Really need some blade grinding advice guys.

J

J S Machine

Joined
Oct 15, 2007
Messages
72
I\'m making a liner lock folder as my first knife. I posted some pictures of it\'s progress about a week ago.I have posted two or three topics on hollow grinding and different blade finishing subjects. I haven\'t found anything that I can really use, other than a couple of very faint pictures. -and that was when I googled \"hollow grinding fixtures\"...

I bought a small low speed wet grinder, for doing finish work. I guess that would prolly be what its best for. It has a fine grain rock, about 1.5 inches wide and about 8 inches in diameter. I have tried free handing the blade on this setup and I cant get anything close to what would be good enough for my standards or anyone else\'s....Every time I touch the blade to the rock, I get a new impression in a different position and location of the last one. I can go ahead and say there is no way I\'m gonna be able to do it free handed. I don\'t want a flat ground edge, because I know that hollow ground would be much better.---Of course I\'m going to rough it in close, heat treat it, and then finish grind it...

I\'m just kind of frustrated, because I have made everything else look really good. I am almost through with everything except for a couple of small details. The handle inserts are done, and really all i need is to grind the blade so that I can fit it in the handles and adjust everything else for a good clearance.

My problem is that the blade has a contour, like most knives do...and I can\'t figure out how to make any sort of fixture to follow that contour. I almost thought I had it figured out on a surface grinder untill I realized that once the blade starts to curve up, I could not follow that traveling in one axis lol. I need some sort of rotary table or some sort of jig...help me out guys....I don\'t want to have to send it to anyone to do it, cause I want to be able to say that I built the whole thing.

I never really new it could get so complex but this knife has 21 parts so far...

I would really apreaciate your hints on how I could go about grinding this blade, because That is really all I need to get the knife finished.

I also want to get the handles anodized, but I don\'t know of anyone who does that. Anybody know where I could get this done and how much it would cost?
 
Hi, I'm not sure what else you've gotten for how to hollow grind, but you'll want to set one channel, all the way across and set it deep, then you can let the blade fall back into the same channel and widen it. You'll get a lot of slip on a dull belt so I think then same thing will happen on your wheel. You probably do not want to grind on that wheel. Your best bet will be to either flat/convex grind your blade or get a different tool for the job.

I don't grind with a jig or fixture, so I don't really know how to help there. Grinding is one of those things where practice really does make perfect.

What's wrong with flat or convex grinding the blade?
 
I really like the look of a hollow grind, and I just think it would be a good choice. I know I can do it if I try, and if I figure out the best way. I will post some pictures tonight when I get to my my house where I can take some pictures of it. I will show you all in the pictures what I\'m trying to do--and you all can also see the progress on the knife itself.

I have heard that most people who hollow grind do it by hand. All I can say about that is man they are talented...!
 
I really like the look of a hollow grind, and I just think it would be a good choice. I know I can do it if I try, and if I figure out the best way. I will post some pictures tonight when I get to my my house where I can take some pictures of it. I will show you all in the pictures what I\'m trying to do--and you all can also see the progress on the knife itself.

I have heard that most people who hollow grind do it by hand. All I can say about that is man they are talented...!
 
Hollow grinding is not that big of a deal. As previously mentioned, you get a channel started well, and the blade goes right to it. You pressure the blade as you grind in the direction you need to move your grind. It does take a little practice, but my first was as good as my last. I did all hollow grinding for a few years, but finally decided that I didn't like hollow ground blades, and quit. If you're set on hollow grinding, your best grind will be from spine to edge, with the appropriate size wheel for the width of the blade. That is one secret of it all. The right diameter wheel for the width of your grind.
 
You're making these parts on a CNC mill no? Set the bevel on the mill, then follow that bevel off hand on your grinder. It can be done, very nicely, by hand.
 
Ok guys here are some updated pics with the progress. as you can see I have blue layout die on the blade. There is a line scribed close to the center of the blade going all the way from the handle to the tip. I want my bevel edge to stop about half way up. I have the rock dimensions listed above in the inital post. If that isn't what I need, What do you all recomend? I guess I also need to grind some tapered angles from the top of the blade down to the point, to establish the point.

I left the wood inserts at work, was gonna bring those and get them in the pictures too, but I forgot. The blade is about .130 thick right now, but it will prolly turn out to be a little under 1/8" when its done after final grinding. The thumb stud is nothing but a cut off drill for now. When I finish the blade I will prolly make one out of two pieces that can screw in and connect from either side of the blade. Everything still looks a little rough, I haven't cleaned up much of it yet to give it the look it will have when its done. I guess I'm making pretty good progress though. Thanks for the help.

http://i226.photobucket.com/albums/dd198/JSMachine/13.jpg
http://i226.photobucket.com/albums/dd198/JSMachine/12.jpg
http://i226.photobucket.com/albums/dd198/JSMachine/11.jpg
http://i226.photobucket.com/albums/dd198/JSMachine/10.jpg
http://i226.photobucket.com/albums/dd198/JSMachine/9.jpg
http://i226.photobucket.com/albums/dd198/JSMachine/8.jpg
 
why not machine the hollow grind? you seem to know your way around a milling machine. and i know that anything you can dream of as far as mill cutters exists. id say stick with what you know to complete such a good lookin first knife. then go through the learning process and try new things on scrap and or some practice blades. good work, i admire nice machine work, i have trouble processing numbers, so i weld and smith. no machining for me, unless im eyeballing it ;)
-Lou
 
