Machining serrations on blade

[jta69]

I'm currently working on a design for a dive knife - I've never attempted to put serrations on a blade myself, but I get the general idea. I have access to a mill, basically I'm curious to know if anyone has any input on what bit sizes/angles I should be using etc. I'd like to mill the serration from both sides of the blade.

Here's 2 basic part drawings of what I'm making(minus the serration):

Haven't decided between partial serration or putting about 3.25" of serration on the spine of the blade.

 

[Paul Savage]

I do mine on a surface grinder with a 1/8" wide wheel dressed wih a 1/16" radius . I have an angled fixture that I clamp the blade into while I perform that operation. I find using a mill is more work but it can be done by roughing in the serrations with an endmill and then putting in a dremel mounted point 1/8" diameter stone in place of the cutter and run the mill on high speed to clean up the endmill marks. This provides a nice sharp edge.

 

[Overmountain]

+1 on grinder. Serrations work fine and are easier to sharpen if only on one side IMHO. Nix the serrations on the spine. They would turn out more like saw blade teeth and be an injury waiting to happen, especially under water.

 

[Sandow]

I've only played with them on the mill. Instinct was a 1/4" ball nosed mill since it would be easy to sharpen. The serrated knives I've had to sharpen would make me agree with just doing them on one side. Bad enough to deal with even then.

If you are milling the flats, you can just use the same angle and take it down to whatever depth seems appropriate. Would make sharpening fairly painless that way.

Few things struck me based on the diving I've done. The grip needs to be tolerant of a user wearing gloves. Seems a little tall for neoprene gloves unless you have truckasaurus hands. Worth putting a lanyard hole on it; chasing it down into the drink isn't really an option. I've always liked the tip to be capable of prying and the butt good for banging on my tank but that is a preference thing more than anything.

-Sandow

 

[jta69]

I've only played with them on the mill. Instinct was a 1/4" ball nosed mill since it would be easy to sharpen. The serrated knives I've had to sharpen would make me agree with just doing them on one side. Bad enough to deal with even then.

If you are milling the flats, you can just use the same angle and take it down to whatever depth seems appropriate. Would make sharpening fairly painless that way.

Few things struck me based on the diving I've done. The grip needs to be tolerant of a user wearing gloves. Seems a little tall for neoprene gloves unless you have truckasaurus hands. Worth putting a lanyard hole on it; chasing it down into the drink isn't really an option. I've always liked the tip to be capable of prying and the butt good for banging on my tank but that is a preference thing more than anything.

-Sandow

Yeah thanks for the advice - this is very much still a work in progress. Those two holes are for a lanyard and this is just a one-off knife so I designed the handle to fit my hands specifically, I have really long fingers and most handles feel too small. Also living in Florida I've only had to wear gloves once in the past 10 years so as far as I'm concerned they're not a factor.

 

[Sandow]

Makes sense then. Some of the diving I've done in the Med. and west coast has been on the cold side. I hear the galapagos can get miserable cold too.

Out of curiosity, what steel and handle material were you thinking of?

-Sandow

 

[jta69]

Makes sense then. Some of the diving I've done in the Med. and west coast has been on the cold side. I hear the galapagos can get miserable cold too.

Out of curiosity, what steel and handle material were you thinking of?

-Sandow

For steel I'm leaning towards N680 or X15-TN. Admittedly, this is the first blade I've made where corrosion is even a remote consideration I don't have a ton of knowledge regarding their material properties. As far as handle material goes I'm kind of at a loss - I want something that has a good grip but I'm guessing any rubber-like polymer is probably out of my manufacturing capabilities. Honestly I may just wrap it with paracord like a Strider I've had good luck with that before and it looks cool so there's that too.

 

[Sandow]

Did a quick example in soft wood. 3 sets 5 serrations with .180, .240 and .300" spacing. You could do the serrations on both sides if you want but they will be twice as deep relative to the blade edge. If you want a more elliptical serration you will need to mill them at a different angle than the bevel.

http://www.flickr.com/photos/98126710@N08/9320616401/in/photostream/

Might think about nylon for the handle. Easy to mill and sea water won't do anything to it.

-Sandow

 

[jta69]

Did a quick example in soft wood. 3 sets 5 serrations with .180, .240 and .300" spacing. You could do the serrations on both sides if you want but they will be twice as deep relative to the blade edge. If you want a more elliptical serration you will need to mill them at a different angle than the bevel.

http://www.flickr.com/photos/98126710@N08/9320616401/in/photostream/

Might think about nylon for the handle. Easy to mill and sea water won't do anything to it.

-Sandow

Awesome thanks man I don't know why I didn't think about that - I should probably play around with wood until I get it right. Yeah nylon would be great I recon I'd probably have to cut a pattern in it or it would be too slippery underwater.