/ combat chainsaw (off) can be crafted with the following recipes

Autolearned
Player Recipe
Primary skill used: mechanics(6)
Required skills: melee(2)
Time to complete: 30 minutes
Tools required:
> 1 tool with hammering quality of 2
> 1 tool with metal sawing quality of 1
> 1 tool with screw driving quality of 1
> 1 tool with bolt turning quality of 1
> 1 tool with glare protection quality of 2
> arc welder (100 charges) OR makeshift arc welder (150 charges) OR integrated toolset (150 charges) OR acetylene torch (20 charges)
Components required:
> 1x chainsaw (off)
> 1x metal tank (2L)
> 3x chunk of steel OR 9x scrap metal
Byproducts:
(none)
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This recipe can be found in the following books when mechanics is at least the required level:
Mechanical Mastery (level 4)
The Streetfighter's Sidekick (level 5)