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Deciding on Bevel angle?

Discussion in 'Shop Talk - BladeSmith Questions and Answers' started by Randydb, Mar 25, 2019.

  1. Randydb

    Randydb Basic Member Basic Member

    661
    Sep 27, 2014
    I have ground 2 sets of bevels with the bubble jig. Same profile of knife, but one is ground using 10, 5 then finally 4 degree angle on the bevels and the second one I have only ground to 5 degrees.

    In another thread someone said it was personal preference where I stopped. But is there advantages to one over the other? A bit more material removed on the 4 degree bevel so knife is a bit lighter?

    Any other reasons to go to a 4 percent angle on the bevels?

    Also, I ground these using 60 grit first. When I go to 120, 220, 400 about how many passes should I be making at these grits? 3-5....until I get rid of the scratches from the previous grit? IMG_1435.jpg IMG_1434.jpg
     
    Branson1369 likes this.
  2. Hengelo_77

    Hengelo_77 Basic Member Basic Member

    Mar 2, 2006
    Your top knife will be stronger, the bottom one will slice better
     
  3. Stacy E. Apelt - Bladesmith

    Stacy E. Apelt - Bladesmith ilmarinen - MODERATOR Moderator Knifemaker / Craftsman / Service Provider

    Aug 20, 2004
    The lower the main bevel angle the thinner the blade near the edge. Slicers are generally thinner, heavy users and camp knives thicker. 4° or 5° are both good.
     
  4. Busto

    Busto KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Jul 26, 2011
    Bingo!!! Your eyes are your tool of choice here. There is no set number of passes per grit size...Depending on the final finish choice the better the starting finish the better and easier the final finish will be to achieve. If you leave any 120 grit scratches they will come back to haunt you.
     
  5. KNelson

    KNelson

    99
    Jan 9, 2019
    As stated above but more clearly IMO, the more acute your angles are the more slicy. The height of the bevel may not always have to do with the slicyness as the same angel will change height with different thicknesses of the stock your working. Try a bunch of different angles and see which one cuts good for the task you want that is also strong enough, keeping in mind the thicker the spine will reduce the cutting performance as well.
     
    Fred.Rowe likes this.
  6. Fred.Rowe

    Fred.Rowe Dealer / Materials Provider Dealer / Materials Provider

    May 2, 2004
    Good Morning,
    To help you learn about which angles produce what type of bevels; start with a 5 degree angle when grinding the edge to heat treat thickness, instead of the ten degree angle. You will find many knives can be ground using this one angle [five 5] degrees.
    When someone with a lot of experience told me, when I ask him about sharp; "it's what is behind the edge that counts. How much resistance to slicing is there when you cut a tomato. If the portion of the bevel directly behind the cutting edge is thick, the knife will not slice well, if the steel right behind the edge is thin, the knife will slice well. There is no real edge. The edge of a knife is where the bevels meet each other. So to say an edge is sharp is really saying, the steel "behind" the edge is thin and the angle of the two bevels is acute. If you ponder this a while, it will make sense. If you have a set of micrometers, measure the thickness behind the edge when you have the bevels ground. Remember, there is no "edge" on a knife, it's the steel behind it that is critical.
    When choosing how thick a steel should be, to produce a knife that cuts in a certain manner you want to be thinking about, "how thick is the steel behind the edge" after the bevels are ground. This will help you decide what thickness of steel should be used to produce a specific knife that cuts in a specific manner. Or, don't expect a knife ground from 1/4 inch stock to cut in the manner of a blade, ground from 1/8 inch stock.
    Grinding bevels and sharpening to produce a cutting edge, are two completely separate functions.

    Regards, Fred
     
    Natlek likes this.
  7. Randydb

    Randydb Basic Member Basic Member

    661
    Sep 27, 2014
    I make native american flutes too. Often the answer to questions is, "It depends on what sound you want. But either way you won't lose" I think the answers here are similar.
    I will be doing fine with either angled bevel but I can focus in on certain qualities that will be advantages in certain situations. These blades are just 1/8 and less than 1.5 inches tall. I have profiled 8 blades total. 3 pairs of blades and then two others that don't have partners(hope that makes sense). So I think each pair I will do one 5 degrees and one 4 degrees. See what differences there are when I make knives out of them.

    I found that I was much better at holding the second blade stable as I ground bevels. Everything is a lot flatter. Also could push a lot harder on the grinder. But I burned my fingers a few times. Geez the heat gets going fast. At first I was too stupid to put my fingers in the water bucket. Now the blade and my hand goes in the water if things are burning.

    Should I be wearing a tight fitting glove as I grind? Do I damage the blade if I heat it up too much? I know after heat treat I don't want to heat it too much. But now?
     
    Fred.Rowe likes this.
  8. john april

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

    Feb 27, 2006
    do you have any dykem machinists marking fluid ? if not, color your whole blade with a sharpie permanent black marker between each grit. i used that to teach myself not to miss any spots, and when i had gotten all of the previous scratches out.
     
  9. john april

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

    Feb 27, 2006
    yes you will damage the heat treat if it gets too hot. dip in water on every pass. that should keep you safe. also the finer the grit, the more friction and heat build up. the higher in grit i go, the slower i run the grinder. if your grinder is not variable speed, press lighter on the belt as you go up in grits. i grind with gloves, ( the first time you lose the tip of a knuckle on a 36 grit belt, gloves might seem like a good idea although most people consider them a hazard) i wear unlined goatskin gloves, fairly snug fitting. i wear out spots on the fingers, and keep adding layers of masking tape as it wears through.
     
  10. Randydb

    Randydb Basic Member Basic Member

    661
    Sep 27, 2014
    Geez...I could have thought of that! I don't have dye, but I have lots of big sharpies.

    I have a VFD so I will slow down the grinder. It was on the finer grits that I was burning my fingers fast. Slowing down the grinder didn't occur to me either.
    I saw in other threads that gloves could be dangerous. I have a set of tight fitting leather riding gloves I may try down the line. I've take off skin on my 6x42 belt sander on other projects so I know I don't like it, but I can handle it too.

    Thanks for everyone's help here.
     
  11. E.Carlson

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

    660
    Mar 28, 2016
  12. Randydb

    Randydb Basic Member Basic Member

    661
    Sep 27, 2014
    I just slowed my grinder down to 35hz, sharpied a blade that I had ground with 60 grit and then went over it with 120 grit. 4 passes and the sharpie was gone. Crap. I waaaaay over did it with the first blade. Maybe 15 passes with each grit at 60hz on the first blade. I deserve the blister on my finger. I'm enjoying some parts of the learning curve more than others!
     
  13. Fred.Rowe

    Fred.Rowe Dealer / Materials Provider Dealer / Materials Provider

    May 2, 2004
    Somehow I missed your post before putting my post up. We addressed the same issues so what I wrote was a bit redundant. Fred
     

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