Grind lines

Bill Thomas

Bill Thomas

Joined
Jul 7, 2013
Messages
64
I'm a newbie. I am trying to figure out why sometimes on the left side of the blade I get a straight line angled up going away from the ricasso and on the right side I get a nice curved flat. I know it's the way I pull the blade across the belt but I can't figure out what makes the curve and what makes a straight line. I like the way each grind looks but wish I could do it on command and not by trial and error. Any advise is appreciated.
 
You have to focus on pulling the knife through the exact same way. Somewhere along the way you move your hand. You are most likely dropping you hand and not noticing it.
 
Thanks guys. I assume if I apply more pressure towards the tip it would give me a straighter line and less pressure would give me curvature if I am pulling straight. Is that correct? I'll try again tomorrow.
 
Bill I had the same problem on a knife once I chased that line almost all way to the top lol. And I was using my jig so I new the angle was exactly the same. Finally it hit me it was the belt I was using, it was worn more on one than the other. I put a new belt on a the problem went away. I've heard it a hundred times from master smiths to use belts like they were free now I believe it
Jim
 
As Jim said above the belt is worn more on one side. I've flipped belts
over on my grinder at times, usually fixes the problem.
Ken.
 
If the platten is different radius on the sides, or the tracking to one side or the other, could do it too. If your like me, it mostly operator error! ;)
 
Bill, let us know what you find out. I had issues with a belt worn more on one side. Some use wearing on one side as a tool, purposefully wearing it with a piece of wood or mild steel. I've seen it done to start plunges.

The whole "as if they were free" thing has not been lost on me. At least not lately. I bought more belts when I figured mine were half through and the quality of the cut with the new ones, compared side by side, is extremely evident. I can still use "old" belts for other things, but a fresh belt is *really* nice.
 
The gator backs are really bad about this. There great belts but you grid on the edge of a blade and you've ruined it for any other kind of grinding.
 
Here is what I have found. All of you are right! I was using a gator belt and the edges were worn. I also noticed that I tend to use more of the belt on the side where I would get the pointed grind line. What I think this does when the belt edges are worn is that my blade is running on good belt surface towards the center of the belt. I assume this causes more grinding from the tip inward and less grind closer to the ricasso. I put a new bellt on and was able to get good grind lines on both sides by concentrating on these issues. Does this sound logical, or did I get lucky and do something right that I didn't realize?

1. I also backed the platten of the belt to about a 16th to reduce friction. It was very snug before I backed it off. What is the recommended distance for this?
2. How much of the of belt do you use when grinding?
3. Do you run the belt even with the edges of the platten or do you bring it out over the edge when grinding, (I know to bring it out when making the plung)? If so, how much?

Thanks for your help!
 
I'm really inexperienced with a belt grinder, so probably shouldn't even be commenting, but I've noticed something recently.

For a long while I was trying to do my grinding by eye. I realized later that going by feel is critical. Only problem left was that I was grinding on the edge of the belt, so now I try to grind by feel, but also watch the spark pattern. It's simple but as soon as I did this my grinds improved.

Not to be self deprecating, but I've got a loooot to learn. A combination of relaxing but still paying close attention, if that makes sense, has been an (admittedly small), game changer.

Maybe something you already do.

Edit- aside from the plunge I run the belt squared up.

Oh, and when I asked about the belt riding the platen a while back, I was told that you should run the platen just proud of the idlers. So that's what I do.
 
I find that using s wooden push stick helps keep even pressure on the blade. I use a wood block 2" wide and about 4" long rounded on the back end to fit my hand. I cut a 45 degree bevel on front and then squared it off so that there is about 1/4"x 2" in contact with the blade. I try to keep this stationary and even with the belt. Gently position the blade against the running belt. When you have full contact with the blade and belt all the way across then slowly apply pressure with the block and start pulling the blade across.
 
Grinder height and the way I was holding blades at first gave me some pretty wonky grind lines. Best advice I ever got was to tuck your elbows into your body and keep your wrists straight. If you grind at arm's length you have a lot less control than if you're moving your body as a whole. If you set your grinder up with the platen height right above your belt you can also look down and get a better view of the spark pattern like Strigamort suggested. Trying to grind while you're fighting your own posture is just asking for a backache. They say the worst vice is advice, but even the old timers are still learning. Luck to you, sir.
 
The biggest effect I've seen on plunge line shape is how far the belt is hanging off the edge. If the belt is hanging 1/16", 3/32", or 1/8" off the edge, each of those will make significantly different plunge line shapes. When the belt is almost dead flush with the wheel/platen, that will make the straightest plunge line. When it is hanging off, it flexes a bit more, and your plunge can be too soft and unpredictable. I find the best position is just slightly hanging off the edge, so it makes a good straight plunge but with a soft rounded profile.

Structured belts are a bit stiffer as well, so I need to hang them off a pinch more than I would a soft belt like a J-Flex.
 
Grinding is all about PRESSURE.... and PRACTICE (so you know and understand where/how/why/when to apply the pressure). ;) :)

If you apply it more, or less, in one area or another, the grinds won't be even.

IF you have a good belt, a quality grinder, a platen that's trued-up (or contact wheel that runs true), and an even amount of "overhang" with your belt---THEN the only thing that will keep the grinds symmetrical- is even pressure.



One thing that a lot of guys don't notice, is their platen isn't truly perpendicular to the base of the machine/floor. If your flat platen is canted just a bit from top to bottom, you will never be able to get the belt to overhang the edge evenly.



The bottom line (and it sucks) is the only way to get good at grinding is to spend time doing it. Getting hands on help from a SKILLED maker can shave off a LOT of time. Some folks manage to pick it up after a handful of blades. Some are like me and ruin a whole lot of steel before feeling the slightest bit of confidence at the grinder. :foot:
 
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