My Folding Mule Project

[CasperFatone]

I got the pivot hole drilled today, which feels like a big step forward. After some deliberation I decided to just go with a 1/8” hole and forgo a pivot bushing, but I figure I can always enlarge the hole to use one if need be. Hopefully the ceramic is low enough friction that it doesn’t need one, but we will see.

Unfortunately I now have to wait a bit to proceed the way I’d like to. A couple days ago I purchased a used Kizer Drop Bear on Reddit knife swap that comes with extra hardware for the purpose of design study and providing the necessary parts, but it still hasn’t been shipped. I wanted to check out the Drop Bear in particular because Kizer’s version of the cross bar lock has adjustable spring tension which I feel is a nice feature. Hopefully it doesn’t take too long to get here because I’m dying to get to work on this thing!

[Mrchunkle]

I was going to jump on here to laughingly ask you to make a folder out of the ceramic mule. but here I find you already starting. were you thinking of a ceramic ball detent? Any other material would just wear away

[Fireman]

[CasperFatone]

I was going to jump on here to laughingly ask you to make a folder out of the ceramic mule. but here I find you already starting. were you thinking of a ceramic ball detent? Any other material would just wear away

I’m going with an Axis/crossbar style lock, so no detent ball needed on this one

[CasperFatone]

I decided hold off on making my HIC Axis lock Mule, mostly because it seems like a difficult material to learn a new lock with. My thought is to probably make an Axis lock Mule with one of my other Mules first, then fit the HIC blade so it can be swapped in. Also, this whole thing is only about making what I feel like making and right now I want to make something else.

The thing my mind is focused on for some reason is making a lightweight compression lock Mule, so that is what I’m doing. It will be built in a similar fashion to the Para 3 LW, only I am using G10 like the liner less Native 5. The lock bar is going to be .060” titanium and will be held in place by screws from outside the show side and sandwiched between the scale and a backspacer. I’m going to use a shouldered stop pin that can also be screwed in with 2-56 screws, and as with pretty much every folder I do I’ll be doing PB washers and a pivot bushing.

The Mule I’m using as a donor is my other 15v, the first of which became a liner lock flipper. After how nicely the liner lock 15v Mule flips I really started wanting one that flips as well with a comp lock. I figure the worst case scenario is that I adapt the blade into a knife with full Ti liners if my LW idea doesn’t pan out. However I’ve made a liner lock knife with this same style construction and it turned out well.

So far I’ve just laid everything out, cut my G10 scales to shape, and did the lockbar relief in the show scale. I had to do the last little bit of the cut freehand because the template bit has a 3/8” diameter. My pics show the jig that I made to do the relief cut using a top bearing template bit in a trim router. The cut has a slight angle as it gets closer to the blade tang to allow for the bar (plus the detent ball) to move out of the way. This was done by adding a small shim to the template after the initial cut and slightly lowering the bit.

To make the lock bar I am simply using a piece of tape to transfer the shape over to my sheet of titanium. The tape was stuck on the scale and rubbed with a pencil, then stuck to the titanium. I will cut it out close to size on my portaband/table setup and creep up on the fit on my grinder.

Here are some progress pics. Hopefully I can spend some time on it this weekend.

[Bolster]

Very clever jig work.

[CasperFatone]

Very nice

I'd look at some cheap Chinese CNCs - that's what I have but never use for these purposes. It's about 600$ with upgraded motors and software, but totally worth it if you do this stuff a lot which I don't. I started the same way.

Not a bad idea, but I actually enjoy doing this kind of hands on work. If I ever wanted to make these to sell I’d probably get a CNC. However, I have almost zero interest in ever making these to sell. I’m really only doing this for my own enjoyment, to practice making different lock mechanisms, and to make my Mules something that I carry daily.

Very clever jig work.

Thanks, I really enjoy making jigs lol. I’ve been a custom cabinetmaker for 20 years so it comes second nature at this point.

[sal]

Great stuff.

