Knife Review: Spyderco Sliverax


Flashlight Enthusiast
May 5, 2010
Hove, UK
The Spyderco Sliverax is a design by automotive engineer and knife enthusiast Paul Alexander. It is the first production folding knife to combine a flipper opener with Spyderco's Compression Lock mechanism, and is Paul's second collaboration with Spyderco. Sleek lines and a pronounced positive rake to the blade give the Sliverax a distinctive and purposeful look.


Author's Statement for Transparency and Disclosure
The test sample/s featured in this article have been provided for technical testing and review by the manufacturer. Test samples are retained by the reviewer following publication of the completed review for the purposes of long term testing and product comparisons.

All output figures and test results published in this review are the sole work of the reviewer, and are carried out independently and without bias. Test results are reported as found, with no embellishments or alteration. Though best endeavours are made to maintain the accuracy of test equipment, the accuracy of these results is not guaranteed and is subject to the test equipment functioning correctly.

New Review Format 2018!

Tactical Reviews is known for very detailed reviews using many high quality images. This has meant quite a lot of scrolling to read most reviews. In the new format, the review contains 'responsive image galleries' to better display these images as a slide show with captions.
NOTE: Unfortunately these galleries cannot be pasted into forum threads.

A good look round the Sliverax:
Things to look out for here are included in the image captions.

(Moderators, there is a reciprocal link at the end of every review on Tactical Reviews.)

Explained by the Maker:
The reasons for certain design choices may not be clear when simply looking at an object, so this section is intended to give an insight into the thinking behind a design by speaking to the designer themselves.

From Spyderco's product description "Designed by automotive engineer and knife enthusiast Paul Alexander, the Sliverax is the first factory-made folding knife to combine Spyderco's Compression Lock™ mechanism with a flipper-style opener. Its sleek drop-point blade is crafted from CPM® S30V® stainless steel and proudly includes both a fully accessible Trademark Round Hole™ and an index-finger flipper to support a full spectrum of one-handed opening options with either hand. A full-flat grind gives it outstanding edge geometry and its slightly negative blade-to-handle angle enhances its cutting leverage and shortens its opening arc for swift, positive deployment.

The Sliverax's blade is supported by Spyderco's patented Compression Lock mechanism—a high-strength lock located in the spine of the handle to greatly reduce the risk of unintentional release during use. Its lightweight, open-backed handle design features stunning carbon fiber/G-10 laminate scales and nested stainless steel liners. This advanced construction style provides impressive structural strength, keeps the knife slim and pocket friendly, and offers a solid foundation for the knife's lock mechanism. To allow convenient carry and keep the Sliverax instantly accessible, its handle includes a reversible deep-pocket wire clip that can be configured for right or left-side tip-up carry."

The Blade and Handle Geometry:

Most knife specifications have a basic description of the blade geometry, but in this section I will be taking a more detailed look at geometry and balance.


Using a set of gauges and precision measuring equipment including a Vernier protractor, callipers, fixed radius gauges and the unique Arc Master adjustable radius gauge (the one that looks like a crossbow).

These measurements have been tabulated and are presented along with a few reference blades (8" Chef's Knife, 5.5" Santoku and the popular Fällkniven F1).

Key aspects such as the primary bevel angle, grind type, blade depth, blade thickness, length, weight are detailed, along with balance information.

The 'Balance relative to the front of the handle' tells you if the knife will feel front heavy, or if the weight is in your hand (a positive value means the weight is forward of the front of the handle). The 'Balance relative to the centre of the handle' indicates how close to a 'neutral balance' the knife has in the hand.

In the case of full convex grinds the approximate centre of the grind is used for the primary bevel angle estimate.

(Wherever you see the 'Read MORE' marker, it indicates that the Extended Version of the review has additional content at that point. Viewing the extended version helps support further reviews, but please ensure you return to this Forum for comments and discussion.)The blade is made from CPM S30V steel.

New for 2018! BESS Certified sharpness testing:

The BESS 'C' scale of sharpness, developed by Mike Brubacher (Brubacher Edge Sharpness Scale) will now become part of Tactical Reviews' knife testing process. Initially this will be used to verify the sharpness of the factory edge and allow the knife to be brought to a minimum standard sharpness before testing a blade's cutting performance.


