Bevel grinding advice needed

R

Rasmusiii

Member
Hello!

Can anybody please try to explain what I'm doing wrong here.
Sees like this always is the start of my grinding - the rest
is just trying to correct my error. Obviosly I'm trying to to make a
straight line but this seem almost impossible.
Couple of drawings here - hope they explain what's going on.

grind1.jpg


grind2.jpg


Regards
Rasmus
 
Watch where the sparks are coming off the belt when you grind. Your problem is from the blade/bevel making harder contact at the edge of the platen or wheel, you need to move that hard contact patch from the edge towards the center. Basically you need to pull the end of the tang towards you a tiny bit, but the amount is so small that it is more a change of pressure that a movement.
Also watch out for belts that are worn unevenly, dull grit at the center and sharp grit at the edge will cause it to dig deeper at the plunge.
 
I assume from the drawing that you are using a jig? If the drawing are "true to life" the first thing I see is that your work rest is too low....if it's a hollow grind, with a jig your seeking, the radius of the contact wheel need to engage the blade more towards the spine. The other issue I see from the top drawing is you were "heavy handed" with your right hand, OR you where trying to grind in both directions, and the area of the plunge is were you changed directions.

I will tell you, I am against using jigs to grind a blade, in all but very specific situations. They are far too limiting.
The best thing you can do is seek out someone who can give you a little training, or if that isn't possible, it's going to take time and practice. When I first started grinding, I kept a 5 gallon bucket next to the grinder.....about once ever two weeks I would haul off a bucket full of wrecked blades to the scrap yard. Even after 25+ years of doing this, it's not uncommon for me to mess up grinding a blade...it's just that now I have enough experience to know/understand how to fix it.
 
I'll second what Ed said. Free hand grinding allows one to 'feel' what's going on in a sense. Grinding a blade flat and even has a lot to do with pressure and slight torque or twist. That's really hard to do with a jig, if not impossible. Free hand also lets you grind a nice even pass as you get into the belly of blade because you can drop the butt of the knife and slightly pull the tang out as you get into the tip area.

From your first drawing, if you have a spot where the grind is farther towards the spine of the knife (that is to say a higher grind) in one spot, that could mean that you used more pressure into the belt in that area. Then you have to grind more on either side of the high spot and less or use less pressure in the direct area of the high spot. This will blend your grind so that it is all the same heigth.

I hope that didn't confuse you more.
 
If you're using a jig, the edge might look like it gets thicker and thinner. Scribe a set of parallel lines on the edge and grind evenly to them, the rest of the grind on the blade should follow where it may and be ok. But...the folks north of this note are giving you great grinding advise.

Good luck with the practice, Craig
 
Thanks alot for good advices.
I think that uneven worn belt can be part of my problem, Justin.

grind5.jpg


grind4.jpg


grind3.jpg


Guess my drawings aren't that telling the hole story so I'm adding
a few more images.
I am using a jig, and without it I would be like a skater on the ice for the first time. I will take your advice, Ed and try to get someone to try to teach me. In the meantime I'm gonna try out all your suggestions.
Thanks J and Craig.

regards
Rasmus

www.rasmus3.com
 
Looking at the middle photo, I think confirms what I said previously.....you need to flatten the angle on the work rest a bit, and raise it a bit. This might be hard to envision, but you want the highest point of the radius on the contact wheel to end up at the bottom of the hollow your trying to create. That's the biggest problem with jigs and rests..it often takes more more time to get the rest and jig correctly positioned, than it does to do the actual grinding......then once you get everything set for a specific style/shape/type of blade, you must go through the whole thing again if you change style, shape, type or size of the blade. Once you understand the basics of freehand grinding, they apply to ANY blade size, style, type, or shape of blade that you can imagine. It takes time and effort to learn/understand, but it makes you versatile and confident in what you can do.
 
Just wondering, does your work rest deflect a little particularly out on the right side. Not picking on your equipment at all. The jigged hollow grinds that I've seen are usually ruler straight. Just wondering if that might be part of that slight wave in the grind line before it gets to the clip. Also, you might loose a little consistency if you need to move the work rest to change a belt. Thanks for the pictures, and I thought you did a great job with the drawings.

Sorry if I'm seeing it wrong, Craig

Just can't help myself, if belt tension is holding the grinding wheel on, it might not be a bad idea to put some type of retainer over the open axle fork. Belts let go every now and then. Again, I apologize if I'm not seeing something right.
 
I'm not being offended by anything you've said - I understand that you are just trying to help me and are very grateful for that. I'm trying to coordinate all the information you have given me and hopefully it will improve my results. I'll try raising the work rest. As it is now I really have to move the work rest to change belts, so I will look into that.
Thanks for the overwhelming response.

Rasmus
 
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