How to weld tools that won't break?

Lately I've been trying to weld tools with small parts. When first equip the tool everything is fine and in place but when unequipped small parts are scattered everywhere and most of the welds break(some of them are still in place though).

I'm using this script to do the welding:

function weld()
	local parts,last = {}
	local function scan(parent)
		for _,v in pairs(parent:GetChildren()) do
			if (v:IsA("BasePart")) then
				if (last) then
					local w = Instance.new("Weld")
					w.Name = ("%s_Weld"):format(v.Name)
					w.Part0,w.Part1 = last,v
					w.C0 = last.CFrame:inverse()
					w.C1 = v.CFrame:inverse()
					w.Parent = last
				end
				last = v
				table.insert(parts,v)
			end
			scan(v)
		end
	end
	scan(script.Parent)
	for _,v in pairs(parts) do
		v.Anchored = false
	end
end

weld()