How Do You Get a Perfect Grind?

B

BLouie

Joined
Dec 14, 2006
Messages
4
Greetings all. I am new to the forum and new to knifemaking as well. I made my first blade yesterday and had a great time grinding a piece of rectangular barstock into something resembling a knife. I know that I will aquire skills with experience but I don't have an experienced mentor so the forum will be my source for tips and tricks of the trade for now.

I have a question from my first experience yesterday. The blade style I was shooting for is a typical drop-point hunter with a flat grind. When making my blade yesterday, I found it difficult to maintain a consistent straight line where the facets develop from material being removed. The result is a line where two facets meet that is almost, but not exactly, straight. I want my blades to look professional. Is there a trick to getting perfect grind lines?
 
Practice, practice, proactice. until you practice enough ti grind them straight outright, that top grind line han be "fixed" by using sandpaper and a hard backing. You can draw file or hand sand to even up any small dips. Depending on how big the dips are, this can be a 5 minute or a 5 hour job ;)
 
Welcome to Shop Talk. Every new maker has the same trouble that you are describing. With enough blades under your belt you will develop the method that works for you. A good grinder is most of it I think. I suggest the KMG. I use a Burr King and love it but if I had to do it over I would buy the KMG variable speed. They are a magnificent piece of equipment and will make anybody look good. The variable speed is a must to reduce hand sanding.
Just keep asking questions here.
Again Welcome
 
Over time I quickly learned how to grind edge up. For some reason it seems easier than grinding edge down. By grinding edge up one can easily see what is going on, and it is easier to make your grind lines to match.

As you grind, keep the blade moving. I make a pass from the tang to the tip and keep repeating this as I profile the grind. Pay attention to where that contact wheel is and don't take off too much at any one spot. Concentrate on taking off an even layer of steel with each pass from tang to point. Turn the knife over and compare each side frequently, and stop and check if you have any doubt at all about how much material you are taking off.

Remember once you have ground material off you cannot put it back on again.
As I grind I work gradually from the edge to the spine, with each pass- again from tang to point. Pay attention to the point, it is very easy to take off too much too soon. I generally use less pressure and grind lightly when aproaching the tip because the blade narrows and there is less material to grind near the tip than back near the tang.

Having a good grinder really helps. Right off the start I bought a new Wilton square wheel grinder with an 8 inch wheel and some small wheels right down to half inch. A year later I added a 10 wheel and bought the DC controlled motor kit for variable speed. DC controlled variable speed is definitely the way to go. Not only does it improve you work, it makes knifemaking much more enjoyable.
 
Also, make sure you're applying even pressure. You can tell if you are by where the sparks are coming off of the belt. I find that I have trouble with this and have tended to use the edge of my platen rather than the full width of it. Once I started paying attention to the spark trail and adjusting, my grinds started to get better.

Other than that, get some steel and screw it up! :)

You may also want to try grinding practice on paint stirrers or some similar sized wood. It's a lot cheaper and doesn't eat belts like steel does.

-d
 
Yes,
you do need to practice, But to make your first blade a sucess, you can use a flat file to clean the flats to your satisfaction. Load the file with chalk before you start.
Del
 
Thanks for the pointers! I've got the knifemaking bug and really want to produce something I can be proud of.

I went to Texas Knifemakers Supply at lunch today and picked up some new belts, some practice steel and some scales for mock-ups. I'm learning on my Craftsman 1 x 42" belt grinder, which I know is not ideal but I think I need to hone my skills before I upgrade my technology. I now have a variety of grit level belts for use. Is there a particular grit you recommend when grinding? I'm thinking that a less abrasive belt will be more forgiving.

One other question, when grinding, should I be grinding with the blade edge pointing up (against the belt direction) or down (with the belt direction)? Does it really matter?
 
BLouie said:
Thanks for the pointers! I've got the knifemaking bug and really want to produce something I can be proud of.

I went to Texas Knifemakers Supply at lunch today and picked up some new belts, some practice steel and some scales for mock-ups. I'm learning on my Craftsman 1 x 42" belt grinder, which I know is not ideal but I think I need to hone my skills before I upgrade my technology. I now have a variety of grit level belts for use. Is there a particular grit you recommend when grinding? I'm thinking that a less abrasive belt will be more forgiving.

One other question, when grinding, should I be grinding with the blade edge pointing up (against the belt direction) or down (with the belt direction)? Does it really matter?
Click to expand...

I started with a Grizzly 1" x 42". If you take your time you can turn out some pretty good knives with one, but most likely you will need to do some handwork to correct mistakes. The problem I always had was the narrow 1" platen made it very difficult to keep the blade flat with the belt running at high speed. Furthermore, it was almost impossible to get the belt to roll around the edge of the platen and form a nice plunge. While finer grits are more forgiving, they will not remove metal very fast on the small grinder. I would start with some 50 grit and maybe even some 36 grit for initial shaping.

Learn to grind with the cutting edge up and perpendicular to the belt. You want the plane of rotation moving into the cutting edge. Before investing in a higher end grinder, get some files and a good filing jig. A small, rat-tail file and a good filing jig can do wonders for the plunge cuts when you are a beginner. Good flat files can solve a lot of your grinding problems if you are patient. Have lots of sandpaper around, preferably all wet-dry. My recommendation for a beginner is 150 - 600 grit.
 
