Flat grinding advice

[LARRYZ10]

95% of the knives I have made since I started making knives are hollow ground. I am now flat grinding some blades and I don't like the look of my plunge lines. On the wheel I curl over the belt a bit to dish out the plunge which I think looks great but I am not sure how to get a nice plunge line with the platen. I have two grinders with platens made f D2 and A2 steel by Nathan Carothers.

Should I try to chamfer or radius the edges of my flat platens to get a nicer plunge? If so what method of making them the same do you suggest? I was looking at some video of Salem Straub showing some nice plunge lines on some of his knives but could not tell if his platens were modified. He makes beautiful plunges on his grinds and I would like to attempt the same.

Any advice would be appreciated. Also, before I forget I have noticed that some knife makers start their flat grinds by hollow grinding the blade first. Is this a big advantage and if so should I use a large wheel like the 14 inch? I need some advice . Thank you, Larry Lehman

 

[Frank Niro]

I often will get to 65 or 45 before I get real serious about getting the plunges evened up. I do run these over the edge of the platen. Otherwise, the courser belts make it very difficult to try to get a good job done. I do have them over the edge a bit but just don't get to serious about having them do a good job for me. No, I certainly recommend you do NOT radius the edges. Frank

 

[Nathan the Machinist]

Your A2 platen has an end radius that can be used to clean up your plunge. To use it, you remove the top wheel and angle your platen assembly back and run a J flex belt at low speed. I run the belt forward but most folks have better luck running it backward.

With a little practice this is an excellent way to get clean even plunges that I think is under utilized.

 

[AVigil]

You want a nicer plunge?

Ok...so clamp you file guide about 1/4" ahead of where you want the plunge to start.

Grind your bevels.

Remove file guide and move it back 1/4".

Now lightly start your grind again feathering and blending from the plunge to the flat grind obliterating your original plunge line.

Start at the plunge and work toward your flat then move the blade back up into the start and go forward again checking along the way.

You will get a nice shallow plunge with an nice radius working its way to the flat.

You can then work the flat up toward the spine and stop where you want.

It will look something like this if you grind to the top

 

[C_Claycomb]

I have a Coote onto which I have fitted a 10x2x0.25 glass platen. Actually, I have two platens, one OE and one home made. I used cheap diamond sharpeners to radius the edges. One has a bigger rad than the other and I switch when I change from wanting a long blend to a short one.

I was surprised (bowled over) to learn that Dan Farr achieved his graceful sweeping plunge completely by manually guiding/carving using the edge of a belt over a fairly sharp platen corner. So it can be done.

Something I have been thinking about is following Nick Wheelers method for dealing in his plunges by hand on a sanding block with the desired corner rad.