About

Titanium Framelock Folder

Project: Mid 2025

Writeup: September 2025

Aw, flowers <3

My first folding knife design. Designed from scratch and built entirely by hand, featuring:

I'm not claiming that this is the best or most beautiful design ever, nor that it's particularly original. I've taken inspiration and design ideas from a load of similar knives by great designers. I mostly just wanted to see if I could pull off my own version.

I've always appreciated the elegance of Chris Reeve's legendary "Reeve Integral Lock" design. Now widely copied, you often hear them referred to as "frame locks" because the primary element stopping the blade from closing is a flexible portion of the knife's frame itself. A very efficient design with a minimum of moving parts, with the strength and satisfying feeling of the lockup being absolutely unparalleled when implemented properly. So when I started thinking about my own folder design, I pretty much immediately went with the framelock concept.

Considering hand modelling...

I quickly realised that the design and manufacturing considerations are many times more complex with folders than with nice simple fixed-blades. You have a whole world of inter-related variables around the opening and closing mechanism that impact performance and handling, that you somehow have to balance and compromise with the aesthetics and ergonomics of the various parts. I spent many late nights in the CAD black-hole, moving splines back and forwards before I finally landed on a design that would theoretically work, I theoretically liked the look of, and I could theoretically manufacture in my small garage.

Looking at this first one, it's a miracle I managed to pull this off

This is where my series of side-quests began. My early prototypes were really suffering from lack of precision: a mounting hole being 0.5mm out of position on a fixed blade is basically unnoticeable, and can be reasonably accommodated by adjusting the scales or handle holes to match. But a similar inaccuracy here essentially renders the whole part scrapped. Or at the very best requiring an individual hand-fudging to multiple parts which might mean you can actually assemble the thing, but it now doesn't match the plans and your carefully designed clearances and mechanism no longer work.

So side-quest sub-project 1 was to devise a better method of laying out my paper plans onto the physical materials. I've tried a load of different solutions this year, having become frustrated with the old-faithful "glue the printer paper to the metal" technique on the kitchen knife. With the paper wearing or burning off or getting sodden with oil, it's impossible to actually hit your lines. But I eventually stumbled upon quite a reliable method of transferring the actual printed toner to the metal via the application of acetone under mild heating:

Toner-transfer used for marking out.

This leaves you with an incredibly sharp and durable line which resists heating while grinding. Holes can also be center-punched to within 0.1 - 0.2mm of spec (I'm guessing here) with an optical center-punch. Which turns out to be good enough for the whole thing to go together. I still have room for improvement here, which I hope will come with practice. It turns out that this technique is known as "toner transfer" and can be used for PCB manufacturing which needs to achieve even greater resolution and coverage accuracy than I need for marking out! Room to improve my process here too.

Other than drill-hole placement, I also had the need to accurately depth holes. Both the opening and closing detents and aesthetics of the external screws all rely on accurate and consistent depths, which I had never really needed before. Which brings us to side-quest number 2: upgrading the drill-press!

Thrilling drilling

Here you can see I managed to fashion a DRO (digital readout) from a cheap pair of calipers, and added a worklight to illuminate the target spot, both powered with a DC supply mounted inside the housing and sharing the drill's AC input. So no coin-cells to run out! You can just about see the separate switch nicely mounted underneath the motor power in the photo above. I also overcame my commitment issues and screwed the whole thing down to the worktop to minimise jiggling. All of these combined means that I can theoretically accurately hit the spot I just centerpunched and drill to a consistent known depth.

Which brings us to the third and final side-quest: that big beautiful slot!

0.5mm slot forming the framelock spring

This slot is what allows the spring portion of the frame to move inwards and apply the locking force to the blade. I really wanted to keep this as small and elegant as possible, and avoid any clearance holes at the end and corners of the slot. I suppose these holes simplify manufacturing, but I find them a little bit ugly. See the SpydieChef™ (which I love) for an example of a very generous wide slot and clearance holes. I wanted to shoot for something a little tighter and cleaner.