You might also try making a 9" disc grinder. I use mine all the time to even things up and get rid of course grind lines before hand finishing. A machinist I know made the steel disc for me (I'm sure you can buy them somewhere). It's run direct off the shaft of a 3/4 hp 1725 rpm industrial motor (1ph, 115V) and wired through a 3 position drum switch (to make it reversible). Just use regular 9x11 sheets (220 - 1200 grit) on either the steel plate by itself (for sharp lines) or a cork backer (for soft lines).If I remember right it cost me about $300 to build (Canadian $ mind you). The only limitation is that you can't use it on hollow grinds. Anyway, don't know what everyone else thinks, but that's what works for me.
 
BLouie said:
Thanks for the pointers! I've got the knifemaking bug and really want to produce something I can be proud of.

I went to Texas Knifemakers Supply at lunch today and picked up some new belts, some practice steel and some scales for mock-ups. I'm learning on my Craftsman 1 x 42" belt grinder, which I know is not ideal but I think I need to hone my skills before I upgrade my technology. I now have a variety of grit level belts for use. Is there a particular grit you recommend when grinding? I'm thinking that a less abrasive belt will be more forgiving.

One other question, when grinding, should I be grinding with the blade edge pointing up (against the belt direction) or down (with the belt direction)? Does it really matter?
Click to expand...

Send me an email, I am in the Houston area.

Craig
 
I worked on blade #2 last night and the experience is helping. I'm still not getting the flat facets I was hoping for, instead I'm getting a subtly rounded convex shape. Probably the result of trying to use the slack portion of the belt to grind away the visible imperfections from my flat grinding work. A few things I'm catching on to:

- Finger grooves are difficult, if not impossible, to cut effectively on my grinder.
- Concave curves would be best cut against a wheel rather than on a slack-belt or edge of the platen.
- A band saw would be nice so I could cut the basic profile. Grinding rectangular stock into shape is time consuming.
- Go lighly on near blade tip as it doesn't take much to discolor the tip with excessive heat.

Any other pointers would be appreciated.
 
BLouie said:
- A band saw would be nice so I could cut the basic profile. Grinding rectangular stock into shape is time consuming.


Any other pointers would be appreciated.
Click to expand...

A hacksaw will work just as well as a bandsaw, and save you $$ on belts to boot.

-d
 
BLouie said:
Thanks for the pointers! I've got the knifemaking bug and really want to produce something I can be proud of.

I went to Texas Knifemakers Supply at lunch today and picked up some new belts, some practice steel and some scales for mock-ups. I'm learning on my Craftsman 1 x 42" belt grinder, which I know is not ideal but I think I need to hone my skills before I upgrade my technology. I now have a variety of grit level belts for use. Is there a particular grit you recommend when grinding? I'm thinking that a less abrasive belt will be more forgiving.

One other question, when grinding, should I be grinding with the blade edge pointing up (against the belt direction) or down (with the belt direction)? Does it really matter?
Click to expand...

i think learning on a 1x42 will teach you faster how to make things flat because of how you have to fight to do so
i just got a KMG and love it i have just a few knives finished using it so if you look at some of my posts (or my site) you can see you jsut need to work at it (i used that 1x42 for 3 years)
i have never used a file to clean up a grind line if it was off more then 400 grit hand sanding i went back to the grinder
 
I always find these threads interesting. They always make me think i do too much hand work and not enough grinder work......I hate taking something back to the grinder, so usually only go to about 220 on the grinder before i draw file to get a true flat, then hand sand.

Its amazing to see how "not flat" a "perfect" looking grind is once you draw file it.
 
When I'm having trouble getting a flat grind, or perceive that it isn't truly flat I have a method of checking it. From my previously life repairing machine tools, I have a "flat master". It's just a chunk of iron about 10" by 12" square and 1" thick. The surface is flat within .00001". I lightly blue up the surface of the master with bluing paint (basically a very thin oil paint). I then carefully set the blade down on the surface to check how truly flat it is. Any place that the blade surface is high will have blue paint transferred onto it. I then carefully remove the blue paint and a slight amount of steel with a file or my dremel. I clean it all up with acetone and repeat...over and over...until I get a good, solid speckled blue pattern over the entire surface of the blade. I mostly use this on my tangs (I currently make mostly full tang knives). I also check my handle scales this way. But, instead of checking my handle scales on my "master", I've gone to checking them on the knife tang. Basically, this allows me to custom fit the scale to the tang. My fit and finish has improved greatly with this process. I've also learned which parts of my grinding processes don't work and which do. If I've held the tang more towards one side of the platen, and go over and check it on the master, I usually don't get a very good "blue up". But if I feel like I've controlled my grind well and kept it flat against my platen, I usually do get a fairly good "blue up".

This is just some of my procedures. I hope you find it interesting.
 
I've never tried a 2" x 72" grinder. Does it make a big difference?

Lloyd, I like your website. You've made some very nice knives! My favorite is the Bluejeans Santoku.
 
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