Custom folding kinfe WIP.


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Thread Index.

I decided to do individual post for each aspect of the knife. It should make it easier to discuss each aspect and keep a good continuity through out the post. I will add links to my posts for people to reference comments that are beneficial and informative.
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Design and theory.

Like everybody I wanted to try and do something new and maybe be a little different. The more I looked the more I realized that it has pretty much all been done. While I am doing something a little different with the ball bearings it is more an ends to a means rather than being an innovation.

My aim is to make full custom folding knives. With so many well established makers in the market place already there was no way (or desire) to try to make it cheaper. I enjoy complexity so I decided to make something that is more complicated as a way to give the customer something that, while not wholly unique, has a demonstrable level of workmanship. There are 16 screws in the knife and you only see the 2 that are in pocket clip. There are also 50 plus holes that were drilled.

As for design I will give some general thoughts for people who are looking for some ways to improve. The knife in this post is not by any means perfect. There are still some lines that don't quite do it for me but I feel that it is close enough and to keep improving it needs to be completed so I may as well share it!

Here are the general principals that I kept in mind.
It needs to be consistent. The flow of the lines and overall shape should have a coherent thought process. The use of color and texture should also highlight the natural lines of the knife. Lastly, the overall finish quality needs to be consistent across the whole knife.

Find as many little things as you can to show that you have put as much effort in designing the knife as you did in making it. I tried to make as many things line up as possible. In this knife the flipper tab lines up with the bolster and finger groove when open. It also does not protrude below the bottom of the bolster when it is open. When the blade is closed the rear of the blade lines up with the end of the bolster. I also decided to try to highlight the different angles and arcs by not rounding them off. I kept the lines as clear as possible. I also did a bevel rather than a radius on the handle to help highlight the lines.

The actual mechanical design is simpler but can be very hard to execute. The relationship between the pivot, stop pin and lock bar are strongest if they form a triangle with equal sides. As you get into designing the knife things have to move to fit for aesthetics but it bears keeping in mind. Part of that is planning out where the lock face is. The relationship between the lock face and the detent ball in the lock bar have a very close relationship. I spent a ridiculous amount of time getting the detent ball to stay on the blade as it rotated.
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Tools and prep.

Bridport style manual mill with a digital readout. The DRO is accurate to .0002
Universal tool post grinder. I made an attachment so use 2X72 belts for surface grinding. I also use it to cut the lock face.
Variable speed belt sander. I made a custom large diameter (22 inch wheel) grinder.
Heat treat oven.
Rc tester.
Home made titanium anodizer.
The mill has a compound rotary table on it. It is a 15 inch rotary table with a built in 10 inch square table on top. It is used for cutting the slot for the pivot pin into the blade.

The various other hand tools and tooling will be mentioned in the individual posts as I use them.

As for prep work, the main thing is to get all the blank metal ready to be worked. I find it to be way more time efficient to do it all at once. Every time you cut or use a sander it creates a burr. Get in the habit of taking the burr off every time you make one. When all the pieces are cut to size it is time to stick them in the oven and get any hard spots out. On one of the titanium bolsters I ran in to a hard spot which ruined a center drill and an hour and a half of time. On the titanium I stick it in the oven at 1000 degrees Fahrenheit and let it slow cool. I spent a fair bit of time researching this without finding out a whole lot of info on it. I would appreciate it if somebody who knows how to do it would chime in!
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The first step is to get it all flat. I am using 2 sided tape by 3M to hold the titanium in place.


Next is getting all the holes drilled. Here you can see that all the holes are center drilled then drilled (2 of them are pin holes which are reamed) and I am starting to chamfer them. It is a little tedious to go back through and chamfer them as a separate operation but I am using the digital readout to get the depth on the Z axis the same across all the holes.


I don't have an existing template but I did make one out of plexi glass to give me a starting point. Looks like it is ready for rough shaping so I can start in on getting the bolsters fit up.

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On the bolsters there are the 3 mounting screw holes. They were center drilled, drilled and taped for 2-56 screws. The hole depth is .085. This is where a tap-o-matic really comes in handy. It is so nice to be able to tap a 2-56 blind hole and not have to worry about anything. Lastly, the screw holes needed to be chamfered slightly to allow proper screw cleareance/depth when mounted to the liners. The liners are thin enough that the 82 degree screws sit just below the liner surface.

Next was milling out the bearing plate pocket. It consisted of drilling a 5/16 hole for the pivot. The large diameter center circle was done with a 5/8 end mill. Next was using a 25/64 end mill for the alignment pin location. And lastly I used a 3/16 end mill to make the tabs for the screw holes. I went .08 deep on all of the cutting actions but it was hard to get all of the separate cuts to be the exact same depth. I need to experiment a bit to try to get it a little cleaner.

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This is the bearing plate. It is the same material as the blade (S30V) and hardened to 60rc. The bearing plate is mounted to the top of the liner. This allows me to do several things. The liner has the bearing pocket in it so by adjusting the thickness of the liner I have a really tight control of the spacing between the handles and the blade. This knife came out to .007 clearance.