The Sliverax's factory edge has an average BESS 'C' sharpness of 186. This is yet another super sharp factory edge from Spyderco. A figure less than 200 is really good and easily shaves arm hairs and falls through 80gsm paper.

What it is like to use?

What struck me on initially handling this knife is how the Sliverax differs from conventional folders with its organic lines and purposeful downward angled blade (positive rake).


When folded it is almost like a worry stone in its pleasing feel and curvy shape. Opening is lightning fast with the flipper, and this speed is in part due to the blade's positive rake, meaning the blade only has to rotate 160 degrees to open, instead of 180 degrees. Of course the pivot's captive ball bearings also guide the blade with virtually no resistance at all.

Having a fully exposed opening hole from both sides makes it very comfortable and easy to thumb-open with either hand. The clip can be fitted to either side, so the Sliverax is truly ambidextrous. The only aspect that is slightly handed is a one-handed close. I certainly found it easier to unlock the compression lock one handed using my right hand.

For the opening hole to be fully exposed, and to not have a Spyderco 'hump', a lot of the handle has been cut away making the handle at the first and second fingers very thin. As well as accentuating the rake of the blade further, it also makes a full hand grip a little awkward as the fingers don't have much to hold. However it does provide a deep finger guard so the chance your hand might slip forward is very low.

I tend to prefer thumb-opening blades for several reasons. In fact, in the UK where I am based, flippers are too close to switchblades for comfort, so a nicely controlled thumb-open goes down much better. This leads me to make an observation about the compression lock which I also noted on the Sharman. As I open the blade, my first finger tends to lie over the lock itself, and the lock bar often gives me a little nip as it snaps into place. A minor complaint and easily avoided (if you remember) but mentioned here as an observation.

Despite being a smooth finish, the Carbon Fibre/G-10 Laminate handle has enough texture to provide positive grip even when wet.

Even without the 'issue' of appearances in the UK, I am personally a bit tired of the flipper. A mechanism where you have to compromise your grip on the knife to be able to press on a flipper tab to literally flick the blade open. Flippers can and do fail to fully open or lock, so much like the fixed blade is your most reliable partner, the two-handed open or the properly thumbed-open blade that is positively taken all the way to the locked position, means you know 100% it is there. If safety and security are your primary aims, then open the blade by manually rotating it all the way.

This leads me nicely into a couple of modifications I have made to the Sliverax I've been testing. Firstly the removal of the flipper tab. This makes the Sliverax a no-question thumb operated OHO, and has the benefit of removing the protruding flipper tab so it is even more pocket friendly.

The second modification is one of those things that for me is the sign of a finished knife blade, a sharpening choil. Others will have different opinions, and I'm not saying I'm right, but it is my preference. The end of the cutting edge at the sharpening choil also provide another 'point' for fine accurate cuts, so is not purely an aesthetic addition, but is functional too.

These images are of the modification I made and posted on Instagram, hence the branding on the images.


In the modified state (allowing me to carry it more), this knife has proven itself over and over and has become a firm favourite. The positive rake makes the blade attack each cut eagerly, with the full flat grind slicing smoothly and efficiently. Its, lightness and pocket friendly finish and shape allow you to forget it is there until you need it. This is a knife I've gone from being uncertain of, to positively wanting to carry and use.

Review Summary

The views expressed in this summary table are from the point of view of the reviewer's personal use. I am not a member of the armed forces and cannot comment on its use beyond a cutting tool or field/hunting knife.

Something that might be a 'pro' for one user can be a 'con' for another, so the comments are categorised based on my requirements. You should consider all points and if they could be beneficial to you.

Things I like

Organic ergonomic flowing lines.
Full Flat Grind S30V blade.
Easy to access opening hole.
Super slick flipping action.
Lightweight and easy to carry.
Blade rake makes for a positive cutting action.

What doesn't work so well for me

Handle very thin where the first two fingers grip.
The Compression lock can 'nip' you.


(Moderators, there is a reciprocal link at the end of every review on Tactical Reviews.)



Hoka Hey

Newly Enlightened
Jul 28, 2018
Interesting knife. Maybe missed, but 150-160$ isn't bad for a quality s30v blade.

It's going to sound odd, but slightly dull, this might be a great skinning knife. I like the angle of attack.

I do like your mod on the flipper. Looks much better.


Newly Enlightened
Feb 26, 2020
cant wait to get my hands on this and the Astute, anyone know if Sliverax will be limited addition or mass produced?