Inspired by Caethan's comment, I came up with recipes for repairing metal armor. These are for a lossy process, where you need more materials than the final weight of the gear. To me, this represents crude repairs that an amateur smith might make: cutting out damaged lames and lacing in better ones from other armor scraps, riveting good links of mail into a damaged piece, and crudely welding/riveting patches onto a helmet.
As far as I can tell, there's no way to specify a recipe where you take an item and then need to add wildcard items until the combined weight reaches some value. The URW engine obviously knows how to do that, because the existing Repair function does that, but that function isn't available to mods.
[SUBMENU_START:Clothing]
.Repair lamellar cuirass. "Lamellar Cuirass" [effort:2] [phys:arms,hands] *CARPENTRY* /3h/ %-70% |+1|
{Lamellar *} #16.5# [remove] 'Lamellar scraps'
{Leather *} #3# [remove] 'Leather scraps for backing'
{Knife} <Small Knife>
[NAME:Lamellar Cuirass]
.Repair lamellar long hauberk. "Hunting Horn" [effort:2] [phys:arms,hands] *CARPENTRY* /8h/ %-70% |+1|
{Lamellar *} #46# [remove] 'Lamellar scraps'
{Leather *} #8# [remove] 'Leather scraps for backing'
{Knife} <Small Knife>
[NAME:Lamellar Long Hauberk]
[TILEGFX:armour]
[TYPE:armour]
[WEIGHT:40]
[ARMOUR_MATERIAL:lamellar]
[ARMOUR_COVERAGE:long_hauberk]
.Repair mail hauberk. "Mail Hauberk" [effort:3] [phys:arms,hands] *CARPENTRY* /5h/ %-70% |+1|
{Mail *} #27.5# [remove] 'Mail scraps'
{Cloth} #2.5# [remove] 'Cloth for padding'
{Wrought Iron} #1# [remove]
{Knife} <Small Knife>
{Iron Hammer}
{Iron Tongs}
[NAME:Mail Hauberk]
.Repair iron helm. "Iron Helm" [effort:4] [phys:arms,hands] *CARPENTRY* /45/ %-70% |+1|
{Iron *} #3# [remove] 'Iron scraps'
{Wrought Iron} #1.5# [remove]
{Charcoal} #18# [remove] [ground]
{Iron Hammer}
{Iron Tongs}
{Forge} [ground]
{Anvil} [ground]
{Fire}
[NAME:Iron Helm]
[SUBMENU_END:Clothing]