Angles

N

NORSEWOLF

Joined
Sep 8, 2013
Messages
38
Got my KMG up and running.
I woukd like to build some grinding jigs.
I'm not sure of angles or style of jig.
Any advice welcome.

Thanks Norsewolf
 
First thing is get a Wixey.
http://www.rockler.com/wixey-digital-angle-gauge

Square everything up before using any clamp or jig. Use the Wixey to determine angles in jigs, etc. Best $40 you will ever spend.

Basic method to square the belt and work rest -
Set the Wixey on the flat platen.
Zero it. Set on the work rest.
Adjust until it reads 90.9°.
Tighten bolts well and double check readings.
 
I'll order 1 today!

I was wandering what angle to make jig to grind flat grind?
Also for hollow grind?
I have a 10" contact and flat platen.
 
Your angle is defined by the knife's geometry, and that being said, the angle of bevels is not critical....the angle of the edge is critical (when you sharpen). If the knife has a 1/8" spine, and is 1.25" tall, then the bevel is going to be just under 3 degrees. No need to figure the angle when grinding/filing in the bevels.
 
Thanks for that clear answer.
Lite up back yard with the first spark off of my new grinder this afternoon...
 
I'll take the opposite tack and say the primary bevel angles are quite important. The angle chosen dictates what the possibilities are of the actual cutting edge.
Many seasoned makers will tell you; you work towards the cutting edge when you first pick out the stock you are going to work with. Or, the edge starts at the spine of the blade so to speak. Working with 1/4 steel gives different possibilities at the edge than working with 1/8 inch stock. If you wish to reproduce a given blade it is best to know what bevel angles were used as well as the actual cutting edge angle. Good blade geometry calls for proper steel selection with corresponding bevel angles.
If you want to do convex grinds all that goes out the window.
 
Fred makes and sells several sharpening and grinding tools that are excellent for getting accurate angles and grinds. I consider his tools aids, not jigs. They help you learn to grind right.
 
Fred, I agree with what you are saying. But I don't think there are too many knife makers that say, "Hmmmmm....I need my primary bevels to be 2.8 degrees vs 3.2 degrees" or something like that. You are right....the bevel angles are VERY important in the overall geometry of the knife and cutting ability. But for me....I never figure out the actual angle. I carefully choose the thickness/blade height/grind type for the intended purpose.
 
So if i want to make a jig to clamp blade to act as heatsink should i make half.of 3° /what my grind i want?
I am also going to hollow grind on some of my projects with a 10" contact wheel.
Thanks, Norsewolf
 
Norsewolf.....I would love to answer your question, but I don't understand what you are asking. A jig to act as a heat sink? Are you grinding steel that has been hardened already? No need to worry about heat buildup before the heat treat is done, but if it HAS been done...yeah....heat is not our friend.

But as far as the angle to set your jig....again...this depends on your knife geometry. How thick is the knife? How tall is the knife? What kind of geometry do YOU want (super thin for slicing, or a bit thicker for all around use, or thick for chopping)? That determines everything. The example I used of 3 degrees was just that...an example. It may or may not be right for the knife you want to make.
 
Build the jig so you can adjust the angle, or make it 90 degrees and tilt the platen to what you need for the flat grind. Start with more then work your way up / down the blade.

You can get cheap angle finders at your local lowes / hd.
 
I would not even concern myself with what the actual angle of the main bevel is. It is a function of the blade height and the spine thickness. It is what it is. Pick the steel thickness you want for the knife task, and pick the blade width needed for that task....the angle will calculate itself as the bevel is ground. This is the joy of a FFG.

The difference between a 1.25" wide blade that is 1/8" thick vs one that is 1/4" thick is three degrees per side ( roughly 2.5 vs 5.5 degrees). The primary bevel being 5 degrees inclusive vs 11 degrees inclusive will make some difference in knife use, but as Stuart points out, it is the edge angle (which is often four times the primary angle) that will matter most. Even if you are OCD and just have to calculate the main bevel angle,........ the angle changes continuously over the length of the distal taper.
 
I think understand now.
I'll grind a few and see what i like.
I waited till Blade to chose my grinder and wish i had it
Before as now i have more questions.
Hope to a few blades ready for HT soon.

I'm in south Louisiana any HT close to me that y'all know about?
 
samuraistuart said:
Fred, I agree with what you are saying. But I don't think there are too many knife makers that say, "Hmmmmm....I need my primary bevels to be 2.8 degrees vs 3.2 degrees" or something like that. You are right....the bevel angles are VERY important in the overall geometry of the knife and cutting ability. But for me....I never figure out the actual angle. I carefully choose the thickness/blade height/grind type for the intended purpose.
Click to expand...

The vast majority I believe never give it much thought. I've been grinding with the BJ for so long its hard for me not to relate without the angles in my head. Its second nature.
Its not the angle thats important, its the grind and the geometry itself thats important.

One interesting aspect of using a BJ is I can talk to a maker in another state about a blade I'm working on and he can produce the exact same blade grind by me supplying him with the measurements and grind angles that were used.

We are saying the same thing just using different techniques to accomplish the goal.

Regards, Fred
 
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