J S
When I first started making knives, I used a bench grinder. I found that the grit of the wheel made a difference as well as how dressed the wheel was. It was very important to have the wheel turn as true as possible. This reduces chatter and bouncing, which an uneven wheel can produce a lot of. The rotational speed can also make a difference. I would definitely stay at 1750 RPM or less. I also always ground into the grind line, by having the cutting edge facing up. I found it was easier to watch the line and keep it linear. It was also easier to avoid washing the line out by over riding it. I also had my grinding wheel on an arbor so that I could run the blade from the left and right with equal visual contact. (yes I had some guards missing, but being able to see was more important.) I had a home made stand to support the shaft that the grinding wheels were mounted on. I did my rough grinding with a 80 grit wheel, and used a 150 grit for final grinding and they were 8" diameter wheels. As another mentioned during initial grinding I established a groove that the contour of the wheel fit into and was able to use ito as a guide to run the grind the length of the blade. My blades were about 1.5 inches wide and the hollow was about an inch wide. I got good grind lines first and then blended the cutting edge into the rest. Used a lot of hand sanding also. Your hollow appears to be closer to .75 " and so the diameter of your grinding wheel may need adjusting. I would think maybe a 6" wheel might work or an 8" could minimize the amount of blending needed at the cutting edge. It looks like you really have a pretty good start grinding, and as others mentioned practice practice practice. Try locking your elbo's into the side between your waist between the bottom of your rib cage and your hip bone to help steady your hands. I hope this gives you some options to look at, using bench grinders is a much harder way to grind, I know that, that is why I invested in a belt grinder.
 
J S Machine said:
Ok guys here are some updated pics with the progress. as you can see I have blue layout die on the blade. There is a line scribed close to the center of the blade going all the way from the handle to the tip. I want my bevel edge to stop about half way up. I have the rock dimensions listed above in the inital post. If that isn't what I need, What do you all recomend? I guess I also need to grind some tapered angles from the top of the blade down to the point, to establish the point.


http://i226.photobucket.com/albums/dd198/JSMachine/13.jpg
http://i226.photobucket.com/albums/dd198/JSMachine/12.jpg
http://i226.photobucket.com/albums/dd198/JSMachine/11.jpg
http://i226.photobucket.com/albums/dd198/JSMachine/10.jpg
http://i226.photobucket.com/albums/dd198/JSMachine/9.jpg
http://i226.photobucket.com/albums/dd198/JSMachine/8.jpg
Click to expand...


I think I might see the problem.

13.jpg



You may not be approaching your grind lines quite right. Generally speaking the grind line is a reflection of edge profile, yours is straight. The main grind should sweep along the tip too, not go straight to the tip. (don't worry, you'll still get that cool line, but that comes later)

The line you have drawn, that goes to the tip, becomes the result where the false edge meets the main bevel. You are trying to stay below that line in your grind, which isn't the way to approach this. Does that make any sense?

The trick to off hand grinding anything is a clear mental picture of the geometry you're trying to get. I think you need to give some thought to what is the real geometry you're going for.

Anyway, you won't need to taper the tip, that will happen as a natural result of the main bevel wrapping around the tip, then adding the false edge.
 
I agree with the above poster. You are grinding wrong. Your grind line should always follow your blade profile unless you are doing some weird reinforced tip. If your false edge AND main bevel both follow the blade profiles top and bottom, you will end up with a straight line where they meet.

Thank about a normal double ground dagger. Two bevels, top and bottom. If you only ground to the center line on each bevel, you would have no distal taper whatsoever and the thickness of the blade would be the full stock thickness right up to the point.
 
Thank you for yall's responses. It hit me like a ton of bricks today what yall were saying. I realized I was grinding it wrong and that I should be following the contour of the edge (or where the edge will be). It also hit me that the look that I am looking for, as someone stated above, will eventually come out once the blade is close to being finished, when the false edge meets the other edge.

Just to clarify some things, none of the parts to this knife were made in a cnc machine. I used a manual mill to cut down the handle material to around .125" and then after that scribed lines around my liners, sawed out the rough cuts and then ground everything in to the liners. the pockets were also done in a manual mill of course with a small cutter, I think I used a 1/8 and a 1/16 cutter to do that. that was all by hand (with the mill). I don't have the actual contours to any of this knife in any kind of toolpathing or cad/cam software, so I couldn't machine it in a cnc. I drew the knife up by hand, and then went from there. I wish I would have done it by drawing it in cad/cam and then cnc...lol

When I get a little closer to done, I will post pictures of the original drawing, the templates I cut out of paper, and the wood pieces I made to simmulate the handle to see if I would like the grip design.

For now I think I'm going to go and try to give this "following the edge" thing a try!
 
JS, get hold of a copy of Johnny Stouts video on hollow grinding. Best demonstation for a newbie I've seen.

peter
 
Well guys I think I've got it. I got both sides done. It took me about 2 and a half hours, but i figured it out. still not perfect, but so close its scary... I'll post some pics in a day or two. right now I'm going to bed..my feet are killing me from standing in the same place that long. once I figured out how, and that I could do it, there was no leaving the grinder for any breaks or anything..lol:D
 
It is possible to use the grind lines you have originally drawn on your blade. It will require a couple of additional steps though. You would have to taper the sides of the blade at the point from say a third to half way back on the blade so that the sides taper to a point. Given that you are using a bench grinder, draw filing the sides to a point after rough grinding would be the best approach I think. Just another thought.
 
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