Large Chopper Advice / finished, photos added

Richard338

Richard338

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May 3, 2005
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I'm making a large chopper and have roughed out a profile but could use some advice on a few points.
(This project is my apology to my grinder for recently making small cheese knives...).

I started with a piece of CPM 3V, 18" x 2" x 3/16".
I want to hack bushes and small tree limbs in the yard etc. The blade will be about 13".
I was reading threads about competition choppers and thinking about the handle construction and the grind.
Suggestions appreciated on the following.
1) The grind: Many competition choppers seem to be full flat grind, but they are thicker than 3/16". I'm thinking to start with a flat grind, but then convex it to keep a bit more behind the edge.
2) People recommend stall mat rubber for the handle slabs on a full tang. I actually have some pieces of stall mat, but they are 5/8" thick. Do people fasten them at that thickness and then shape from there? or thin them to start with?
3) Any suggestions about lanyard hole placement? Would these be advisable even just for backyard use?
4) Heat treat: I'm thinking to send it to Peters specifying 60, but I have read about competition choppers at 63.
Thanks!
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Put the lanyard hole at the front of the handle. You aren't making a competition chopper... go with Rc 60-61.
Convex grind will be tougher in rough use.
Install the matting and grind to shape for an ergonomic handle.
 
I built my chopper with 5/8" stall mat. I didn't take any width off the center areas, so i'd say it's the minimum thickness to start. Gorrilla glue super glue is the best thing for adhering these (epoxy won't work well) I also used corby bolts. I also plan on wrapping the handle with hockey tape, to improve grip and to add a little to the strength of the scale/ tang bond. This material DOES absorb impacts, which is the main reason for it's use in competition.

I have seen at least at least one competition chopper with a "semiconvex" edge. That's how Scott Gossman does it. Having seen it in action, it is most impressive.

Here are videos of his grinding technique and one of his choppers in action. I guarantee this thing will still shave hair after this:


 
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And you even left a little hump on the top for your lanyard hole. Just round off the corners, drill a 3/16-1/4 hole, chamfer. and you will be good to go. I lost the pics of bigger choppers that I have done like this, but here is an example on a fighter. IMG_0095.jpg
 
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Thanks everyone for all the input.
Fantastic videos. His procedure is roughly what I was visualizing, but it was great to hear it clearly explained.
I'm going to try the grind this weekend.
 
You also got to hear a great example of a Baltimore accent. Scott's a really great guy and he knows hard use knives.
 
I also just looked closely at the photos that Matthew Gregory posted for the recent event at Peter's. I could get a pretty good idea about the handle construction and lanyard.
 
I don't post often but since my name was brought into the discussion, I'll comment about my grinds. Thanks Kevin. BTW, Dwayne and I are still working on getting certified to be trainers for Bladesports.
Richard338, my grinds are 75% flat and 25% convex as explained in the video. My edges vary depending on the knife and it's use. Most if not all CPM steels I work with are now getting a near zero edge on them. My competition knife pictured below is made with CPM 4V with a zero convex edge right at 0.10 thick. Hardness is 63 rc.
I would suggest you going with Brad at Peters heat treating recommendation for 3V. He knows his stuff. I run my 3V at 59/60 rc.
The flat grind has always been the grind of choice with Bladesports although more convex grinds are finding their way to comp knives. Donavon Phillips has been making his comp knives as of late with a convex grind. I showed him my method back in March when I had a competition at my shop.
As has been said, forward lanyard is highly recommended. I put them on all my large knives. The handle on my comp knife has 1/8" thick micarta liners, horse stall mat with a coating of truck bed liner. This combo makes for a very secure grip and absorbs a lot of vibration and shock.
Scott

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Scott, thanks for taking the time, lots of great info.
Now I'll take a crack at it and see what I come up with.

edit to add:
I did the grind this afternoon, only took about 90 minutes mostly with a 36 belt.
I modestly claim I nailed it.
I indexed two lines 0.05 apart along the blade edge and a center line as well.
I got the flat nicely from the spine leaving the 0.05, then convexed the rest.
I left it at around 0.025 and can't wait to get it back from heat treat.
 
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KING SOLOMON is born!!!

I got it back from heat treat last week and finished it today.
The grind came out nicely, with an even convex all the way along the 13" edge.

As per Scott's advice, the handle is 1/8" micarta liners with Corbys and then stall mat rubber on top (gorilla glue super glue).
Thanks to everyone for their pointers. I got some truck bed liner but didn't apply it yet. The stall mat is already very grippy even wet.

The baby carrots didn't stand a chance.
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What hardness did you go with from peters?
I use 3V quite a bit, for big choppers and machetes i go for thhe max toughness HT.
Which comes out to 59-60HRC.
The other heat treat you could try is the delta protcol 61HRC. Improved edge holding, and corrosion reisistance (think stainless).
Good choice starting with 3V you can really push that steel hard and go thin behind the edge.
Those poor carrots didnt know what was coming.
Post use pics and use vids if you can!
 
...where are you guys getting the ‘delta’ 3v Heat Treat protocol? It’s a proprietary process, with only three folks that I’m aware of that have rights to it...
 
I called Brad from Peters this time and went with his recommendation of hardness at 60 with cryo treatment.
(the test points on the work order said it did come out it 60)

I sent it off to have a sheath made, so I can't chop anything right now...
 
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