Thanx much for sharing.

sal

[CasperFatone]

Here’s a quick progress update. Things are moving along nicely with this one. Cutting the lockbar was pretty painless, and in this first pic you can see it in place. Also you can see where I drilled into the the tang to mark the center of my stop pin locations at open and closed positions. This was done with a #51 carbide drill bit using the scale as a guide with the blade held in each position.



The next pic is the true moment of no return, aka cutting the blade in half! You can see that I enlarged the stop location holes to 5/32” because that is the diameter of the shouldered pin I’m using. There is also a rough outline of how the tang is going to be cut.



The last two pics have the stop locations set and I have ground the tang to clear the stop pin as it rotates. Usually I would mark the tang for the lock cut using the liner as a marking template but that isn’t possible with this build. Instead I plan to do the lock cut first, then mark and grind the lock bar to fit the tang. Losing some material off of the bottom edge of the lock bar is actually going to help me get more purchase on the tang, plus it will be easy to grind since it’s removable (not to mention replaceable). Hopefully this weekend I will have time to get the lock functioning.

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[CasperFatone]

I ended up making my backspacer out of Cocobolo just because I had some that was close to the correct thickness. The backspacer on this knife is pretty unique in that it isn’t just a spacer, but it also helps to anchor the lock bar. The two pieces are press fit together with two 1/8” 2-56 threaded connectors, which stiffens the whole assembly, and more importantly allowed me to take off the “show” scale and keep the lock bar in place. That made it possible to drill into the tang using the detent ball hole in the bar as a guide, which is how I always drill my tangs for a good detent. Here is a picture of the knife with the show scale removed to drill the aforementioned detent pocket in the tang (pivot screws is going through a temporary spacer to keep the blade/washer stack tight).



This is my first time using a shouldered stop pin and it basically dictates everything when it comes to spacing between the scales (washer/blade stack, pivot bushing, backspacer). It’s kind of a pain in the ***, but hopefully it is worth it. I remember at some point reading a comment by Sal about the increased rigidity gained by using a shouldered pin construction that is held by screws. Maybe I’m not remembering this correctly, and Sal please correct me if I’m wrong here.

Either way, this knife feels incredibly solid especially for something this light. How light, you ask? Currently it weighs 79 grams, which funny enough is exactly what it weighed as a fixed blade blank with no handle. Honestly, I don’t think I’d want it much lighter than this or it might feel front heavy. I still need to add a pocket clip and contour the scales so the weight might change slightly but it shouldn’t be significant.

The one large change I am considering is doing a Smock style button actuated comp lock instead of the normal scale recess. The reason for this is that when you use the flipper the lock bar moves over and gives your finger a little pinch, which isn’t ideal. I’ve done a few PM2 button lock mods before, so making this change seems easily doable. On the bright side, the thing already flips and flicks very nicely. I’ll definitely do some fine tuning so it properly drops shut, but I’m very happy to have it perform like this straight away. Also, the lockup is rock solid with zero play

[Paul Ardbeg]

Awsome knife!! Sweet action

[Josh Crutchley]

Awesome work!

[clinton1]

I ended up making my backspacer out of Cocobolo just because I had some that was close to the correct thickness. The backspacer on this knife is pretty unique in that it isn’t just a spacer, but it also helps to anchor the lock bar. The two pieces are press fit together with two 1/8” 2-56 threaded connectors, which stiffens the whole assembly, and more importantly allowed me to take off the “show” scale and keep the lock bar in place. That made it possible to drill into the tang using the detent ball hole in the bar as a guide, which is how I always drill my tangs for a good detent. Here is a picture of the knife with the show scale removed to drill the aforementioned detent pocket in the tang (pivot screws is going through a temporary spacer to keep the blade/washer stack tight).



This is my first time using a shouldered stop pin and it basically dictates everything when it comes to spacing between the scales (washer/blade stack, pivot bushing, backspacer). It’s kind of a pain in the ***, but hopefully it is worth it. I remember at some point reading a comment by Sal about the increased rigidity gained by using a shouldered pin construction that is held by screws. Maybe I’m not remembering this correctly, and Sal please correct me if I’m wrong here.

