The Grinder in Borderlands: The Presequel (BL:TPS). Insert three items if you want to grind at this machine!
Before loading items in the Grinder
After adding 3 weapons to the Grinder
The Grinder produced a legendary pistol

These are all the Grinder Recipes in Borderlands: The Pre-Sequel

You can find the Grinder in Janey Springs' workshop in Concordia. You can use it after you complete the side-quest Grinders

Credit: Got lots of the info below from BTHRZeroX's post on reddit

Basic Weapons[edit]

Note: If you don't moonstone grind, you have a chance of getting a weapon of rarity one level below the one you wanted (for example purple instead of orange, blue instead of purple, etc)

  • Green Weapon - 2 White weapons of desired type + 1 additional White random weapon
  • Blue Weapon - 2 Green weapons of desired type + 1 additional Green random weapon
  • Purple Weapon - 2 Blue weapons of desired type + 1 additional Blue random weapon
  • Legendary Weapon - Has to be 3 legendary weapons

Random Weapons[edit]

  • Green Weapon - 3 White weapons of different types
  • Blue Weapon - 3 Green weapons of different types
  • Purple Weapon - 3 Blue weapons of different types
  • Legendary Weapon - 3 Legendarys, 2 Legendarys and a Purple of the same type as your desired legendary (ie Pistol, Shotgun ect), or 3 purples of different types

Assault Rifle[edit]

  • 1 SMG + 1 Sniper Rifle + 1 Shield, All White
  • 1 SMG + 1 Sniper Rifle + 1 Shield, All Green
  • 1 SMG + 1 Sniper Rifle + 1 Shield, All Blue

Rocket Launcher[edit]

  • 2 weapons + 1 Grenade Mod, All White
  • 2 weapons + 1 Grenade Mod, All Green
  • 2 weapons + 1 Grenade Mod, All Blue

Shotgun[edit]

  • 1 Pistol + 1 SMG + 1 Shield, All White
  • 1 Pistol + 1 SMG + 1 Shield, All Green
  • 1 Pistol + 1 SMG + 1 Shield, All Blue

SMG[edit]

  • 1 Assault Rifle + 1 Pistol+ 1 Shield, All White
  • 1 Assault Rifle + 1 Pistol+ 1 Shield, All Green
  • 1 Assault Rifle + 1 Pistol+ 1 Shield, All Blue

Sniper Rifle[edit]

  • 1 Assault Rifle + 1 Shotgun + 1 Shield, All White
  • 1 Assault Rifle + 1 Shotgun + 1 Shield, All Green
  • 1 Assault Rifle + 1 Shotgun + 1 Shield, All Blue

Oz Kits[edit]

Note: Unless moonstone is added, you risk getting an item of same rarity

  • Any 3 Oz Kits, All White
  • Any 3 Oz Kits, All Green
  • Any 3 Oz Kits, All Blue

Shield[edit]

Note: Unless moonstone is added, you risk getting an item of lower rarity

  • Any 3 Shields, All White
  • Any 3 Shields, All Green
  • Any 3 Shields, All Blue

Grenade Mods[edit]

Note: Unless moonstone is added, you risk getting an item of lower rarity

  • Any 3 Grenade Mods, All White
  • Any 3 Grenade Mods, All Green
  • Any 3 Grenade Mods, All Blue

Moonstone Bonuses[edit]

Use Moonstones in the Grinder to get bonuses for your items:

  • Fast Learner – Bonus to XP from kills
  • Harden Up – Improves maximum shields
  • Boominator – Increases grenade damage
  • Safeguard – Restores some of your shields on each kill
  • Oxygenator – Damaging enemies restores Oxygen
  • Piercing Rounds – Grants a chance to ignore enemy shields
  • Punisher – Raises critical hit damage
  • Serenity – Reduces rate of O2 consumption