grinding help please

[Tune_up]

I finally got my 2x72 grinder up and running and am working or the learning curve. I ground a couple out of mild steel for practice then jumped in, completely ruined the third attempt, got into trouble and the more I tied to fix it the worse it got, finally got the edge too thin and overheated the tip. I saved the blank and when I get better I may try to "re-design" it.
My question is about the plunge and where it meets the bevel. The left side of my blanks make a nice curve, the right goes above the bevel line and I can't figure out what I am doing to cause it. I will make several passes and everything looks good the next pass and its there. If its early and my grind line is still low I have managed to fix it but in the blank I trashed I got into the spine.
I marked the lines with a marker since I couldn't make it show up well in the pic's.
Thanks in advance for any helpfull suggestions you can offer.

 

[rhinoknives]

From what I can see?
It's called being right handed. :biggrin: It looks like your pressure and angle are off and you are rolling into the spine when holding with your left hand. You also seem to have some 2" grind problems happening?

Dust yourself off and start again and work with your left or weak side first and then match your grind with your right or dominant hand.

Every maker has a box of Turkeys! Anyone that say's they don't? Has some real issues to deal with.

I found that by grinding already Heat Treated profiles I get crisper grinds with less problems and do about 85% of my grinding after Heat Treatment. Also slow your machine down if it's variable or step pulley setup and use fresh sharp belts.

I hope this helps?

Laurence

www.rhinoknives.com

 

[BarryC]

Laurence gave good advise. To add to that the contour on the edges of your platten and the amount your belt hangs over the side of it matters when you are trying to match up the curve at the top of the plunge. If the edges are not the same you will have a much harder time making the curve be the same size. Same thing is true if you hang more belt off one side that the other. Practice, practice, and practice. The only other advise I can give is don't attach the platten with the blade when starting the grind. Lightly touch the edge to the platten not enough to cut then roll the blade down so that the flat is flatly against the platten with no pressue so you are not cutting yet. From here you are starting with the blade flat against the platten, then even pressure across the width of the platten and even speed pull the blade across. I have seen it both ways but I prefer to stop and pull the blade away from the belt before the tip makes it half the width of the belt.

Oh and by the way did I mention you need to practice? Don't just go at it. It is all about feel and sound. You can hear when you are not flat against the platten. Practice with a purpose like getting the feel for grinding, then figuring out how putting pressure somewhere on the blade changes the grind.

 

[DonL]

That knife looks a lot like mine! As Laurence said, it's caused by uneven pressure and angle. I've made about 40 knives and even now, this will happen if If I don't pay attention to the pressure I'm putting on the blade with my weak side. I start off with my left hand then switch to my right hand. I do this in hopes of matching what the left side looks like because I have more control with my right. (my strong side)

One of the things I found was that I was not holding the blade at the same angle. I'd also move the blade ever so slight upward with my strong hand, causing a nice curve at the plunge. On my weak side, I was dropping my hand just a little. Also when using my weak hand, I caught myself trying to put pressure on the blade with my right hand (the one guiding the blade across the belt) instead of using my left (weak side) hand (the one holding the handle and one that should be controlling pressure).

Another thing I caught myself doing is whenever I'd put the blade to the belt, on my weak side I was starting at the plunge and sweeping to my left. The plunge area would contact the belt first and I'd rotate the blade slightly so the rest of the blade met the belt. This cause divots near the plunge. I've since started either at the end and pull toward the plunge or start in the middle. I'm also more aware of this and try to ensure that the whole blade meets the belt at one time.

Do not throw away any of your mess ups. I hang mine on a peg board. Recently, I was able to "rescue" 6 knives I'd messed up on when I first started out. I had gained enough experience and knowledge to fix the grinds on them. Now I have a few more that are still hanging because I'm not real sure how to fix them, but eventually I will!

I don't think most people pick up flat grinding easily. It has (and still is) taking me a long time to get somewhat consistent results. The learning curve can be a real PITA, but keep at it. Try to make your next knife better than your last. Don't get upset when you mess up one knife, it's going to happen and you need to accept that and move on. Just cut out another and start on it (this is another excellent reason to use Aldo's 1084. It's cheap and makes a great knife). Eventually you'll be able to go back and save some of the early ones. Some people will suggest a jig, and I did try one for a few knives. But I wanted to learn to freehand for the greater freedom it allows. While frustrating many times, looking back I'm glad I made the decision to learn to flat grind freehand.

 

[EdCaffreyMS]

It's called being right handed. It looks like your pressure and angle are off and you are rolling into the spine when holding with your left hand. You also seem to have some 2" grind problems happening?

Dust yourself off and start again and work with your left or weak side first and then match your grind with your right or dominant hand.

AMEN! AMEN! AMEN! It could not have been said any better then that!