Full convex questions.

dresnor

dresnor

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Feb 1, 2011
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I am getting ready to make my first knife out of 5/32 O1. I want to make as near a full height convex as I can. I don't mind a little flat section at near the spine if it means saving the blade height.

I currently have a 1 x 30 belt sander. I plan on making a jig out of some angle iron to help keep things even.

How do you go about making a full height convex?

Do I need to remove the platen to help achieve the convex?

How can I ensure that both sides are evenly matched?

Any help is greatly appreciated.

Here is a rough drawing of what the blade shape will be.

14275688837_f8a20a3407_z.jpg


Jeremy
 
Suggestion #1 - I would use thinner steel. 1/8" would be my max on a knife like that. .09-.10 would be even better. However, if you want a heavy and thick blade with a convex grind for bushcraft, be prepared to do a lot of filing/grinding/sanding.
Suggestion #2 - A jig won't make a convex grind.
Suggestion #3 - While the basic shape is OK. I would suggest you shape that knife a bit more. Look at some of the knives in The gallery and online and see how blocky your looks compared to them. We often call the shape you have a "Bar of steel" shaped knife :) . It is a common first knife shape due to trying to make the knife fit as much of the the bar of steel as possible. Waste some steel and make a shapelier knife.
First thing would be to add a small curve to the spine line from butt to tip. Unless you plan on doing a lot of batonning, I would curve the edge of the blade from tip to the flat part of the edge a bit more smoothly.
I would also raise the tip up a bit. 1/8 to 1/4" will make a lot of change from the "Spear" look it has now.
 
I agree, the blade shape is blocky. I do plan on making a small curve like you said on both the spine and the edge. I plan on doing light batonning with this knife but it will mostly be a bushcraft, camp knife.

I understand that the jig will not create the convex. I planned on using it to help me keep things even.

Thanks for the quick reply and critique.

Jeremy
 
The only way to get a good convex is free handing. You cannot accomplish this well with a 1x30 grinder imo. There is not enough tension on the belt, and the tracking is no good. To do a full height convex, removing all that metal against a slack belt is not a fun thing for me to contemplate. If you insist though (nobody could have stopped me from making that first file knife), use sharp belts, and do most of the hogging off on the flat platen, then remove the platen and convex at the end. Or!!!!! What you can do with your setup is make a line maybe 1/2 or 3/4" up the spine, and do a 'convex scandi'. The resulting knife is quick to make and fun to chop with. (If you leave the forge scale on there, you never have to finish a flat, and the knife will take maybe 3 or 4 hours to make.)
 
I have made quiet a few convex knives on the grizzly 1x30 and all I did was take the clear plastic guard off and there is a slack belt section about 2"+ and I used that. I think if you took the platen off it would be more slack than you want..... were you going for any paticuler design when you designed this? the woodlore knife is a pretty good bushcraft design you could just make it a convex grind.
 
I agree: Waste more steel. I made a quick photoshop of what is meant. It is not a template only a suggestion. More curves means a design wise better "flowing" knife lines.

Maybe you could make 3 or 4 small flat grinds with your jig at various angles and then "round them off" on your sander or per hand? From the cutting edge, make a 1/2 inch high bevel at 10°. Lower the angle to 8° and add the next bevel. It will cut up and down, lowering your 1/2 inch to 1/4th) Lower to 6° and so on.
Then round the entire thing off with sandpaper on a 1/8th rubber backed block?

Handle: Make sure you don't put a square slab of wood on your knife. Round it from to back and top to bottom. I added something of a taper down to your ricasso that you could easily do with a half round file.


Again, only a quick suggestion. Many lines can be optimized. The thingy at the front of the handle can be shorter for instance. Other blade shapes are possible. You can make the grind line meet the line of the "thingy" for more style.
x4ismd.jpg
 
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Thanks for the advice guys!

I went back to the drawing board. Even though this needs more work I am much happier with the overall look and I believe it will translate to a better working knife as well. Flat handles? No way. I love my Helle, BHK, and TM Hunt knives with nice handle curves.
The pin placement was just a thought not set in stone.

14322667868_c3fff4b940_z.jpg



Jeremy
 
See now that is 20 times more elegant and probably WILL work better as well. Have fun and keep us updated!
 
Greatly improved. See how much a tiny curve adds! The total loss of metal is probably less than 2-3%...but what a change.

I would think long and hard on that pin placement before drilling any holes.
Food for thought:
What will happen to the two front pins when you shape the handle? ( they may become oval/pear shaped and end up on the curved portion of the handle.)
Would putting the "middle" pin in the middle look better?
Would the middle pin look better if it was larger than the front two pins? ( smaller front pins will take care of question #1. Half the size of the middle will work.)
The rear thong tube looks fine, but might move inward a tad. (It will look balanced if made equal in size to the middle pin.)
 
Thanks guys!

Like I said, the pin placement was just a thought. I am not even sure if I want to pin the handle on at all. I may use bolts. Either way the middle pin or bolt will be in the middle of the handle. Thanks for the tip on moving the thong tube inward.

The size of the O1 bar I have is just barley tall enough for this knife. I think I am going to save this piece of O1 and get something taller so I can make sure I get the blade shape I want and may bump up to 3/16 since this will be a camp knife.

Once again, thanks for making me look at this project differently.

Jeremy
 
Getting closer now I see. Have you started the steel work yet?
 
Don't buy thicker steel. Buy thinner steel. Make it cut like a knife should. Thin is in.

And, no offense guys, but the blade shape he drew originally was almost exactly a Kephart style. The handle was off and needed fixed, but I disagree with changing the blade shape. EV13WT, the knife you drew over the top of his drawing is a totally different style of knife. I think it's a nice knife that you drew, but it is a totally different knife.
 
medicevans said:
Don't buy thicker steel. Buy thinner steel. Make it cut like a knife should. Thin is in.

And, no offense guys, but the blade shape he drew originally was almost exactly a Kephart style. The handle was off and needed fixed, but I disagree with changing the blade shape. EV13WT, the knife you drew over the top of his drawing is a totally different style of knife. I think it's a nice knife that you drew, but it is a totally different knife.
Click to expand...


True. I meant to edit in a disclaimer that my pic changes the style of the knife entirely, but I forgot. Off to google Kephart. :D

Ben
 
Lol. I was hoping you wouldn't take that wrong. I didn't mean it snidely. Just factually.

Look up ML Knives while you're at it. Matt's customers say his handles are some of the most comfortable they own.
 
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