Thread: Help with a grind issue

Wow guys! Seven replies in two hours! Quality stuff gentlemen, quality.
Charlie, thanks for letting me know that is normal.
Max, I am indeed making this all by hand. I'm in negotiations with the CEO to buy a 2x42 grinder from Craftsman. Barring that, a 1x30 from Harbor Freight. I am also interested in knives, but I need to get this thing done first and really understand what's happening and why.
Ray, thanks for making the wedge for me. That really, really helps me understand what's happening with the geometry.

I understand now why filing to the middle and then flattening on the plate then filing to the middle and flattening to the plate has me chasing my tail. I can't wait to get back into the shop tonight and try this out!

Any suggestions on finding the center on such a thin, uneven edge? I know, I should have done the center marking on the original blank, but that ship has kind of sailed. Next time I'll do it correctly.

Lay the blade on a flat surface and use a drill bit that is the same diameter to make the scribe line, If it is 1/4 stock use the tip of a 1/4 drill bit to scribe the line. it is not a perfect way but it is good enough for now. Use a sharpie or something to coat the edge before scribing the line.

Charlie

I can try to do that, but I'm not sure how it's going to work on the thin edge. Maybe clamp the piece so the spine is flat and the edge is "suspended" then roll the drill bit? I have a nagging suspicion that my grind may end up being a little off left to right and I may have to improvise a bit.

Is your spine the same thickness all the way across at this point?

If so what I would do is clamp this to your marble surface in such a way that your spine touches all the way across. Hopefully, the flat of your shank will touch too. Clamped like this your edge should be suspended.

Then as Spazola said take a scribe of some kind the same thickness (Drill bit should work fine) as your spine and make the mark along the edge.

If your spine is not parallel or is drifting to one side due to the struggle you were having you may have to just clamp on the shank flats and use that as a reference to realign the rest of the blade. Keep in mind that if you have to re-true your spine (ie making it thinner by straightening it out) you may have to take a little off the edge to keep the proper edge angle range.

Ray

Thanks to everyone for incredibly useful posts.

No kidding, right!? I'm learning a lot, which is why I hang out here!

To answer a previous question, I am planning on leaving it a true wedge. No way to hollow it right now.

The tang is no longer flat. However, the spine is the same thickness all the way across, so if I can clamp it right, I think I'll be able to get the edge up where it needs to be. I'm hoping I haven't screwed the edge up so badly that it isn't mostly straight.

You can probably clamp on the spine but you may need to shim under the bottom bevel to orient everything and keep it solid so it doesn't move while you are marking. Since you no longer have an established "reference flat" you may have to do a little "eyeballing" while shimming it up but if you take your time I'm sure you can get it as close as it needs to be.

Ray

Also, let me make sure I have this right; filing should be perpendicular to the spine at all times.

Not really. You can draw file this. actually it would probably be easier to draw file this.

The point I was trying to make is that if you have all the geometry in order you should be able to take a straight edge and set it anywhere along the spine (perpendicular to it) and the straight edge will touch all the way down from spine to edge. In other words you won't have any spots where your straight edge gets high centered and rocks back and forth when its perpendicular to the spine at any given point.

It would help to keep a bottle of dyekem with you when doing this to re-blue the blade occasionally so you can easily see any high spots as you file.

Ray
Ray

****Update****

I went out and tried to mark the center. It didn't really work, as it was already so thin as to be impossible to get something to mark it reliably.

I think I have it right. The edge is much thinner, and is the same width across what I would consider to be the "cutting edge." I have a few high spots to draw file out, then I'm going to hand sand it up to 800 grit before I send it off for HT.

For next time, I am going to make sure I make the center before I do ANYTHING!

This thing may end up as a "razor shaped object" and nothing more, but it has been a hell of a learning experience.