Progressive grinding for the perfect flat grind.

Fred.Rowe

Fred.Rowe

Knifemaker / Craftsman / Service Provider
Joined
May 2, 2004
Messages
6,848
Grinding the bevels on a blade, while changing the angles of approach or Progressive grinding. There are several benefits to this method.





I used a 4 inch by 2 1/4inch by 5/16 inch section of planer blade for this demonstration.
The first picture shows the blade section, end on, before it was ground.

seconds.jpg


The second and third pics show a 10 degree grind on the left side of the blade.
seconds_jpg1.jpg


seconds_jpg2.jpg


The forth picture shows the results of switching to a 5 degree angle of approach. The grind moves up the blade and moves to intersect the edge that was ground at ten degrees.
seconds_jpg3.jpg


This next picture shows the grind at 4 degrees angle of approach, the grind moves up the blade and moves to intersect the edge.



seconds_jpg4.jpg


I jumped from a 4 degree angle to an angle of 2 1/2 degrees to show the amount of grind line change caused by changing the angle of approach by 1 1/2 degrees.

The last picture shows the grind at the 21/2 degree grinding angle.
As you can see the grind has gone completely across the 21/4 inch blade section.

seconds_jpg5.jpg


seconds_jpg6.jpg
The straight edge shows the ground side to be perfectly level across the flat.

When you grind blades by degrees, two things will happen, one is the grind goes faster because you are grinding across the high points left by the previous angle of approach. The second is you will end up with a perfectly flat bevel.

Happy grinding, Fred
 
Last edited:
Fred

I'm interested - but I have an IQ of 34. I have no idea what you just said. Can you 'dumb it down' a bit? :( Are you adjusting your platen to the degree required - and how can you do that within 1/2 a degree?

Thanks

Rob!
 
Makes sense. That's how I do every flat grind I make, just without the jig. I really need to pick up one of your bubble jigs after the holidays to give it a try.

--nathan
 
silver_pilate said:
Makes sense. That's how I do every flat grind I make, just without the jig. I really need to pick up one of your bubble jigs after the holidays to give it a try.

--nathan
Click to expand...

The technique is not new or my invention by any means; using the jig just makes the process easier and more controlled so the finished grind always turns out the same.

Mike Krall said:
Fred,

Is there a time the video is going to be ready?

Mike
Click to expand...

We are working on getting a better video out that shows the grinding process, using the Bubble jig more clearly. The first one was a little rough.:)

DrThunder88 said:
Do you switch to finer belts as the progression nears completion?
Click to expand...

I continue to use a 50 grit ceramic belt until the bevels are flat, then I switch to finer grits.
 
Fred, your jig is a great tool to improve consistency and train the motor patterns needed for great grinds. I can definitely see it being a help to new and old makers. Way to go for getting the idea put into reality.

I think this post can help some newer makers figure out the idea of walking a bevel up to the spine in flat grinding. I know it would have helped me when I first started to see it demonstrated so.

--nathan
 
silver_pilate said:
Fred, your jig is a great tool to improve consistency and train the motor patterns needed for great grinds. I can definitely see it being a help to new and old makers. Way to go for getting the idea put into reality.

I think this post can help some newer makers figure out the idea of walking a bevel up to the spine in flat grinding. I know it would have helped me when I first started to see it demonstrated so.

--nathan
Click to expand...

Thanks Nathan!

It is just that, a great guide or teaching tool. I can't imagine how many people quit grinding, from frustration at not being able to grind a decent blade, when starting out.
It is very satisfying to me, personally, when someone gets back with me, after grinding with the jig and telling me of their successes with plans to take on more challenging projects.




Happy grinding, Fred
 
Fred I played with the jig a little bit the other night without even having my glass platen set up on my little 2x42 grinder. Just used the junky metal one that is in place to see what it was like. I didn't grind too much but enough to get a feel for the jig and able to make the grinds with the bubble centered at least. And that was only my second time ever in front of a grinder. I can't wait to actually try doing a knife on it :thumbup:
 
Fletch Helical said:
Fred I played with the jig a little bit the other night without even having my glass platen set up on my little 2x42 grinder. Just used the junky metal one that is in place to see what it was like. I didn't grind too much but enough to get a feel for the jig and able to make the grinds with the bubble centered at least. And that was only my second time ever in front of a grinder. I can't wait to actually try doing a knife on it :thumbup:
Click to expand...

Thats great to hear. It wont take you long once you get your grinder set the way you want it; you'll be turning out blades you'll be proud to say you made.

Fred
 
You must log in or register to reply here.
Back
Top