Here are a few tips on how to effciently use furnaces.
For a start when using small furnaces, you will want to set up your furnace, so that you are smelting the most ore for your wood without chance of loss, as starting on new server or wipe cycle, can be hard unless you have a metal door and code lock.
These large furnaces smelting designs will safly hold all of the ore smelted and charcoal.

0 hours 33 minutes 20 seconds.
Time=33:20, Metal ore=600,




0 hours 25 minutes 0 seconds.
Time=25:00, Sulphur ore=900,




0 hours 33 minutes 20 seconds
T=33:20, High Quality Metal ore=216




0 hours 33 minutes 20 seconds
T=33:20, High Quality Metal ore=200

1k wood = 2.80 metalfrags per wood.
0 hours, 33 minutes, 20 seconds.
Time=33:20, Metal Ore=2804, Sulphur Ore=5106, High Quality Metal Ore=977.

2k wood = 2.39 metalfrags per wood.
1 hours, 6 minutes, 40 seconds.
Time=66:40, Metal Ore=4772, Sulphur Ore=7985,

Note: The 500 wood HAS to be put in FIRST otherwise it will not work.
1 hours, 23 minutes, 30 seconds.
Time=83:30, Sulphur Ore=8759,

3k wood = 2.03 metalfrags per wood.
1 hours, 40 minutes, 0 seconds.
Time=100:00, Metal Ore=6087,

4k wood = 1.72 metalfrags per wood.
2 hours, 13 minutes, 20 seconds.
Time=133:20, Metal Ore=6879,

5k wood = 1.46 metalfrags per wood.
2 hours, 46 minutes, 40 seconds.
Time=166:40, Metal Ore=7314,

20 Wood smelts 3 Crude Oil or 6,2/3 Wood per 1 Crude Oil
1 Wood burns for 1.5 seconds, 1 Crude Oil needs 10 seconds to cook.
Time = 0 Hours 25 Minutes 0 Seconds
Wood = 1000, Crude Oil = 344, Low Grade Fuel = 1032

Warning the 300 Wood has to be put in first,
Time = 0 Hours 32 Minutes 30 Seconds
Wood = 1300, Crude Oil = 361, Low Grade Fuel = 1083

• 1 wood takes 2 seconds to burn in any furnace.
  
• 1 metal ore needs 5 wood to smelt.
  
• 1 sulphur ore needs 2.5 wood to smelt.
  
• 1 high quality metal ore needs 10 wood to smelt.
  
• 1 wood has 70% to 80% chance to make charcoal or simply 75%.
  
• Each slot smelts 1 ore each at the same time.
  
• Adding more ore than shown into large furnaces will break it, Adding less ore then shown will still work fine.