Curved plunge

[Natlek]

How you would grind this ? Disk sander have big curve for that ?

 

[Lorien]

freehand on the 2x72 is how I'd do it

 

[Joshua Fisher]

I’d grind the plunge last and let 1/4-3/8” of the belt overhang off the platen

 

[Crag the Brewer]

I'm thinking I'd try a small 3" contact wheel. Rotate, and twist the steel as needed

 

[navman]

Carefuly?

 

[Natlek]

freehand on the 2x72 is how I'd do it

I can grind only one side free hand , other side would be failure 100%
I can try with jig , but I am not sure I can get even curve on plunge .Any way , free hand or jig I must hold blade in this position / like on drawing / to get small /red color / radius on plunge .If I grind in normal way on work rest with jig would be easy to get that curve on plunge but it would be too much shallow , like blue color . I want it deep , to be more pronounced ..if I used right word

 

[Natlek]

Carefuly?

*Me* and *carefuly * is very, very bad combination of words in the same sentence

 

[Taz]

You would have to roll the belt off the edge and pull the blade across the platen to get a sweeping radius. I can't do that symmetrically it will take a lot of practice. Maybe use a small wheel and water fall platen or something like that? Kinda like how they clean up integral bolstered knives?

 

[Bühlmann]

Isn’t the further you ride the belt over the edge of the platen the larger the radius of the grind line?

 

[Lorien]

laying everything out first helps a lot with symmetry, for me anyway

 

[Richard338]

I start grinding at the plunge and it starts off with a pretty gentle curve. Later I do a few passes towards the plunge and if I want to square up the plunge I put a little pressure towards the spine. Those passes are best done with a flexible 120 and a little overhang. Usually I leave it a little curved at the top.

 

[J. Hoffman]

Natlek you have the right idea with the angle of the blade. I don't hang the belt off the edge much, just enough to cover the edge of the platen. I start grinding at the tip and work my way back to the plunge line.

 

[Alex Topfer]

Would a platen with a rounded edge help?

 

[Natlek]

Isn’t the further you ride the belt over the edge of the platen the larger the radius of the grind line?

And that's what I want to avoid. I want 3 centimeter radius plunge and a small radius on edge.

 

[Natlek]

I'm thinking I'd try a small 3" contact wheel. Rotate, and twist the steel as needed

Steel is 52100 , 7mm thick for now .It is already thermal cycled and I will HT it to form Bainite and then grind bevels .Long process and I don t want to screw up all that in end .
What I am thinking is this ... what if I grind bevels to that red lines first and then I can make 6 centimeters Dia. disk to grind just that curve ?????

 

[Crag the Brewer]

Steel is 52100 , 7mm thick for now .It is already thermal cycled and I will HT it to form Bainite and then grind bevels .Long process and I don t want to screw up all that in end .
What I am thinking is this ... what if I grind bevels to that red lines first and then I can make 6 centimeters Dia. disk to grind just that curve ?????

I'll try to look for a youtube video for you.....
I have a different idea.

 

[Natlek]

Natlek you have the right idea with the angle of the blade. I don't hang the belt off the edge much, just enough to cover the edge of the platen. I start grinding at the tip and work my way back to the plunge line.

Thanks ! I can set my work rest in that position so I can use grinding jig .But I am not sure I can do it right . I can practice on some mild steel but that is not a guarantee that I will do the same on this steel . I know that from experience
I like that knife !

 

[Crag the Brewer]

100 Percenters presents: Bill Luckett - Part 2 - grinding demo

Demonstration of how 100-percenter Knife Maker, Bill Luckett, freehand grinds his blades on a 3-inch wheel inside his shop in Weatherford, TX

www.google.com

This is what I'm thinking, unless I am misunderstanding what you want?

 

[Natlek]

100 Percenters presents: Bill Luckett - Part 2 - grinding demo

Demonstration of how 100-percenter Knife Maker, Bill Luckett, freehand grinds his blades on a 3-inch wheel inside his shop in Weatherford, TX

www.google.com

This is what I'm thinking, unless I am misunderstanding what you want?

Thanks my friend , but most likely, more steel passed through his hands than money through my hands I don't have the skills to do it and it is not what I am looking for . I want sharpened edge to start as close as possible to plunges
I want plunge like on this knife , but up to the spine ..... In fact, I will try to make the same knife, only full flat grind . Convex is out of question for me right now .

My head is spinning more and more to disc ....I have small but powerful motor with 22 000 RPM and I can make 7cm. Dia . disk .Blade is 35mm wide so half disk will grind that curve perfect .Blade in jig of course .

 

[Richard338]

I think you could better understand the geometry if you had an example on hand and could lay a ruler on the bevel etc.
The shape you want is generally achieved with a flat platen. I think seeing the projection of the plunge you want as curved and thinking about a disc is wrong. You don't want a curved plunge with straight walls.
The curve arises from how quickly the top of the plunge approaches the spine. If it is abrupt, then you get a square plunge. More slowly creates the curve.