Drengr Fieldstrip Folder Prototyping

More in-depth discussion on our inaugural product, the Drengr Folding Knife. Design goals, challenges, insight into what goes into making it.
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Aett Armorers-Chris
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Drengr Fieldstrip Folder Prototyping

Post by Aett Armorers-Chris » Sun Feb 17, 2019 1:52 am

This week was an incredibly successful and encouraging week on prototyping!

Skillsets required for both machining and design refinements have improved substantially and it is showing in the work. I should note that it is requiring every bit of my skill to get these results and I am learning new things along the way to get it where it needs to be.

The following are the first-ever views of the knife coming together:

Pic with the frame exterior machined for the first time!
I’ve machined both sides many times to fine tune the fit and function of the field strip feature, but this is the 1st run at machining the outside of the right hand (RH) Frame. I’m very happy with the initial results of machining the contours of the hilt and the stars on the scale mounts. This is prototyped in aluminum and the results are nearly as good as I could expect prior to polishing. Finish will be even better when done in titanium as it is designed for.

Close up of decorative star on scale mount and part of the machined hilt, prior to any polishing.
Really happy with these initial results, the hilt was a major challenge with all its contours. Refined CAM programming to get rid of those improper depth cuts. As the knife evolves, every operation is methodically checked and literally looked at through a magnifying glass to refine it.

The blade, its stop pin and lock lever are shown installed on RH frame.
The fit/lock-up between these components is critical to the overall quality of a knife. I am extremely happy with the results so far considering this is blade #1 without any of the further refinements I made later. Blade 1 did not have the bevel cut for lock lever at that point, so I had to hand grind that. Lock-up is slightly off because of hand grind and detent ball hole was accidentally ground.

What's really positive is that, since the very start, blade/blade stop pin fit has been unchanged and right on every time.

RH frame pivoting onto LH Frame.
I have done more machining and design adjustments concentrating on this feature than any other by far. Not only is it one of the unique/core features of this knife, it is also the most critical in contributing to the overall fit and function. I can now produce repeatable results without rattle or any minor misalignments of the frames.

Out of everything good that happened this week, this was the best!

Frames interlocked, blade locked in open position.
It’s a nice view of the hilt and star machining prior to polishing also. Blade is not the most current version and has since been refined for cosmetics. Blade lock lever I forgot to update model and machined an older version so it fits poorly. Since this, I have redesigned how the blade lock lever mounts to frame to increase support and prevent buckling. Looking forward to machining the updated versions next week!

Earlier version of RH frame which I hand-rubbed a little with 360 grit.
I do this to check surface finish after machining. If there are still tooling marks after a little rubbing, I consider it a fail and adjust speeds/feeds/tools/operation to minimize those marks as much as possible.

As I mentioned earlier, blade and blade stop pin fit has been right on and it shows. This is still blade #1 and it's in another frame fitting right on. Between 3 different frames and 4 different blades, this area consistently matches up. Very enthusiastic about that!

The RH frame, which is the foundation and most intricate part of the knife, is about 3 hours of CNC machining alone. In that 3 hours, there are 53 different CNC operations and over 30 tool changes to machine every minute detail to match the CAD design. Overall, the complete knife is looking at about 8 hours of machining time. Seeing the results of the extra efforts on attention to detail coming to life on the knife has been well worth it!

I’m very pleased on progress as I am now moving beyond the mechanical function and getting into refining the fit and aesthetics of the knife.

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