By having the bearing plate and blade surfaced ground everything is going to be running very parallel. By clamping directly to bearing plate/bearing/blade and then having the liners bolt to the plate this in theory "may" give me a fuller contact between all the pressure points caused by the clamping of the pivot screws and bearing contact points. I realize on a good mill you could mill the bottom and sink in a bearing pocket then put in a hardened washer. What this avoids is any difference in alignment from minor changes to parallel as you surface grind ether side of the scale.

It also allows for recessed pivot screws.

The bearing plate has 2 mounting holes. Blade pivot hole and the spot pin hole in it.

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The trick here is now do you mount a scale with hidden hardware that can be removed and put back on and maintain alignment. The only thing that I could think of was to have chamfered holes in the liner so that when tightened it "should" return to it's original place. Next is to mill out a pocket in the carbon fiber and make up a metal screw insert. With the inserts screwed down on the liner place a small amount of epoxy in the scale and clamp it down. I used renaissance was to keep the epoxy from sticking to the metal and a blob if it on the screw to aid in removal. After it dried I then back filled the gaps in the epoxy to get full coverage. A note on the clamping. I clamped it with the scales on the bottom so that the epoxy would be sure to make full contact with the insert. This allowed me to use less epoxy and not worry about it squishing out everywhere and making things more difficult.

To match the arch of the bolster to the scale I clamped the bolster down and scribed a line. After you remove the material down to the line you start holding the bolster in place where it will mount and back light it to easily see any gaps. Carbon fiber works pretty quickly so the trick is not to take off too much. I found that having several different sizes of tubes to wrap sand paper on really helped with getting it dialed in. I had dimensions from .5 to 4 inches.

The last note is to get set up in a work position where you can be perpendicular to the work piece.. It is really important to keep everything at 90 degrees. I did fudge a little on the inside edge by removing a few thousandths to create a small unseen bevel to help with any slight gaps that may occur from being slightly off.

I ended up doing a bit more work on the mounting surface to the bolster after I had milled in the pocket for the metal insert. This caused things to move a bit so things are not as clean looking as I would like on the back side of the scale.

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It worked! I had the handle fully disassembled and then cleaned it up a bit and put it back together. This pic is after reassembly. The only thing I don't like is how ugly the back side is. On the next scale I think I will do a plate connecting the two holes which should make it cleaner, stronger, and easier.

OK, Here is the improved design. By having a solid bar it provides more support to the knife as a whole. It also increases the surface area for the epoxy to hold. I also put a bevel on the mounting bar to help give the epoxy better purchase.

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Here is a pic of it all dressed up :D
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The blade pivot has been drilled and reamed. It is undersized as I will ream it for the pivot after heat treating and surface grinding. This ensures that everything will stay in popper alignment in case of some mild warp-age. The pivot stops have also been milled on a compound rotary table. In this pic i am setting my blade tip height, blade width, flipper tab location while open and closed and getting an idea of the lock face position and detent travel path. The bearing plate is not installed on the liner but the pin size is the same in both pieces so that I can have the blade swing up against it's actual stops.

I didn't bother posting a pic but I had to modify the original blade. The original blade had an arch of 178 degrees. I ended up needing it to be 175.5 degrees. An interesting fact. For every degree you change in the pivot slot it moves the hole location by .005 inch for the radius of the circle that I am using.


For the jimping I had to take a gunsmithing checkering file and grind off about 2/3 of it so I could get into the small arch for the flipper tab.

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This grind is what I would call an EDC grind. On the next one I think I want to but in a top swedge to make it look a bit more aggressive.
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Lock face, lock bar, and detent.

To do the lock bar I used a cobalt slitting saw spinning at 60 RPM. I am holding it in a machinist vice and to line it up I just eye balled it.


To do the lock face I made up a jig and mounted it in a machinist vice. This gets me to vertical on the blade in relation to the knife. The jig was made on the mill and I used 01 tool steel that is flat ground. I used a dial indicator and got the jig square on the mill before I center drilled, drilled, then reamed the holes in the jig. The magnetic vice on the tool post grinder is square to the machine so all I had to do was rotate the tool post grinder head 7 degrees. This is a video of me cutting the lock face.

For the Detent ball and detent hole on the blade I also made up a jig. I mounted the liner in the jig and put it in position on the mill and clamped it down. After drilling the liner I put the blade on and used a carbide center drill and drill bit to make the hole. To get more info on it I would recommend Don Robinson's book "My Way".
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Pocket clip.

My main gripe about the pocket clip is that it is positioned incorrectly on the knife. It need to be moved down a bit and the screws need to be in better vertical alignment to allow for a deeper fit in the pocket. As a result of the alignment being off the shape and sharpness of the lines on the pocket clip couldn't be as defined as I would like.

One last thing worth mentioning. The screws for the pocket clip go all the way through to the scales on the other side which have a plate installed with threads in it to hold the rear of the knife together. These are the only visible screws on the knife :D

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I build my own anodizer. All the info is out there online and I don't really feel like much of an authority on it yet so I will not say too much on how to build one here.

The solution is TSP (trisodium phosphate) and I used 25.3 volts to get the color.

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