EXTREMA RATIO RAO II

(BAD ASS FOLDER/FIXED BLADE)
an in depth review

Extrema Ratio's RAOII is a heavy duty folder using a spring loaded sliding bolt action to lock the blade open (Figure 1). This bolt is ambidextrous. It is a kind of axis lock but in this case the axis is perpendicular to the major axis of the knife, so unlike a typical axis lock which is quite good, it is possible that your fingers can actuate the release of the lock under some circumstances since the axis of the "axis lock" runs in the same direction as "slipping fingers" might move. Here on the RAO II however, if your fingers moved slipping forwards or backwards and pressed against the locking bolt then nothing would happen as the axis is in the vertical plane (and under spring tension too). Smart design improvement I'd say! 

Figure 1. The locking bolt is the one seen on the far right with the Torx head

It is not necessary to touch this bolt in order to open the blade but it is necessary to lift the bolt against it's spring action in order to close the knife.

This is no woosy folder! and is marketed under Extrema Ratio's "Molto Pesanti" line of folders which roughly translated in context into very heavy duty folder!  The RAO II weighs in at 322gm or 11.36 Oz. The spine at it's thickest part was measured at 6.12mm or about 0.240 of an inch, 

Closed view of the knife spine

basically a 1/4 inch thick! The blade is a drop point and runs at about full thickness to within about 17mm from the tip, so this makes the blade very strong in this area. A fuller sits just below thumb/finger gimping and aids blade opening.

Drop point blade geometry with swedge (Note fuller machined below the thumb gimping)

How does the RAO II Feel?

Ok as all of you know I don't like to test knives of any sorts wearing gloves. But to recap why...... If you have to wear gloves to  use a knife, fixed or folder then the designer has failed. Yes sure, gloves can be worn in cold to sub-zero temperatures or where the ambient rises to the 30's plus ie 86F or above and you've left the knife in the sun for a bit, then it's going to get hot as!

So do I need to wear gloves with this knife? No, is my simple answer. 

The surface of any knife handle which needs to be comfortable in the grip is the UPPER surface in the first instance. WHY? Because the upper surface is in direct contact with where the user pressure is focused from the palm, and the lower part is where your fingers are applying pressure for gripping and of course opposing pressure to retain the handle in place. As the handle region of the RAOII presents a flat profile with  generous radiuses on all surfaces, twisting motion is not going to happen. 

The RAO II does not operate on a liner lock system but as stated above on a vertical locking sliding bolt action, this makes for a very strong locking system. 

Construction Materials

Extrema Ratio use Böhler’s N690 Cobalt martensitic stainless alloy for the blade at HRC 58. The handle scales are machined from the 6000 series aluminium alloys, 6082. 6082 has the highest strength in the 6000 series of alloys and excellent corrosion resistance (Reference). Now this 6082 must be tough. 6065 has been routinely used in producing super strong and tough downhill mountain biking frames and rock climbing gear both of which  you have to trust your life with. All other parts in the knife construction such as screws etc are according to Extrema Ratio very corrosion resistant.

The main pivot is stainless steel. Brass washers are used, NOT Teflon. This will give the best possible characteristics and is usually done on the best folding knives.

Non reflective mil spec Mil C 13924 on the blade and black anodized for the handle scales to a thickness of 20 microns.
The material where RAOII appears is also made from N690 with the same characteristics to that of the blade.

 Where are forces applied?

Opening and closing there is a reassuring engagement of the locking mechanism unlike some liner lock systems where the spring tensioned liner must engage with the base of the blade. In the liner lock, if not super precise engagement then it is possible for the liner to either travel: almost past the width of the blade, not cover it enough, sit correctly in the middle or not engage properly at all and require some "tweaking". Sometimes manufacturers state there is a "wearing in period"  or the need to push the liner into position on a new knife. 
The mechanism of the RAO II doesn't require such a wearing in period and the user can easily visualize at first glance (there is an audible click too) correct engagement of the blade, as it will be sitting flush against the back spine.

Locking bolt (Torx head) in bottom position (fully locked) and lower safety pin for Fixed blade operation in place

Downward pressure on the spine, as applied by a cutting or pressing motion via gripping the handle is countered by the immovable tang back (The part where you see RAO II laser engraved on the above image of the handle) Therefore, it is impossible for the knife blade to move in upwards direction past this stop.

Forces applied in the opposite direction will tend to want to make the locking bolt (Figure 1.) 

Figure 1. Locking bolt and view of locking bolt spring mechanism

move in a direction towards the knife tip. This is of course impossible too, as the bolt has no where to travel in this direction. A small spring (seen here within the lock mechanism) keeps pressure against the locking bolt  (Figure 5a and 5b.) Finally there is a slight angle on the blade notch

Blade locking notch, note a slight acute angle (less than 90 degrees)

which will also force the locking bolt to only want to move in a forward and NOT a vertical direction.

Figure 5a side view from bolt head

Figure 5b end view

Further as a failsafe, a separate safety pin 

 can be screwed into one side of the 6082 alloy handles. Once this pin is inserted the RAOII essentially functions a "fixed blade knife" image required!

Pros

The RAO II's construction  appears to be very good and that's what I'd expect from a company such as Extrema Ratio. The tolerances are tight as. No lateral or vertical wobble of the blade either closed or open.

Out of the box the Extrema Ratio RAO II came surgically deadly sharp with little evidence of grind marks on what was almost a polished edge. As I've said in previous blogs, this is testament to a company of skilled workers.

 They have in place a small set screw to lock the main  pivot bolt after small adjustments.

