Precision Crafting allows players to craft items in specific quantities. This allows them to use less resources and avoid crafting excess items.

For example, the iron bars recipe requires 6 iron ingots and makes 16 iron bars. In vanilla, if the player only needed 8 iron bars, they would end up with 8 excess iron bars. The excess iron bars are effectively 3 iron ingots lost, plus they will take up space in chests unless disposed of.

With Precision Crafting, the player could craft exactly 8 iron bars using the Precision Crafting Table. This would save them 3 iron ingots and avoid excess iron bars.

Precision Crafting Table Recipe

Usage

1 - Crafting Pattern Slots

2 - Output Slot

3 - Quantity Field & Quantity Adjustment Buttons

4 - Ingredient Slots

5 - Player Inventory & Hotbar Slots

Steps:

Set the recipe to be used by placing items into the Crafting Pattern Slots. They are ghost/fake slots so the stack you click on them with will stay the same size. Double left clicking or shift-clicking on a pattern slot will clear all pattern slots.
Use the arrows above and below the Quantity Field to set the quantity of outputs you want, or type into the quantity field.
The required ingredients and their quantities will be displayed below the Ingredient Slots as partly transparent itemstacks. If an ingredient accepts more one stack(e.g ore dictionary ingredients) then it will cycle through all the itemstacks it accepts. Ingredients that have been satisfied will stop displaying. Place each ingredient in the slot directly above the the corresponding displayed itemstack.
Once all ingredients are satisfied, you will be able to remove the outputs from the Output Slot.

Notes:

Required ingredient quantities are rounded up to the nearest integer. The table will consume exactly this amount, excess ingredients beyond this amount will remain in the slots. This means that although crafting 4 iron bars should require 1.5 iron ingots, the table will consume 2.
The table only works with standard recipes (shaped or shapeless recipes with no custom logic). Ore Dictionary recipes are considered standard recipes. Recipes that use custom logic, like leather armour dying or firework star crafting do not function as they are highly likely to result in exploits otherwise.