Finish grind problem

D

DHackney

Joined
Jul 12, 2004
Messages
178
Hi folks,

It's the newbie pest again :(

I am having a problem with the finish grind on this knife, after the heat treat. I got some backing material (conveyor belt + graphite) installed on the
platen and, even with this, I find that my blade has a lot of little facets on the bevel and I'm not sure what I'm doing wrong. I don't know if the belt seam is the problem or not, but I sure would appreciate your help. I don't want to blow it now after all this work. I'm thinking about doing some hand finishing if I can't get this resolved.

Many thanks, as always!
Dana Hackney
Monument, CO
 
It is not an uncommon problem, you royal PITA pest, asking questions like that! :D ;) :footinmou

First off, it's a good question Dana, 'cuz it's a common problem. Second, I doubt anyone would complain about the questions you ask...

I think this is a common problem to all. My feeling is that it is caused by the "bump" caused when the buttsplice crosses the platen. One can see that cheap belts, or, worst, overlap spliced belts make it even worse. It is exacerbated by the graphite; it is supposed to alleviate the effect but my experience says it makes it worse, especially once it starts to wear.

My comment would be to shuck the current backing and try pyroceram. Also, don't press hard when you finish grind; a delicate touch is in order in fine grits. Third, do enough grinding to get rid of the oxide layer then go to hand finishing. If you are not bothered by a coarser finish, blend the little imperfections with Scotchbrite belts.

What type of belts are you using for finishing work? Some will be more prone to this problem than others.

These are my $0.02 on the topic; someone else will come along with a better solution I hope.
 
for the kind words.

I don't know how I'd get by without this resource - seriously!

I do have a platten that has some of Darren Ellis' pyrochem material on it. I just recently put the other stuff (conveyor belt + Bader graphite layer) on another platen just specifically for the final grind. I guess I'll go back to the pyrochem.

The belts I'm using (400 and 600 grit), I got from Pop's and I believe they are either Norton or Klingspor (sp?).

Thanks again, Mike,
Dana
 
Dana, if for no other purpose than that aggravating faceting, I would strongly recommend testing a Norax belt in at least one and preferably several finishing grits. They are "cushiony" and don't seem to push that splice into the blade as much with each pass.

I still haven't totally bought into the Norax because I haven't found them to have the lifetime I expected for the price. Periodically they need to be run at high speed and a pice of scrap laid into them to refurbish the abrasive. Turning them around and running the other direction has been reported to help, too, once they seem to dull. Nonetheless, i have been impressed with the way they surface steel.

Experiment with belts and pressure and you will eventually discover how far you can go on the machine before you have to turn to hand work. Eventually, if you want the best finish, it'll be by hand regardless. I have yet to find someone who can handrub or mirror polish a blade with a grinder! ;) :D

BTW, you're most welcome, Dana. People wouldn't try to help if they didn't want to......the pay around here sux. :D
 
for the advice. I will look into the Norax belt idea, as well as
try out my hand at hand finishing.

Best regards,
Dana
 
Dana, another consideration for belts may be those Gators. Pop sells em, apparently, and we keep hearing that they leave a great finish. The problem there may be they only go to 400 or so, I can't 'member. Actually, think I'll call Pop and order some so I can see, myself.
 
I just ordered some 'gators' 2 each in the grits Pop sells to try out. They only go to a 360grit equivalent, but it'll be interesting to see how they perform.

Gib, have you noticed whether these things are waterproof? I got surprised when I used the first generation Trizac! :(

Dana, Pop gave me a good tip I wanted to pass on. He said that he found that a lot of chatter marks can be caused by the belt essentially "bunching" under the pressure of the blade, and thus digs divots. He said a lot of that chatter was eliminated when he started using a belt lube. There is a specific sorta waxy-greasy goo sold for belt lubrication, but someone may have a homebrew or alternative you could try without ordering the real deal. I have to dig back into the farthest reaches of my storage cubby. I think I have one in there that's probably 20 years old! LOL

Hope this info helps!
 
Thanks for passing that info on from Pop's. I heard somewhere that WD40 was supposed to help with the lube problem? Maybe it was for heat? Maybe I should just order some from Pop.

Please let me know too, Mike, how these belts perform.

Kind regards,
Dana
 
Dana, thanks for asking all the newbie questions...now I don't have to. :D

Why did you change from the pyroceram to the other platten. Were you getting the same problem with the pyroceram?

Mike, let us know how you like the new belts.
 
Dana, Pop mentioned oil-as-lube, saying he thought it didn't work anywhere near as well as the grease. I remember now why I didn't like the belt lube: I water dip after almost every pass on the grinder, and it got just a little messy for me mixing the two and having stuff stick everywhere. Try it yourself, though; it is relatively cheap and you may find it a godsend. Might be a lot easier than changing the dip bucket in between grits every knife. :)
 
First, Mike, thanks for the additional info from Pop. I think I'll first try dipping more frequently and using the pyrochem platen.

Tom, I'll keep the newbie questions rolling. I've learned more stuff here than I could gather in any other form. Regarding switching to the platen with the conveyor belt+graphite, I was told that this was the way to go for doing the finishing grinds. I don't recall having these problems with the pyrochem, so it'll be back to the pyro and more dipping to see if this remedies the problem.

Thanks again guys,
Dana
 
Mike, I don't know for sure but I heard that thy were. The neat thing about them is the abrasive is real thick and on a couple of hollow grinds I was able to finish the plunge with the edge of the belt without rolling the belt over the edge of the wheel.
You are supposed to be able to dress them for a new grinding surface too. Gib
 
I use the gator belts a lot, and I get great life out of 'em, I've got 'em from 300 to 45 micron, which leaves a finish about like 400 grit, I'd recomend 'em. and they are waterproof from my experience.

Tony
 
If it hasn't already been mentioned above, take the backing off your platen, and replace it with pyroceram. None of those soft backings work well, and cause the type of problems you describe.:eek:
 
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