make deliberate movements. A work rest isn't a bad idea either. Helps keeps things stable.
    -Andrew

    For the word of God is living and active and sharper than any two-edged sword.... (Hebrews 4:12)

    My YouTube Channel: www.YouTube.com/ARCustomKnives
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  3. #3
    Join Date
    Dec 2010
    Location
    Valparaiso, IN
    Posts
    1,247
    by the way, there's a thread in this forum called "flat grinding help" started by pedro G. you might look at. Lots of good advice there.
    -Andrew

    For the word of God is living and active and sharper than any two-edged sword.... (Hebrews 4:12)

    My YouTube Channel: www.YouTube.com/ARCustomKnives
    Check it out and Subscribe!

  4. #4
    Join Date
    Feb 2010
    Location
    Kildeer, IL
    Posts
    293
    I wouldn't be able to give any better advice than Andrew. I follow the advice in Richard Barney/Bob Loveless' book, "How to Make Knives. I'm still at the point where each blade is sort of trial and error. I take many passes to complete a grind. I try to start a grind at the plunge line and keep it going to the point. I usually do hollow grinds, so I'm not sure that the following will apply to flat grinds.

    If as you are making your grind you put more pressure as you get closer to the point, the grind line will follow the profile of point. In other words, curve up from the edge. You don't need to rotate the blade as you grind. Here's one I ground that way (not the insert that was my "plan").

    Remi%20'58%20almost%20finished-%20Orig%20concept%20and%20Inspiration[1].jpg

  5. #5
    Join Date
    Apr 2011
    Location
    East Coast
    Posts
    830
    I just ground knives #4-7 for preHT, so I'm with you. Whatever confidence I felt on 1-3 is on vacation. Here's what's helping me:
    - Bubble Jig, I love it!
    - Scribe lines; got a knife scribe in a GAW here, and its the bomb. I use it to scribe my lines for a half-height
    - The grind angle chart; Fred Rowe posted it up last week on one of the threads here. You look up the material thickness,
    and how wide you want the bevel, and it tells you the correct grind angle. So I set the bubble jig for that, and grind on.

    I like a convex edge myself, so I put my secondary bevels on with a slack belt (no platen) and sharpen it up.
    Semper Fidelis, Chaps

  6. #6
    Thanks for the replies so far!

    It seems I have been applying WAY too much pressure and trying to remove too much with each pass. I was thinking a grind would happen in maybe 3-5 passes per side.

    I think part of my problem is the grinder moves fast and I probably need to go to a finer grit to compensate for the excessive belt speed. I also think I need to rig some kind of system to stop the belt from riding up over the plunge line onto the ricasso. This isn't so much a problem when I gring against the platen, but when I have been changing over to a convex to fix my mistakes, I'm grinding on the slack part of the belt between the idle wheel and the top of the platen and there is really nothing to brace against to prevent this. Perhaps I'll cut out some stock and drill and tap it for screws to make a clamp for the blade.

  7. #7
    Join Date
    Feb 2010
    Location
    Kildeer, IL
    Posts
    293
    I think the less you remove with each pass the greater the opportunity to make adjustments until you are satisfied. The speed of the Grizzly is an issue but I'm sure that you'll get used to it. The blade clamp you describe is a good idea. I'm pretty sure they are commercially available in carbide. I mentioned Loveless before. He advised to use a "used" 60 grit belt for the initial 45 degree grind the Andrew describes. (Because that grind is really hard on the belts.) Then he says to use a new 60 grit belt for each blade.

  8. #8
    Join Date
    Sep 2009
    Location
    Decatur, Illinois
    Posts
    1,769
    I use a file guide to keep the plunge lines even and straight when I grind my bevels. The one I got is made of hardened A2 but I'm not sure where I got it from though I think it was probably under $40. I did see one that is made from a carbide steel that was a little on the pricy side but it would resist just about any belt. However, I don't have problems with any of my belts cutting into the file guide that I have.

    Doug
    Old age and trechery will always overcome youth and ambition.

  9. #9
    Join Date
    May 2010
    Location
    La Porte Texas
    Posts
    301
    Please don't take this the wrong way but if you don't want to trash exspensive steel don't use it. You are getting some good advise but it takes lots of practice. I know how it feels to have a picture in your head of a beautiful knife with perfectly even lines and then produceing something less. We all have experienced it. For now stay with an inexpensive steel like 1080 or 1084 once you can consistently produce grinds you are happy with then switch to a more expensive steel. The blades you make with the inexpensive steel will make good knives. Your just not out as much if you mess them up

  10. #10
    Join Date
    Apr 2011
    Location
    East Coast
    Posts
    830
    Quote Originally Posted by PetrifiedWood View Post
    I also think I need to rig some kind of system to stop the belt from riding up over the plunge line onto the ricasso. This isn't so much a problem when I gring against the platen, but when I have been changing over to a convex to fix my mistakes, I'm grinding on the slack part of the belt between the idle wheel and the top of the platen and there is really nothing to brace against to prevent this. Perhaps I'll cut out some stock and drill and tap it for screws to make a clamp for the blade.
    File guide is a good idea - forgot to mention, I use the one that comes with Fred's Bubble Jig system, and it works great! Much better than the pair of vice grips I was using before. I've also found a welder's magnet is handy - put a piece of tape on where it contacts the blade so it doesn't scratch. Gives me a better handle on the blade for a good angle.

    I only have a 2x42, and its really fast, so I can't use the orange belts for rough grit, but I have found a used Gator 60 belt works great for initial angle. Then I switch to a new 60 for the last couple passes, then 120, and 240.
    Semper Fidelis, Chaps

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