Fred Rowe
Well-Known Member
This thread was originally posted in 2009. If you have not seen it previously it contains some good food for thought.
Progressive grinding assures that as you grind up the blade the abrasive will make contact with the peak left by the last grinding angle. The steel is removed faster each time the angle of approach changes.
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.
The second and third pics shows the grind on the left side of the blade using an angle of approach of 10 degrees.
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.
This next picture shows the grind at 4 degrees angle of approach, the grind moves up the blade and moves to intersect the edge.
I jumped from a 4 degree angle to an angle of 2 1/2 degrees, relative to the belt surface, 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 2 1/2 degree grinding angle.
As you can see the grind has gone completely across the 21/4 inch blade section.
The straight edge shows the ground side to be perfectly flat across the ground bevel.
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.
So whether you want a flat scandi grind blade, ground at 12 degrees or a wide chopper, three inches across, ground @ 2 degrees we are all looking for the same results, flat even bevels.
If you have questions send me a pm, happy to answer any questions you might have.
Happy grinding, Fred
Progressive grinding assures that as you grind up the blade the abrasive will make contact with the peak left by the last grinding angle. The steel is removed faster each time the angle of approach changes.
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.
The second and third pics shows the grind on the left side of the blade using an angle of approach of 10 degrees.
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.
This next picture shows the grind at 4 degrees angle of approach, the grind moves up the blade and moves to intersect the edge.
I jumped from a 4 degree angle to an angle of 2 1/2 degrees, relative to the belt surface, 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 2 1/2 degree grinding angle.
As you can see the grind has gone completely across the 21/4 inch blade section.
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.
So whether you want a flat scandi grind blade, ground at 12 degrees or a wide chopper, three inches across, ground @ 2 degrees we are all looking for the same results, flat even bevels.
If you have questions send me a pm, happy to answer any questions you might have.
Happy grinding, Fred
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