Help!!!!!!!

T

Taz

Knifemaker / Craftsman / Service Provider
Joined
Apr 28, 1999
Messages
2,565
Well, I was polishing up a few knives this afternoon and noticed something. About 1" (the width of my belt) from the plunge cut, there is a groove in the blade and the blade from the plunge cut to the groove is noticably thicker than the rest of the blade. What causes this and how do I fix it? I am flat grinding the blades on a 1X30 sander with the platen. How will this affect the heat treat? Paul Bos, will this mess up a heat treat?? Everyone, please let me know how to fix this. Thanx!
 
Sounds like you held the blade in the same spot too long. Just eliminate the groove and then make a complete pass to even things out. Hope this helps.

Marcel
 
i've been trying to eliminate the groove, but nothing has worked. I went back to 50 grit belts and kept the blade moving, but the groove is still there and doesn't get better, no matter how much I grind.
 
I am not trying to be mean to you. One way to true up your blade is to draw-file it. Like the oldtimers did before electric grinders. I only rough grind a blade on my Bader, followed by draw-filing to final specifications. Last hand rub with wet/dry
sandpaper. I forge all my blades so there is not much to grind and clean up.

BlacksmithRick@aol.com

 
Originally posted by Taz:
the blade from the plunge cut to the groove is noticably thicker than the rest of the blade. What causes this and how do I fix it? [/b]
Click to expand...
Taz,
Sounds like you need to grind harder from just before the groove to the ricasso/plunge cut. It can be hard to get rid of that groove I get the same thing once in a while, sometimes you can get it out by changing directions when grinding if all else fails hand sand it out with 100grit going lengthwise,but it would be much easier to do on the grinder , depends on how much width you have left on the blade.The trick is to only grind hard from the grove to the plunge when you get it evened out you have to make evenly presured passes over the whole thing.
Hope that helps.
Belock


[This message has been edited by Belock (edited 07-09-2000).]
 
what you have is called a two inch line on a 2x72" sander, and it will come out...its just deeper than you think....one way to avoid it is to only grind in one direction, out...but the main reason you get them is : one, not holding the blade perfectly square to the platen (and its near to impossible believe me) and two...leaving it at the grind start too long.....wish i could tell you more, the advice given above is right one....turn the blade at a forty five and grind away......good luck.

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http://www.mayoknives.com


 
On a flat ground blade you can hold it a 45 degree angle or do some hand sanding. To hand sand, get a piece of wood or micarta and start with 180 or 220 grit wrapped around the piece. I use shop roll but any silicon carbide sandpaper will work.

When you do this sand the ENTIRE length of the blade and go lengthwise until the grindline is no longer visible. If you try to sand just the area of the grindline, then you will get a very thin section right around where the line was (experience talking here) and it will look "wavy". Yes, even on a flat grind. Then go with a finer and finer grit at different angles. It actually doesn't take too long. I also use a cutting fluid such as Tap Magic when I do this. Caution must be observed. The easiest way is to place the blade in a vise just don't impale yourself. When you aren't actually working on the blade, take the darn thing out of the vise.

Craig
 
I'm gonna let my ignorance hang out. What is a plunge cut? I keep hearing about them and dont know if I'm missing a good trick or if I do it and didn't know it had a fancy name. Or mabey it because I hollow grind only?
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Thanks
Leonard
 
Thanks for the replies, guys! I think I got it because I held it at the plunge too long to cut that. The plunge is where the grind starts near the handle. You will get it when you hollow grind, too. I got this line on my uncles knife, but I didn't use the platen on it, so the groove wasn't as deep. I got that out by grinding on a angle. I will try the files a little, but I am trying to get away from them. I did a few totally by files and polishing them was a pain because they had some deep file scratches. The belt doesn't exactly match up to the platen, so the plunge cuts don't match up. Also, the back of the spine is uneven, one of my bevels is longer and shallower than the other, thanks to me trying to get the groove out. How much will this affect the Heat treat or should I try to even out the bevels on the back of the knife?
 
Thanks, I guess my question is are you making the plunge cut as an initial bevel then grinding the rest of the blade to match it or just grinding the blade evenly and this is simply a "by-product" My reason for asking is that I've never had a problem with this "2 inch mark" that others seem to have.

Thanks again
Leonard
 
Well, I was grinding the whole blade as one and not worrying about the plunge, but then decided I wanted to try it, so I cut the plunge in by holding the blade in the same spot for a few seconds to cut it, then I went back to grinding the whole blade as one and just kept the plunge. Could this be why I got the groove? holding the blade in place too long? I am a newbie, it is my first flat ground blade and 2 total blade of A-2. I have 3 of 0-1, but those don't count! I am a newbie, so if anyone has any tips, let me know!!
 
Yea, I would say that's why.

One thing I noticed, you said something about the back of the spine not being even...

IMHO, a professional flat grind is one that goes just to the spine, but does not go past.

You might want to sand the flats. You will lose some thickness, but will regain a chance to keep the top of the grinds even.

Just something kind of hanging off the subject at hand.
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Good luck,
Nick
 
Dave Ellis ABS, Mastersmith here- It sounds like a definite 2" mark (or in your case a 1" mark). A wider belt (2") will make your job easier. Whatever the width of belt do not ever hold the plunge cut against the platen for more than enough time to start your plungecut. also when flatgrinding be sure that your pressure is put on the portion being ground not on the tip of the blade. If you push the tip on one side of the platen and the ricasso on the other with just a bit of force flat on the platen you will dish out the piece leaving your marks. Only way to remove is to even up the flat grind with a course (50 grit or so) belt. Light pressure and keep the piece ,moving. Feel free to contact me.
Dave Ellis, ABS, M.S. http://www.mastersmith.com

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