First I scan the drawing and bring it into Fusion 360 so I can trace it
the outline is traced using the curves tool to get it as smooth as possible
once the outline is completed I turn it into a 3D object using the extrude tool
and then add corner fillets and other small details as needed.
Next it's time to create the bevel! I do this by creating an angled sketch which is swept along the blade's edge.
Then I create the plunge line the same way, by creating a curved sketch and sweeping it along the
end of the bevel cut.
With the bevel completed I can easily add it to the other side of the blade by creating a
mirrored feature, this duplicates the bevel and plunge line cuts onto the
opposite side of the knife.
Now I want to add a lanyard slot on the butt of the knife. To do this I create a rectangular sketch, and then use it to cut a hole through the blade
I then fillet the corners of the lanyard hole to smooth them out
The handle would be quite uncomfortable as it is, so it's time to add some chamfers!
This is fairly easy I just need to select the edges I want to chamfer and then
set the chamfer size
The handle is still pretty boring at the moment. But looking at the lanyard slot I thought
it might look intersting as a repeating pattern! This will remove weight and add
grip at the same time!
Looking pretty sweet!
Before I can start making the knife on the CNC I need to setup some tools! Here I'm loading a small endmill into a toolholder that will mount in the CNC.
Now I need to enter the tools into the tool library so I can correctly use them when programming the various toolpaths for making the knife!
I then enter the size of the stock material I'll be using, with that done I'm good to start making tool paths!
First I program the slotting operations for the holes in the handle using a tiny 2mm endmill...
then I program chamfers around the tops of the holes to clean them up and remove any sharp edges!
Looking at the knife while working on it I realized the handle still doesn't look grippy enough, so I go back to the model to add some jimping to both the spine and the finger choil.
Finally I can create the toolpaths for machining the chamfers and bevels and for cutting out
the knife! Somehow I forgot to film the creation of the bevel toolpaths,
I must be getting forgetful in my old age!
Now that all the programming is done I can begin setting up the CNC! First I measure the X and Y location of the stock using my 3D taster and a parallel that's the right size.
The 3D taster is a really awesome tool. It's basically a dial indicator that can read in all three directions, it makes setups very fast!
I then measure the Z location of the stock. In this case it's a
piece of A2 tool steel that I've already heat-treated to 62.5 Rockwell C. I did mention I was
going to hard-mill this knife right??
Hard-milling is the process of machining steel after it's already been hardened. This is a
technique that requires careful setup, but can deliver better surface finishes and tighter
tolerances than what is possible when machining steel before heat-treatment.
Now the stock position has been measured I need to measure the tools themselves! To do this I use a sweet little conductive touch probe. This thing was cheap but works really well!
Finally I've got everything setup and I can begin machining the knife! First I'm going to
machine the slots all the way through the handle, using a tiny 2mm endmill that I rescued
from my scrap bin... I wouldn't use a junker tool like this on a customer's knife but
for this project it will work just fine!
You can see the dull tool has left some serious burrs on these slots! That's fine though because next I'm
going to chamfer the tops of all the slots using a 45 degree solid carbide chamfer mill!
That has come out looking really clean!
Next I need to cut the outline of the knife half-way through the stock so I have the access I
need to cut the chamfers and so on around the handle! You can see this is going to be a pretty
slow operation with that tiny 2mm endmill. That's fine though because the CNC can finish
this while I work on other things...
With the outline completed next I want to use a helical boring toolpath to cut the jimping holes
all the way through the stock, this will ensure the jimping lines up perfectly on both sides of the knife!
Then I cut the chamfers at the top and bottom of the handle, again using a 45 degree solid carbide chamfer mill.
With all that done I'm finally ready to tackle the trickiest part! Milling the bevel into the blade!
Doing this on hardened steel is a challenge because the tool can heat up quickly, so it is cooled
with a high pressure air blast. The hard steel can also chip the tool quickly if I'm not careful to
take small consistent cuts.
To reduce the load on the tool the bevel is machined in three stages, 2 roughing passes and
then a final finishing pass. The finishing pass is only removing a couple of thousandths of
and inch of material, this is to make sure I don't chip the tool and ruin the finish!
Separate tools are used for the roughing and finishing passes to make sure the finishing tool
does not get worn too quickly. After the finishing tool is used up it becomes the roughing tool
and a new endmill is used for finishing!
The extra care needed is worth it though... have a look at that awesome finish on the bevel!
With the first side completed it's time to flip the blade over and start machining the other side!
Here you can see what happens when heat is allowed to build up in the tool too much, within
an instant it's glowing red hot! Most of the heat is kept at bay by the fancy coating on the tool
so it's fine after it cools down, however if I was making more of this knife I would definitely
change the toolpath to avoid that issue as I don't want to overheat the steel.
Machining the second side of the blade is pretty much the same as machining the first side, so I'll show it a bit more quickly...
The final tricky machining step is to finish cutting out the blade... To do this without allowing
the blade to move I am leaving tiny tabs around the edge to hold it in place. The tabs are only
10 thousandths of an inch thick, so they can easily be broken by hand later.
That is really satisfying! You can see the tiny tabs along the edges that held the blade in place.
The tabs are ground off flush using a 120 grit belt on the belt grinder
Then the profile of the knife is cleaned up using a 600 grit belt
The flats of the handle and blade are then finished to 600 grit by lapping them on a granite plate topped with sandpaper
Now it's time to hand-finish the bevels! To do this I use mold polishing stones... These are
kind of like sharpening stones, but they're made for finish sanding. They were originally designed
for use on large injection molds, and they make hand finishing much quicker than if I were to
use sandpaper exclusively...
As I use the stone it wears to expose fresh abrasive, which means it's always cutting very aggresively, hence why it's so much faster than sandpaper!
Sandpaper still has it's place though! I use sandpaper sheets to do the final push/pull strokes
which produce the clean satin finish. The stones cut quickly but tend to leave inconsistent
grit marks.
The hand finishing is now done, and it's time to move on to sharpening! The sharpening system
I'm using is one I designed specifically for my knives. I rough in the edge with an 800 grit CBN
wheel, and then finish the edge on an MDF strop loaded with 1000 grit CBN paste.
This allows me to quickly produce excellent edges, without any risk of overheating the steel.
You can see it's terrifyingly sharp, as always!
Hey Guys! So this was a really fun little project. One of the reasons I wanted to make this knife was actually just to try out the method of CNC machining that I showed in the video
where I machine it from a single block of steel and then use tabs to hold it in place during the final operation.
The main issue with that process is that it doesn't let me have the same level of dimensional tolerance around the outside because I have to leave those tabs and then hand finish them off
Obviously the process for the Resolute is a lot more complicated than what you saw in this video
but I did actually touch on a lot of the different facets of CNC knife making in this video!
I'm going to be making a lot more videos over the next little while so hopefully I'll be seeing you guys again soon!