Questions about Grinding...

[Normark]

Hey Guys...

Got a question about my grinds...

When I'm getting down to the edge of my grind I notice that the edge goes thick, thin then thich at the tip again.

Is that because I'm not having even pressure all the way across ?

I've been fixing it somewhat by angling the knife on the corner of the wheel and eating away the thickness at the plunge line,, then I eat away at the tip a little then level it out again..

Is there an easier way to do this ??

I'm chisel grinding BTW...

I'm also having problem with keeping my grind shallow and it likes to walk up to the spine, before I get a nice hollow even groove...
I'm using an 8" wheel.

Any help would be Great..

Thanks

Eric
O/ST

 

[TekSec]

Dunno about the hollow grinding, I've never been real successful at that. However, when I flat grind I get the same thing. This has to do where the metal is contacting the belt as wel as pressure. I usually take the thickness down on the plunge end by interrupting my grind after I pass the thick portion. Once I get the proper thickness there, I lightly touch the blade to the belt to set the proper angle and move towards the tip in a smooth motion. Once near the tip, I slow and apply a little more pressure to thin out the tip more. I am slowly with time getting a more even pressure all through the grind and with practice, there will be no need to thin out specific areas. And if I get it a little thin in some places, I just grind the edge by holding the blade to the wheel and lightly grind the edge inwards...of course, this makes a recurve blade sometimes, but I like recurves so it's all good.

 

[Troop]

Dunno about the hollow grinding, I've never been real successful at that. However, when I flat grind I get the same thing. This has to do where the metal is contacting the belt as wel as pressure. I usually take the thickness down on the plunge end by interrupting my grind after I pass the thick portion. Once I get the proper thickness there, I lightly touch the blade to the belt to set the proper angle and move towards the tip in a smooth motion. Once near the tip, I slow and apply a little more pressure to thin out the tip more. I am slowly with time getting a more even pressure all through the grind and with practice, there will be no need to thin out specific areas. And if I get it a little thin in some places, I just grind the edge by holding the blade to the wheel and lightly grind the edge inwards...of course, this makes a recurve blade sometimes, but I like recurves so it's all good.

Ya know, I was getting the "not-on-purpose recurve" thing happening for a while, too.

 

[TekSec]

Hey, ya gotta do what ya gotta do

 

[Karl B. Andersen]

That first part of your grind is simply how much TIME the belt is in contact with the blade! As you begin your grind, the portion of the blade you are in contact with only gets touched by the very edge of the belt. With the remainder of your grind, the blade passes over the entire width of the belt. Did that make sense?
You may have to hesitate for a brief moment at the beginning of your pass so that the first portion gets the same amount of stock removal as the latter portions.
The tip is simply a different geometry. You will have to gently drop your elbow a little and gently tilt the tip in - easy now!
As far as the depth/height of your hollow grind - TAKE YOUR TIME!!! Feel that hollow you are creating. Let the Force be with you.
Don't rush it.
Watch that little black space between the blade edge and the wheel face, and use that as your guide.
Feel that wheel in there.
Check your blade with each pass. If you see you are getting higher than you like, pull that spine out away frm the wheel!
Ever hear the joke about the guy who walked into the Doctor's office, raised his arm over his head and says, "Hey, Doc, it hurts whenever I do this."
The Doctor says, "Then don't do that."
That's what I'm sayin' - if your grind is getting too high, then don't do that.

 

[AcridSaint]

Hi Eric, next time you start to grind, watch yourself closely when you come off the tip. I would imagine that you're tilting it in at the end, probably when you come off the wheel. Try making a conscious effort to pull straight back off the wheel before you ever get close to coming off the edge. Also, if you're starting your grind at the plunge and pulling toward the tip (the way I grind and I think most others), you can push back to the plunge on the same pass with more pressure and it will often take more material out toward the plunge.

With an 8" wheel you should be able to set your hollow in the first couple passes. I knock the edge off at a 45 with the first pass, use the next two passes to start the grind and the fourth one I usually put a good deal of pressure on to set the hollow. After that pass, the wheel usually should fall back into the channel.

Hope that helps.

 

[Lynn]

Eric,
I have found that if I contact the wheel just before where I want to stop the grind, (using a very light pressure) then move back to grind line before starting a full pass, that it makes for more even grinding. Sorry about the awkward sentence. Look at the grind on every pass and readjust to keep it even.
If you are having trouble with control don't use 36 grit. 80 is plenty and will work fast. If that gives you less than what you want move on to 120. The point is that I make my mistakes slower and easier to correct with another pass.
Just what I do,
Lynn

 

[Bufford]

Hi Eric:
Pay attention to each pass you make on the grinder. To keep things even from the tang to the tip, start by making an even grind from your very first pass. It is easier to keep the grind even from the beginning than it is to start compensating for an uneven grind later. Problems tend to start small and grow bigger later.

The tendency is there to take off more material in the middle of the blade than at the tip or tang. Be aware of where the belt is, how much pressure is being applied, and the amount of time the belt is at any one place on the knife.

It is best to develop a fluid like motion and as you hollow grind, move the grind from the tang to tip in one motion. As one nears the tip, during that last inch or two of travel down the blade reduce your pressure to compensate for the amount of steel in contact with the blade as there is less and less steel as one aproaches the tip. Always keep the blade moving, to avoid creating dips and dimples in the blade.

Shop lights do not lie. After each pass or two shine the grind in the light to check for even grind. It is easier to correct problems when they are small than it is to leave them later only to find out that there isn't enough steel left to grind out a problem.

Do you grind edge up or edge trailing down? I find that grinding edge up is easier, and that the belly of a hollow grind rides nicely on the contact wheel giving better control.

Variable speed motors help a big deal. I go full speed at first, but as things grind out, I get better control over my grind by slowing the speed down.