Lets see:
"type" : "recipe",
"result": "wrench",
"category": "CC_OTHER",
"subcategory": "CSC_OTHER_TOOLS",
"skill_used": "fabrication",
"difficulty": 4,
"time": 300000,
"reversible": false,
"autolearn": true,
"tools": [ [ ["hammer", -1], ["toolset", -1] ],
[
["tongs", -1]
],
[
["chisel", -1]
],
[
["anvil", -1]
],
[
["crucible", -1]
],
[
["forge", 200], ["char_forge", 40]
]
],
"components":
[
[
[ "steel_lump", 1 ],
[ "steel_chunk", 4 ],
[ "scrap", 12 ]
]
]
Nope, no wrench needed. Just need to find the other stuff 
Edit: this is the most recent experimental. So your recipe may vary.