Either way, this knife feels incredibly solid especially for something this light. How light, you ask? Currently it weighs 79 grams, which funny enough is exactly what it weighed as a fixed blade blank with no handle. Honestly, I don’t think I’d want it much lighter than this or it might feel front heavy. I still need to add a pocket clip and contour the scales so the weight might change slightly but it shouldn’t be significant.

The one large change I am considering is doing a Smock style button actuated comp lock instead of the normal scale recess. The reason for this is that when you use the flipper the lock bar moves over and gives your finger a little pinch, which isn’t ideal. I’ve done a few PM2 button lock mods before, so making this change seems easily doable. On the bright side, the thing already flips and flicks very nicely. I’ll definitely do some fine tuning so it properly drops shut, but I’m very happy to have it perform like this straight away. Also, the lockup is rock solid with zero play

That's amazing! Nicely done. Appreciate the updates and info!

[Bolster]

Excellent! May I ask how you made the complex and intricate shapes in the very hard steel of the tang? What tools can do this?

[CasperFatone]

Excellent! May I ask how you made the complex and intricate shapes in the very hard steel of the tang? What tools can do this?

The cuts in the tang are all done freehand with a Dremel, roughed in with a reinforced cutting disc and then ground with cheap carbide bits. For the disc cuts I clamp the blade down or put it in a vise, and keep a wet paper towel handy to cool the blade regularly. I used my 2x72 a little bit on this, but most of the spots on this were hard to grind on that because of the shape. The lock cut was finished out using a flat diamond needle file.

Here are some pictures of the blade in place with the show scale removed, and of the lock cut in the tang.

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[Ramonade]

This is as impressive as it is inspiring !

[Bolster]

Thanks for the info on grinding the intricate bits. So it sounds like high speed (Dremel or Foredom) type tools with a combo of cutting discs, carbide bits, CBN bits, and diamond bits would get the job done. The freehand level of accuracy you're able to obtain, is remarkable. I can see how the tang, where it contacts the lock bar, is nicely angled. Not too little; not too much.

[CasperFatone]

For these cuts I didn’t rely on a jig but just did the old fashioned method of creeping up on the fit. Similar to most of my hand done wood joinery I will cut away the bulk of the material first (in this case with the cutting disc) and then change over to something that removes material slower (carbide burrs) to get even closer to the fit, then do the last bit even slower (diamond files). The more times you do it the easier it becomes and the process takes less time. This knife was done slightly different than others I’ve done because I got the tang cut looking good, and then I made slight adjustments to the lock bar to get it operating the way I wanted.

I spent some more time tuning the action so that it flips reliably and have it almost where I want it to be. It’s always a delicate dance of changing the depth of the detent ball, the lock bar tension, and adjusting the “relief” cut in the lock bar. Since I don’t have a mill I usually don’t do a traditional relief cut, but instead drill a hole through the lock bar at the bend, starting small and slowly increase the size until I have it where I want it. If the bar is too stiff or the detent ball sits too deep in the tang you might have a knife that flips reliably but flicking it will be too difficult. If the bar is too flexible or the ball doesn’t sit deep enough you might have a knife that flicks well but doesn’t deploy with enough force to flip reliably. I’m sure there is an actual formula for getting this right, but there are several factors to consider like lock bar length, blade weight, and friction at the pivot. The last one is probably why most flippers run on bearings, but I tend to strongly prefer a washer/pivot bushing setup for actual use.

[CasperFatone]

Got the action tuned just the way I want it with no blade play

Now I just need to make a clip and figure out how I want to contour and finish off the scales. I’m tempted to do a pattern similar to the Lotus style PM2 scales, but don’t want to remove too much material for fear of introducing flex to the handle. Right now the thing is stiff as can be and I’d like to keep it that way.

[CasperFatone]

This one is all done, and I have to say I’m really pleased with how it turned out. Contouring the scales really made it feel good in my hand and gave so much better access to the Spydiehole for flicking. The Ti clip weighs almost nothing and the final weight is just under 80 grams, which is right about where it was when it came out of the box. I carried it today and love how light it is.





I figured I’d throw in a family photo as well :)