There are many misunderstandings about grease guns. According to grease gun manufacturers:
- The pressure generated by hand-powered grease guns, for the most part, is dependent on the strength of the person operating it. “It takes a strong guy to produce 5,000 psi with a normal grease gun,” says Keith Rohan with SKF (manufacturer of Lincoln-brand grease guns).
- The latest generation of battery-powered grease guns can produce up to 10,000 psi. Rohan says 7,500 psi is generally adequate for farm use. “Ten thousand psi sounds good, but can push grease into places where it shouldn’t be,” he adds.
- If a grease gun is rated to 10,000 psi, beware when replacing the hose. Replacement hoses from auto parts stores are often rated to only 5,000 psi.
- Some battery-powered grease guns offers two speeds. On Milwaukee-brand cordless grease guns, “low speed” produces up to 10,000 psi, but pumps less grease per “stroke.” Their “high speed” setting puts out 5,000 psi, but moves a greater volume of grease per stroke.
- Cordless grease guns may advertise “gear drive,” but not explain if those gears are plastic or metal. “Metal” gears may be made of relatively brittle cast iron. While some high-quality plastic gears are actually stronger than cast iron gears, the toughest grease gun gears are made from machined steel. They’re also the most expensive.
Over the years, I’ve learned a few tips and tricks as well about grease guns and grease. Here are a couple that come to mind:
- It’s best to store grease tubes vertically. I once stored a carton of grease tubes horizontally on a shelf. I had intermittent problems with “air locking” the grease gun, especially in cool or cold weather. When I started storing the grease tubes vertically, the air-locking problem went away. My theory is that storing the tubes sideways allowed the grease to settle to the “bottom” of the tube, creating a channel of air at the top of the tube. When I jammed the tube into a grease gun and rammed the spring-loaded follower home, it captured air bubbles in the grease. Beyond that theory, I never thought about it anymore because storing the grease tubes vertically seemed to solve the problem.
- Ever buy a new grease gun and have trouble getting it to pump consistently for the first few tubes of grease? I learned from a grease gun manufacturer that it’s good to smear some grease around the inside of the tube on the grease gun that holds the cartridge of grease. The coating of grease helps seal the tube against air leaks. Notice that when you pull a used grease cartridge out of an old gun, there’s a “suction” that slightly resists removing the cartridge? A new grease gun won’t work well until it has that coating of grease on the inside of the barrel to create similar suction.
