3d machining a fixed blade?

dylan_d

dylan_d

Joined
Dec 30, 2002
Messages
1,242
Disclaimer: I have never made a knife but I do have 15 years CAD/CAM and machining experience.

I would really like to machine a fixed blade, something like a small boot knife or dagger. I'm not yet sure if I would do an integral or just make it out of flat stock and bolt on some scales but I would like to 3d machine the primary form of the blade.

Who's done this? My main concern is securing the pointy end of the knife. Obviously the handle can have holes for fixturing that will can be later covered but not the blade. How did you get around this? I have some ideas but I'd like to hear from someone who has done it.

Also, I have plenty of experience hard milling, would machining this out of heat treated stock be better than heat treat after machining?
 
Sure, it is done all the time. Most folks do 95% of the work in annealed steel, HT, and then finish, but it can be done from hard stock.
Some folks leave a small round nib on the end and grind it away after HT.
 
This is how I do it. Hold it in the vise to drill the holes, then screw it to the fixture. Machine the top side, flip it using pins to locate. Then machine the bottom side the same way. Finally machine the perimeter to break it away from the stock.
I haven’t had any problems with the tip with this method. I do have to do some hand sanding to get out machining marks/scallops from the bevel.
51DB1C30-D6CF-49AF-9F21-B284E0FE91C4.jpeg

I tried doing it more the way Gough does it. I found that I didn’t get as much support for bevel machining. You’d have to be very precise in fixturing and Machining the perimeter of the edge to get good contact and pressure for support along the edge.
 
TILLER said:
This is how I do it. Hold it in the vise to drill the holes, then screw it to the fixture. Machine the top side, flip it using pins to locate. Then machine the bottom side the same way. Finally machine the perimeter to break it away from the stock.
I haven’t had any problems with the tip with this method. I do have to do some hand sanding to get out machining marks/scallops from the bevel.
View attachment 1434247

I tried doing it more the way Gough does it. I found that I didn’t get as much support for bevel machining. You’d have to be very precise in fixturing and Machining the perimeter of the edge to get good contact and pressure for support along the edge.
Click to expand...

Thanks you, that is very helpful. So when doing the bevel, are you able to run your ball endmill all the way to the edge of the bevel? I would think on the second side that it would break through the support material, is that not the case or do you stay just off the outer edge? Finally, when you do the perimeter, are you bolting the handle down and leaving the blade unsupported? I imagine a little chatter around the blade perimeter at that point is fine since it is not the final shape.
 
I use a 1/4” .09 bull nose end mill or a 3/16 regular end mill. I do a parallel tool path from the edge up. The support material is .015, the thickness I’m shooting for the edge thickness. I may drop that down a thousandth for clearance, but with the bottom depth for the parallel tool path set at the top of the edge, if that makes sense. Haven’t had any issues with going through the support, as long as I set everything up correctly.
 
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