Abstract: The machine comprises a guideway 12 extending past a series of work stations 13, 13' and supporting a series of pairs of pallets 14, 14' carrying connectors 15, 15'. A return guideway 16 supporting empty, returning pallets extends under the guideway 12. Forward and return pallet indexing mechanisms 17 and 17' are carried by pallet lifts 18 and 18' movable between entry and exit ends of the respective upper and lower guideways (12, 16) to carry pallets (14, 14') between the guideways and to enable the indexing mechanism 17 and 17' to feed the pallets alternately onto the entry ends of the upper and lower guideways and receive expelled pallets (14, 14') from the exit ends thereof. Pilot mechanisms 21, 21' are arranged for vertical reciprocation into engagement with leading and trailing pallets (14, 14') on the upper and lower guideways (12, 16) alternately to confine the pallets (14, 14') together on the guideways (12, 16) in between operation of the forward and return indexing mechanisms 17 and 17'.