Thomas,
Would it be possible for you to share your calculations on this? A diagram to describe the calculations would be massive too.
This picture really describes a lot but would love to see how you arrived at the 3 and 1.5 degree numbers.
-
The BladeForums.com 2024 Traditional Knife is ready to order! See this thread for details: https://www.bladeforums.com/threads/bladeforums-2024-traditional-knife.2003187/
Price is$300$250 ea (shipped within CONUS). If you live outside the US, I will contact you after your order for extra shipping charges.
Order here: https://www.bladeforums.com/help/2024-traditional/ - Order as many as you like, we have plenty.
Sharpening a convex blade like an Opinel
- Thread starter ckpj99
- Start date
Thomas,
Would it be possible for you to share your calculations on this? A diagram to describe the calculations would be massive too.
This picture really describes a lot but would love to see how you arrived at the 3 and 1.5 degree numbers.
Pinnah,
I shall make some videos in English and increase my English side on my homepage, You must wait for that to happened to see “it” happen.
Basic is my simplest tool and is about 10 years old now. Basic have a bended guide rod (not angled) and Basic will give you any convex edge when you have learn to handle it.
It is really simple and it works like this:
Basic have a screw as a pivot point. In top of the screw is the pivot loop placed. The screw is size M4, that means that in this distance (te tool is only 9 cm long) 1 full turn is about 33/100 parts of 1 degree = 3 full turns is 1 degree – and half a turn is about 15/100 parts of 1 degree, this on flat edges.
I wright “about” because knives has different blade width – and the blade width change the edge angle. That is why I cannot give you any data or facts. Sure, I can calculate for one blade width – but that means that all other blade widths - will be wrong…
The bended guide rod make a 3 degree convex curve across the edge if you use complete length of the sharpener – but this is not the complete truth, it gives three degrees in just one fixed position = if you grind an edge 3 degree convex – and then change degrees with the pivot screw, you can add 3 more degrees to the convex edge, or 1 degree…depends on how much of the length you use on the sharpener.
If the pivot loop is placed low, the convex sphere, and the edge, will be slightly convex. If you place the loop high you will get a steep angle and also a steep convex sphere.
Basic is a simple tool constructed for 10 years ago and the thougt behind basic was outdoor sharpening. Basic is not a precision tool in degrees…  but Basic is very nice to maintain edges, made in stainless steel, functional in all climates, always. But of cause – Basic is limited to max 12 cm blade length and only parallel blades can be sharpened. (All sharpening tools is limited in one way or another).
The pivot screw was invented because I use many knifes and they all have different edge angles. With this pivot screw Basic can perform 160 different edge angles. This means, in my way of thinking, that I decide the edge angles I like to have on my knifes – not the tool I use. I can adjust the edge angle in steps on 15/100 arts of 1 degree with Basic.
I have made a protractor kit to Basic. Just attach it and now can Basic grind with degrees, blades up to 18 cm blade length can be sharpened – but still only parallel blades.
Today exists Angle Cube and similar tools that can measure how the sharpener moves on a convex edge. It makes it very much simpler to see the convex sphere. Just clamp Basic in a vice, measure how the sharpener moves across the edge, start- and stop point in degrees. That possibility was only a dream for 10 years ago 
Thomas
I shall make some videos in English and increase my English side on my homepage, You must wait for that to happened to see “it” happen.
Basic is my simplest tool and is about 10 years old now. Basic have a bended guide rod (not angled) and Basic will give you any convex edge when you have learn to handle it.
It is really simple and it works like this:
Basic have a screw as a pivot point. In top of the screw is the pivot loop placed. The screw is size M4, that means that in this distance (te tool is only 9 cm long) 1 full turn is about 33/100 parts of 1 degree = 3 full turns is 1 degree – and half a turn is about 15/100 parts of 1 degree, this on flat edges.
I wright “about” because knives has different blade width – and the blade width change the edge angle. That is why I cannot give you any data or facts. Sure, I can calculate for one blade width – but that means that all other blade widths - will be wrong…
The bended guide rod make a 3 degree convex curve across the edge if you use complete length of the sharpener – but this is not the complete truth, it gives three degrees in just one fixed position = if you grind an edge 3 degree convex – and then change degrees with the pivot screw, you can add 3 more degrees to the convex edge, or 1 degree…depends on how much of the length you use on the sharpener.
If the pivot loop is placed low, the convex sphere, and the edge, will be slightly convex. If you place the loop high you will get a steep angle and also a steep convex sphere.
Basic is a simple tool constructed for 10 years ago and the thougt behind basic was outdoor sharpening. Basic is not a precision tool in degrees…  but Basic is very nice to maintain edges, made in stainless steel, functional in all climates, always. But of cause – Basic is limited to max 12 cm blade length and only parallel blades can be sharpened. (All sharpening tools is limited in one way or another).
The pivot screw was invented because I use many knifes and they all have different edge angles. With this pivot screw Basic can perform 160 different edge angles. This means, in my way of thinking, that I decide the edge angles I like to have on my knifes – not the tool I use. I can adjust the edge angle in steps on 15/100 arts of 1 degree with Basic.
I have made a protractor kit to Basic. Just attach it and now can Basic grind with degrees, blades up to 18 cm blade length can be sharpened – but still only parallel blades.
Today exists Angle Cube and similar tools that can measure how the sharpener moves on a convex edge. It makes it very much simpler to see the convex sphere. Just clamp Basic in a vice, measure how the sharpener moves across the edge, start- and stop point in degrees. That possibility was only a dream for 10 years ago 
Thomas