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Top bevel line wavy


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This is my first blade.  I am having an issue and want to find out if I am doing something wrong, or if my setup is the issue.  Through the university of Google, I have seen on multiple videos that when you start beveling with a jig the bevel line is straight and crisp.  Mine, as you can see in the picture below is wavy.  I am being as consistent as I can and the travel of the jig appears to be smooth.  Its a home made jig on a Harbor Freight 30 x 1 belt grinder.

 

IMG-20210130-WA0002.jpeg

 

20210131_111026.jpg

 

What causes this?  Is it the platen is not rigid enough and deflects?  Could it be my jig?  Could it be the table?  I have checked that all are true to each other, but it is static when I measure.  When the belt is moving can it all change?

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Most likely a combination of the platen not being solid enough and the narrow belt.  Somehow the angle is changing.  Another problem seen sometimes is "belt bump."  This is when the joint of the belt is a little thicker than the rest of it, which causes a distinct bump that can shift the blade.  Narrow belts make the issue worse, since a narrow belt can bite deeper than a wide one.  I know, you don't have the option of a wider belt at the moment, but even with a two inch belt when using a jig you can sometimes see a little line every two inches down the length of a blade.  

 

That's why I freehand it.  A jig is great IF the entire setup is rock solid.  Any play or vibration anywhere in the system will be telegraphed into the steel.  When you freehand grind, your body absorbs the little variations and only a BIG bump will throw you off. 

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It also seems that maybe your angle is a bit too much.  Ideally you want the angle to such that when your edge thickness is where you want it (dime size for reference) the bevel will be at the height that you want it.  It seems your edge is still a bit thick.  If you stick with the angle that you have your jig at, and keep working the bevel, it will take the edge thickness down at the same time, it will bring your grind line higher.  I don't use a jig, but with freehand grinding, as the edge thins and the grind moves towards the spine, the top bevel line may straighten out a bit as you go along.  From the top pic, it does look like to are getting that 1" bump line on the bevel.  That is from going into the belt at an angle (the handle close to you and the tip closer to the belt.  Work on approaching the belt dead flat and that should help.  Just my $.02, but keep at it, practice, practice, practice. 

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A lot of good advice above.  One other thing to consider would be to have two leveling screws on your jig instead of just one.  You could be inadvertently rocking a little bit during your grind.  Having a second point of contact along that back edge may help to alleviate that.

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I do most or all of my pre heat treat with jig.

Even with a jig I am constantly adjusting....the grind never just falls into place.

Post heat treat most if not all of my grinding is freehand.

Not sure if this will make sense.....but freehand you arent restricted to being 90* with the belt.

You blade is short enough its not gonna be super helpful....but being able to hold the blade 45* both directions helps me to get a more uniform grind.

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