Grinding forged blades

[BigBearForge]

Morning Gentlemen and ladies,

I seem to be having some difficulty when grinding large forged blades. I've forged the heel and bevels, keeping everything nice and straight. My edge is now sitting at about 2mm thick. It's almost impossible to scribe a Centre line at this stage. It takes quite a long time to do a primary grind to get my edge down to about 1mm while keeping the edge 100% straight. It's a question of a quick grind and a quick look down the edge. Very time consuming.

Does anyone have some advice for me on how to keep the edge perfectly straight on a forged blade (full tang with a forged finger well/guard) .

 

[weo]

This question would probably get more responses if in Shop Talk (perhaps you could ask the moderators to move it), but I'll offer my thoughts.
Scribing the centerline earlier in your process might help. Forge --> grind the flats --> scribe your lines --> finish grinding.
But, you might also be a bit impatient. I've ground a number of blades without scribing lines, and it is very much a grind/look/grind/look/repeat process. But even with the lines scribed, towards the end of the process, this back and forth is still necessary (at least for me). Scribing the lines only makes the initial grinding a lot quicker because it's easier to see where you need to remove material.

 

[Alex Topfer]

What angle are you grinding the initial bevel to set the edge at?
I usually do an ~45 degree angle to set where i want the edge, then go back later to make it shallower

 

[weo]

I usually do an ~45 degree angle

That's about what I do too, but I've never measured it, so it might be 30-35...maybe I should start using my 45 degree platen attachment that I use for rough shaping my handles...

 

[tkroenlein]

I think there is not an easy answer to your question. Forged blades are never 100% straight, even, centered. At some point, craftsmanship comes into play.

 

[Alex Topfer]

That's about what I do too, but I've never measured it, so it might be 30-35...maybe I should start using my 45 degree platen attachment that I use for rough shaping my handles...

eh, it's just a rough initial step. provided the edge gets where you want it doesn't matter how precise the initial bevel is

 

[i4Marc]

I would suggest that grinding the bevels should not be your first concern. IMHO, you should grind the flats of your ricasso first, making sure they are parallel. Then, using the flats of your ricasso as reference, scribe a centerline through your blade edge. After that the initial bevel will just reference the centerline and be fairly easy to judge straightness and thickness. There is obviously a bit more to it but I would start with your ricasso which is your foundation.

 

[Stacy E. Apelt - Bladesmith]

I agree with i4Marc. Here is how I would deal with it if I bothered ( I do it by eye):
Straighten the blade and edge in final forging as much as you can by eye.
Clean up the blade on the grinder enough to have a flat edge and the bevels ground enough to take out the deeper divots.
Grind the ricasso and tang (or just the tang if the blade has no ricasso) flat and parallel. Make sure the blade is not thicker than the ricasso and tang
Set blade on a granite surface plate or other dead flat surface and clamp the ricasso/tang down.
Use a drill bit that is of a diameter that places the tip just about centered on the ricasso/tang. Hold the bit against the surface plate and slide down the edge scribing a line.
After the edge is marked, flip the blade over and mark again from the other side of the ricasso/tang. This should give you two parallel lines down the center of the blade. Use these to grind your bevels straight and true.
TIP - take some assorted size old dull drill bits between 1/16" and 3/16" and grind both ends to sharp points. Once roughly ground to a point, chuck in a drill and grind against a running wheel or belt to get the point perfectly centered. Use these double ended scribes to mark the center on blades. Store them in a pill bottle labeled SCRIBES.