Martin 4012COV Aluminum Coupling Cover is the protective cover for a Martin chain coupling — it bolts around the hubs and chain to retain lubricating grease, sold separately for maintenance replacement.
A chain coupling connects two shaft hubs, each machined with sprocket teeth, using a double-strand roller chain that meshes with both hubs’ sprockets and wraps around the connection. Torque transfers from the driving hub through the chain’s rollers into the driven hub. The chain’s own clearance between rollers and sprocket teeth gives the coupling a small amount of built-in flexibility, letting it absorb shock and tolerate minor misalignment without the added cost or complexity of a molded elastomeric insert. A two-piece cover, bolted around the hubs, retains the grease the chain needs to run without excess wear — chain couplings, unlike jaw or Quadraflex designs, need periodic lubrication.
Confirm bore size and keyway on both the driving and driven hub — like other coupling types, chain couplings are typically sold as a hub pair plus chain and cover, and each side can have a different bore for dissimilar shaft sizes. Match the coupling’s size number to the sprocket pitch and chain strand count; chain, cover, and hubs from a given size aren’t interchangeable with a different size even if bores happen to overlap. Check the torque rating against your application’s peak load, and factor in that the chain needs periodic greasing to avoid premature wear — this is routine maintenance a jaw or Quadraflex coupling doesn’t need. If you’re replacing just the cover or the chain rather than the full assembly, match the exact size number stamped on your existing hub.
Chain couplings are used across general industrial power transmission — conveyors, packaging equipment, mixers, fans, and pumps — anywhere a simple, low-cost coupling is preferred over the higher torsional stiffness of a grid coupling or the maintenance-free operation of a jaw or Quadraflex design. They’re a common OEM choice on lower-speed, lower-precision machinery where upfront cost matters more than eliminating lubrication intervals.
This is Martin’s 4012COV size chain coupling component. Chains, covers, and hubs are sized together — check the exact size number stamped on your existing hardware before ordering a replacement part, rather than assuming bore size alone is enough to confirm a match.