Some early success with 0.5mm HSS slitting saws in the drill-press (see third prototype on the green cutting mat photo above) gave me confidence that this thin little slot was actually doable. I just had to devise a process which was reliable and safer than manually moving the vise and frame under the spinning blade (which I'm NOT going to show). Enter the compound vise!

Restored XY compound vise

This was the smallest compound vise I'd ever come across, with only a 75mm jaw-width. Picked it up on eBay very reasonably because it had some parts missing. Two new hardened jaws and a handle later (guess which one is mine...) and I could accurately cut the bulk of the slot without breaking saws or raising my blood-pressure to previously unknown levels. You can't cut the whole thing all the way through because you can't get the blade right on the center-line of the saw because the arbor is in the way. But it was easy enough to connect the two slots using a modified wide hacksaw blade once the slitting saw has cut a nice guide line most of the way through.

The final knife in the pretty photos above is the 6th major design revision and the product of 3 completed prototypes and 5 or 6 sets of frames which didn't make it that far! It was always such a relief to get past cutting the slot knowing that the hard parts were (mostly) done. I took a few rounds of iteration to come up with the style of chamfer and type of finish I liked on the frame scales:

Early prototype sandblasted frames

Sandblasted titanium looks and feels excellent. Fresh out of blasting it's very bright white and almost sparkles with all the different micro-facets. But with a little handling and a light oil, you get the nice titanium grey and lovely smooth but grippy handfeel. I haven't yet experimented with anodising on top of this sandblast. Ideas ideas...

Clippy!

The clip also needed a few design revisions. I eventually landed on this relatively thin design in the same sandblasted finish as the frames. The polished titanium and brass variants were interesting but a bit too audacious for me...

There's a hidden pin below the clip screw so the whole thing can't spin around. Adds a very reassuring interference fit, but needed to be absolutely perfectly accurate to work!

Memories of hand sanding...

I thought I'd make things extra difficult for myself on this first successful one and do a high-polish on the blade. Remember that this ASP-2053 is specifically designed to be highly abrasive and wear resistant! Definitely took me a fair few hours, and gave me knifemaker's elbow. It's not a full mirror polish, but it's good enough for me. I'll be interested to see how the ASP holds up (I usually stonewash for the nice dark finish). It really goes well with the stainless hardware.

Maybe I should try one with one carbon-fibre left frame and a dark stonewashed blade and hardware...

This gives you an idea of how the framelock works. Ignore my wobbly chamfer lines - at least you can tell it's handmade.

Here we can see the inside of the knife in the open position. The lock bar springs downwards and the ball bearing rides against a precisely-angled part of the blade. The bearing is interference fit into the titanium frame and protrudes into the front slot. As you can imagine, the precise positioning of the bearing relative to the back of the blade, the angle of the angled portion, the spring tension of the lockbar, and polish and roundovers on the blade part all play a huge part in the handfeel of using the mechanism. It took a lot of revisions to get right. It's a lot of work, but I'm really happy with this one.

There's a similar number of variables on the closing detent. There's a blind hole on the pivot portion of the blade which the ball bearing rests in, which gives a satisfying click when it lands closed (at the same point the back of the blade comes to rest on the brass stop-pin), and also lets the lockbar sit flush with the rest of the frame. The size of this blind hole as well as the spring tension determine the blade's resistance to opening.

I didn't invent this ball-bearing concept obviously, it's all copied from the Chris Reeve Inkosi (hey, if it ain't broke...). But I had to figure out all the geometry for my design. And fitting the ball directly into the frame definitely has manufacturing and design advantages compared to a more complicated lockbar insert or just going raw frame-on-blade.

Wouldn't be one of mine without some brass somewhere

Here you can see the brass backspacer and stop-pin. I like the little pop of colour.

After I finished all the photos, I had some fun using the blade finally! Very very happy with the performance. The polish definitely adds a certain smoothness, and the steel is incredible as ever.

When I finally finished this piece which I'm about 95% happy with, I was very relieved to take a break from the folder project for a while! But now I'm almost through the recovery period, I'm sure it won't be long before the next revision...