Need help on flat grind!! Plz help

G

grussingcustomknives

Joined
Oct 22, 2015
Messages
57
Ive been practicing free hand but intill i get good enough at it im using a jig. On both side there is a bump(or drop) at the end of the grind. Why is this happening and how do i fix it.
All help appreciated!!!
 
Is the Platen truly flat? Take it out and true it up on a 4 x 36 sander or have it machined flat with a surface grinder.
 
Upload your photo to Photobucket and then copy the img address and paste it in the post. Pics would help a ton. Like they say, "A picture is worth a thousand words". If its 2" from the plunge like Varga asked then its acrually called a 2" mark and is from digging the edge of the platen in when you stop at the plunge.
 
its hard to tell without a photo, but you could use a micrometer/ calipers to tell if it is a bump or dip.
 
By "end of the grind" do you mean your plunge line? Hard to tell without a picture, but it sounds like maybe you're turning your blade into the corner of the platen? IOW, you may be applying more pressure to one side of the platen, causing you to remove more material on one side of the grind. Make sure you are applying a flat, even pressure while grinding.

Don't start the pass right on the plunge line every time, but start in front of it a little bit, and work back into the plunge, THEN take it to the tip. See if that helps.

Also, make sure your belts are relatively fresh/sharp.
 
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I don't use a jig, but that's exactly how my grind looks if I apply uneven pressure or grind time at the start and end of each pass. Since you are using a jig, I'd bet time is the issue.
 
I'm calling grind time the speed that you move the piece across the belt, or the amount of time the piece is in contact with the belt in a given spot.
 
Leave the tip on the belt longer. I pull the tang away from the grinder and apply a little more pressure on the tip. It is always the thickest part. As long as every part of the blade is on the grinder the same amount of time with the same amount of pressure the grind will be straight. If one part, like your tip, does not spend as much time on the belt then the grind wont be as tall because there hasn't been as much material removed.
 
I'm looking at your first sentence and want to say that grinding free hand doesn't mean you're good.
It just means you grind free hand.
 
Matt R said:
Leave the tip on the belt longer. I pull the tang away from the grinder and apply a little more pressure on the tip. It is always the thickest part. As long as every part of the blade is on the grinder the same amount of time with the same amount of pressure the grind will be straight. If one part, like your tip, does not spend as much time on the belt then the grind wont be as tall because there hasn't been as much material removed.
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It worked!
 
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