Small set/locking screw stops the main pivot bolt from becoming loose

 Both this screw and the main bolt have flat head screw driver slots. This latter point from a field maintenance issue is better than using Torx head or Allen (socket head) bolts. WHY?? Because you can improvise if necessary to loosen these screws. It is virtually impossible to improvise on Torx head or Allen socket heads unless you have the actual tool. Just try it and see what happens.

When closed but without the locking pin inserted, the blade does not want to come out of the handle. This is a very important point if carrying this knife out of the supplied pouch/sheath for obvious safety aspects. Of course in the closed position and safety pin inserted then even under a rough and tumble situation the blade is going to be staying put and not injuring the user.

Metal to Metal

The contact surfaces, that is the back of the tang and the roller/axis lock pin (not to be confused with the supplementary locking pin) are not of two vastly different metal alloys. For example, when you have Titanium liner lock rubbing against the much hardened back end part of the tang then the softer metal ( the Ti) will tend to wear and this wear will depend on the abuse the knife mechanism sees over time and cause slop or hysteresis (the technical term for a sloppy mechanism) to occur. Not the case in this mechanism used in the RAOII.

The blade has a simple but great design. A Drop point, measuring 6.01mm across it's thickest section where the finger thumb gimping occurs.

The blade fuller has dual role, it is also used to open the knife via the thumb.

You can do all the fancy pants flicking this knife open business, if you have only one hand in operation. I'm not a big fan of this action, (with this particular knife) unless you are trained in knife fighting or using this knife in some action movie then  usually this operation is limited to  the  "show offs" out there. Also this simply puts unnecessary wear and tear on the mechanism plus makes a lot of noise.

The RAOII can be carried in the locked position closed simply by inserting the locking  pin. This makes carrying this knife in the folded position very safe as it is impossible for the blade  becoming "accidentally" open.

Portability

The RAO II is, after all a heavily built folder, without a belt clip. Something that you would expect on an EDC folder BUT you can carry this knife in your pocket as long as it's not in its carry system. I've done it no problems and you don't need ginormous pockets to do so!

The carry system is just great. Molle compatible, comes with a diamond plate sharpener for field sharpening (personally I'd use a finer grade to sharpen this blade when back at base). No uneven or loose stitching was present and tough ballistic nylon

Since the RAO II can be safely locked in the fixed position, the sheath accommodates carrying this knife as standard fixed blade. This also means that if by chance you were unable to close the blade, then transportation would be no problems from a functional and more importantly a safety issue.

Cons

ALL folding knives, full stop, are subject to dirt ingress no matter what the design. This is  simply a consequence of a folding mechanism and numerous moving parts capable of trapping dirt and possibly retaining this dirt, which may or may not compromise the function of the knife. Using a folding knife requires one to understand the maintenance requirements for such a knife. Once these things are understood then the user can enjoy many years of trouble free usage. Failure to do so can lead to malfunction and premature wearing of parts with the worst case scenario leading to personal injury.

What about Lubrication?
ER recommend good quality gun oils. Yep no problems there, however, I have been using top quality mountain biking lubricants on folding knives I own for many many years. WHY? Because these lubricants are designed not to attract dust and dirt; repel water; provide lubrication under extreme stress; not cake up and form a gooey mess, help prevent corrosion and my folders have never undergone the punishment my Free Ride bike took.

Now all that being said, how does the RAOII stack up? To be honest right now the blade is about to undergo vigorous field testing, so all I can present at this moment is opinion based on my experience in using this knife for a day on seasoned wood.

Dirt being allowed to sit between the handle scales, will, like any folder, introduce mater into moving parts. Simply keeping this area clean, will, like any folder, allow normal operation. Because the RAOII's handle width is much greater than a "regular  (EDC) folder", it should be easier to remove such "dirt".

Blade locking notch top view

Blade notch end view

Blade locking notch side view

I found the slightest of slightest movement under locked situation in the vertical plane and absolutely no movement laterally at all. 
After using the RAOII for a day on fully seasoned ELM ( a hardwood) I was confident in the locking mechanism (without the safety pin in use) and using the safety pin, well this just instills total confidence in this folder/fixed blade.

If and I say if, the small spring should break or become inoperable then the RAO II could only safely be used as a fixed blade with the locking pin inserted. As this is a new model and I have no data on the springs lifetime ( I will be asking ER about this) I can't say anymore. I only mention this as any locking folder from any manufacturer, if the locking mechanism becomes unusable then the safe use of the knife may not be possible. In the case of the design of the RAOII, it could be safely used without noticing any difference simply by using it in it's dual role as a fixed blade provided that locking pin is screwed in.

The stainless steel locking pin

Stainless Steel locking pin

could get lost if the elastic was to break. NO big deal, many things could be inserted into the hole as improvisation dictated. Some people might say the twisting of the shock cord is a big pain, 

Twisted Shock cord jointing safety locking pin to lanyard hole

well one thing, it aids undoing this pin in a hurry as the reverse twisting motion aids removal. IF you don't like it then you could simply put a good quality stainless alloy fishing swivel in place and hey presto! No more twisting of the shock cord but then you have to tediously undo the pin.

A full on Video Field Review is coming up shortly so stay tuned to Bushcampingtools.

This post is in part  inspired by Richard Basehart's character, Admiral Nelson in Irwin Allen's Voyage to the Bottom of the Sea, where he takes his service pen knife and: cuts down large palm fronds to make a splint for a comrades broken leg, cuts and makes a flag pole to attract attention; parachute cord and canopy material and uses it to build a signal fire (by cutting down more green palm fronds. In other words he uses a pen knife for a survival (albeit fictional) situation but not unrealistic work for pen knife/Folder.