Re-making the tip on an old USMC knife.

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duxbellorum

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Nov 2, 2014
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I have been working to clean up an old USMC knife from my grandfather that had been pretty heavily abused (used to split wood and do household work). I have done a lot of work to remove the deep scratches and pits present on the secondary bevel and the edge:

IMG_3398.jpg


As far as I know the knife does not have any value as an antique, and at any rate, it has significant sentimental value as a functional tool, so I don't mind adjusting the geometry.

I spent a few hours over the weekend working on the secondary bevel, and the edge, evening out the shape and grind to reach the appearance in the photo (the scratch pattern on the edge and the secondary bevel is from my 2k aota stone), however there is still one major issue with the knife: the point.

IMG_3379.jpg


I think the knife got thrown into dirt and rocks a few too many times, resulting in the blunt tip in the photo.

I am looking for advice about how to rebuild the point in the most natural way. I will be doing this the old fashioned way with my trusty file and my lowest grit stones, and I want to know whether to focus on taking metal off of the spine, the secondary bevel, the edge, and or that funny rear bevel on either side of the spine. (for reference, the spine is about two millimeters wide along the section with that rear bevel, while the whole blade is about 3mm thick with a VERY slight taper towards the tip).

I will be happy to post additional pictures when I have time, if anyone wants to see a different angle (and doesn't think I'm a fool for trying to do this.).

Thanks!
 
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You can sharpen like you would the rest of the bevel until the tip comes to a nice point.
Or you can grind down the spine to meet the tip, up to you.

What I would recommend is to shape it in a way that leaves you the most thickness. 3mm overall is pretty thin.

Also you're pictures died, or something. Could you respost?
 
n7titan, hopefully that fixed the pictures.

The process that preserves the most thickness is definitely grinding the spine, but I think that would involve removing a huge amount of metal.

I am starting to see the following plan to avoid that: To work on the secondary bevel until the primary bevel can hit the tip with the same width as on the rest of the blade.

My guess is that tip is meant to form just in front of the diagonal peak where the rear bevel and the secondary bevel meet. I can adjust the depth of the rear bevel to control how thick the primary bevel will be at the tip and then use that intersection between the rear and secondary bevels to tell me how far to go on the secondary bevel. I will set the primary bevel last, so assuming I have done everything else consistently, the resulting primary bevel should be of even width.
 
The simplest way I can see is just to sharpen the tip normally until you get a tip. There's still a fair amount of material there. Something like this.
IMG_3379.jpg


You will probably end up with a less steep angle but it will be functional all the same and doesn't remove too much metal.
 
^ That picture shows almost exactly how I'd do it. Depending upon the overall geometry of the blade, you might also want to grind the spine a little to bring the tip more forward. I'd only do that part if the new point you are grinding in will be pointing too far back towards the spine. You want the point to aim straight forward in most cases; the combination of edge grinding and spine grinding can adjust the exact direction that the tip aims.

I would definitely start like n7titan shows above.

Good luck!

Brian.
 
anyone close by make knives? I would do it for you if we were close enough together. a belt grinder used for knifemaking would do a fine job quickly and you would get a new bevel to boot.dont know at the number of knives I have sharpened for my customers here. if they buy a knife from me I sharpen whatever they bring that needs sharpened as well as regrind any I made.
 
So I finally took some time to do what I was thinking about on my 300 grit stone. I really liked this approach, because it keeps the tip a bit thicker. If the rear bevel were not as low as it is, the secondary bevel, which actually leads to the tip, would need to be a LOT bigger, thus thinning the entire blade a lot near the tip.

I will be doing some more refinement of the geometry with my 1000 grit stone as I move up through my stones towards polishing. I am thinking about ditching the original primary/secondary bevel and switching to a fully convex blade surface.

What do you think?

IMG_3463.jpg


IMG_3466.jpg


IMG_3472.jpg
 
Looks great.

Maybe some buffing or Scotchbrite pads to uniform the appearance?

Other than that(which is entirely a matter of aesthetic preferences) it seems to be a very quality job. Enjoy it in good health!

Best Regards,

STeven Garsson
 
Man that looks great - I imagine it will look even better when all the surface is uniform.

What was your trick to not "flattening" the tip as you took metal off? Every time I try reworking a tip it seems I need to drop the spine quite a bit to form a nice pointy triangular tip, but it looks like you didn't have to take much off the spine at all.

Cool project, I'm looking to seeing more pics!
 
Some usual polishing stones later (2k aota, 5k suhiro rika, 15k shapton (cuts fast enough I feel justified in making the jump) ) :

IMG_3483.jpg

IMG_3486.jpg


The next step will be stropping, but since I am out of compound, that may be a while. Unfortunately, the Shapton leaves a very faceted surface because it is still so aggressive for a high grit stone. The faceting is completely cosmetic, though, water will still bead on the bevel and it is nicely reflective.
 
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