question from first-time knifemaker, flat grinding bevels on thick blade

[obsessis]

I am making my first knife(s) and I am ready to grind the bevels. I am having a hard time visualizing it, though. My knife is .25" thick and about .75" to 1" wide, 3" to 4" long (two diff. knives). I want to do a V grind and be able to put my secondary bevel to sharpen it at 20 degrees. I assume I'd have to do the primary bevel at 15 d but it would go all of the way up and grind off some of the spine. Does that give a good picture to what my problem is?

I thought about doing it like a frameback straight razor, having the bevel go up 15 d and then stop and then have a fat spine but I might not be able to do that.

What else can I do? Right now I am using a 2x48 vertical belt sander with a platen. There is a contact wheel at the bottom but the motor to the left makes it so I don't think I can use that to hollow grind.

I thought about doing it convex but I don't know how to do that. I think I need a slack belt area? I might have some room on top of the platen to do that.

 

[SBuzek]

What knind of steel?If stainless scribe two lines down the edge about .020 apart and grind a 45 deg starting grind up to those lines then work your grind up the blae to the spine don't worry about the exact angle just try to get the grinds flat.IMHO 1/4" stock is too thick for that narrow a knife,your gonna wind up with someting looking like a chisel.
Agood deep hollow grind might work but as you stated not really doable for you.
Stan

 

[obsessis]

It is a bit too thick to do without hollow grinding but I'm going to try to do it anyways.

Any other advice? Tips on how to convex or if it'd even be a good idea?

 

[silver_pilate]

When I started out, I was all hung up on exact angles as well. However, that's just not how it's done unless you are a milling or CNC machine.

If you start with a known thickness of steel and grind bevels that are equal distance from the center line on the edge side and both terminate at the top of the spine, then your angle will be the same on both sides.

Scribe a line 1/64th on either side of the center of the edge of the steel. This will leave you with around 1/32 thickness at the edge when you're done grinding. Next, knock a 45 degree bevel on the either edge of the blade like this:

Next, walk that bevel up towads the spine. Keep grinding until your edge side of the bevel meets your scribed lines and the top of the bevel meets the spine.

It takes practice to make it all end correctly, and you have to learn how to apply pressure to make the grind do what you want it to. That's why most of us start out as newbies instead of experts. It just takes time and practice to get it right.

--nathan