Switch Axe Overview

The Switch Axe (スラッシュアックス Surasshuakkusu) is a Blademaster weapon class first introduced in MH Tri, and is present in MHP3rd, MH3U, MH4 and MH4U.

Official description : A powerful melee weapon, capable of such momentum that the hunter swinging it is dragged around by the momentum of each swing. Described as a marvel of technology capable of phantasmagorical might.

The weapon has transformation capabilities, with one blade shifting while being sheathed as well as sliding to a different position to change its attack style. In its secondary form, the weapon behaves far differently from its standard variation and uses a phial of specialized coating to add certain effects to the weapon. The weapon is also able to overload this phial, ending in a concentrated burst. 

The true power of the weapon is its versatility, with the 2 different forms and the combos to link the two types together. Rather than dodge rolling, the Switch Axe has a quick step to the side, allowing the user to keep focused on his attack while keeping out of harm's reach.

It consists of two forms: Axe and Sword. The axe possesses a great range and can hit difficult-to-reach parts of the monsters very easily, especially with the rising slash which can even hit a Rath's wing while it is flying. It also has a potentially infinite combo which is limited by stamina. It consists of swinging the axe very quickly from left to right and right to left after a rising slash. Apart from that, its power and mobility are similar to Long Sword without spirit bar effects.

The Sword mode, which uses the phial, looks similar to Great Sword in form, but is a much faster weapon with less powerful attacks when compared to GS. The player can simply hit with vertical or horizontal combos to benefit from the phial effect, and can also make a concentrated burst (or discharge): after a forward slash, the weapon will rise while dealing damage, then produce a powerful explosion which produces recoil and makes the weapon revert to axe mode. Of course, this move will still benefit from the phial effect.

The time spent in Sword mode is limited to an energy meter found under the Sharpness indicator. The bar only decreases when the weapon is swung while in Sword mode. Of course, standing around and looking at your marvelous Switch Axe in Sword mode does little to slay your target. Once this energy bar is depleted, the weapon will change back into Axe form and will need to be reloaded before going back into Sword form. The energy meter automatically recovers over time, but can be "reloaded" 40% by attempting to switch to sword mode while below 50% charge. 

- Phials

Every switch axe is imbued with one type of phial, which boosts their capabilities while in sword mode. The types and effects of the phials are as follows:

• Power Phial: A phial that boosts the raw power of a Switch Axe's sword mode. One of the more common phials.
• Element Phial: A phial that boosts the natural elemental/status power of a Switch Axe in sword mode. Only Switch Axes with natural element/status can have this phial.
• Dragon Phial: A phial that gives a Switch Axe a fixed amount of Dragon Element in sword mode. Since natural Dragon Element is very rare among Switch Axes, these weapons are treated as quick substitutions. Switch Axes with this phial are always Raw, and  have Dragon Element as their latent elemental power.
• Poison Phial: A phial for raw Switch Axes, giving them venomous properties in sword mode. Switch Axes with this phial always have the Poison status as their hidden latent power.
• Paralysis Phial: A phial for raw Switch Axes, giving them potential paralytic effects in sword mode. Switch Axes with this phial always have the Paralysis status as their hidden latent power.
• Exhaust Phial: A unique, raw-exclusive Switch Axe Phial that famously only come from the "Wild Axe" branches. It gives a Switch Axe the ability to drain boss monsters' stamina on select attacks, making them more prone to exhaustion while also being able to stun monsters if sufficiently hitting the head like impact attacks. They still are able to cut tails like slice attacks. However, Switch Axes with this phial have no hidden latent power that can be activated with the "Awakening" skill.

- Pros and Cons :

Pros

• Allows for easy evasion skills.
• Sword Mode features built-in ESP.
• Attacks come out relatively quick, and attacks even faster in Sword Mode.
• Can switch modes mid-combo.
• All of its combos are infinite.
• Doesn't require good precision.
• Axe Mode's upswing attack has the highest range of any blademaster weapon.

Cons

• Loses sharpness faster than average.
• It's most powerful attacks are disruptive to other hunters.
• Seems to be a tad underpowered in Tri, although does slightly more damage overall in p3rd.
• Combos are rather hard to get out of; another con that has been removed in p3rd.
• Mobility is rather limited in axe mode, and has the same mobility of a great sword in sword mode.
• Lacks a guard.

- Tutorial for Beginner Hunter (by GaijinHunter)

https://www.youtube.com/watch?v=ZRv1_mGf2R8