February 28, 2014 by firstname.lastname@example.org
Universal and wobble joints can save your sanity, and the skin on your knuckles, when the fastener you are trying to access is in a weird location.
Universal and wobble joints are flexible joints that allow you to use a socket with a ratchet, breaker bar, or extension, when a nut or bolt is accessible, but there is limited clearance around it. We discussed flexible joints briefly in Wrenches and sockets. Flexible joints are great additions to any tool box and can help reduce time and frustration when working on your car.
Ratchets and sockets are a very efficient means for removing and installing fasteners. If these fasteners are obstructed by surrounding components so you can’t use a ratchet and socket, needing to use a regular wrench can add a lot of time when performing a job. In some cases there isn’t room for a wrench either, so what can you do? A universal or wobble joint might be the solution.
The wobble joint looks like a short socket extension with the edges rounded on the male end. These rounded edges allow the wobble joint to tilt inside the female recess of a socket, so that you can position your ratchet or extension slightly off center. Wobble joints are quite stable and transmit forces reasonably and predictably to a fastener.
A universal joint allows you to get your ratchet or extension pretty far off center to turn a fastener. Universal joints are very unstable, due to their extreme flexibility. They also do not turn evenly and transmit forces to a fastener in an unpredictable fashion.
Universal joints are slightly longer then wobble joints, limiting where they can fit. Use a wobble joint instead of a universal joint, when you can, as the wobble joint is a lot more stable, reducing the risk of fouling a fastener. Flexible joints, especially universal joints, are also notorious for breaking spark plugs, so extra care needs to be taken when using a flexible joint to remove or install a spark plug.
Note: Use care and patience when using a flexible joint. These tools, especially universal joints, have a tendency to pull to the sides when you apply torque and slip off the fastener head. This slippage can foul the head of the fastener, making it impossible to loosen the fastener with a wrench or socket (this is really bad). Remember that flexible joints (and extensions) will change your torque measurements, so don’t ever use them with a torque wrench.
The key to success when using a flexible joint, or any long socket extension, is applying enough force onto the back of the socket, so that it remains fully seated on the fastener. With flexible joints, his takes practice.
- If you can get one hand onto the back of the socket to stabilize it, near where the flexible joint connects to the socket, that is optimal – be careful not to get pinched by the moving parts of the flexible joint,
- Grasping the ratchet head and keeping it stable while turing the handle is also effective in stabilizing a flexible joint.
Wobble and universal joints are available in all of the most popular drive sizes (1/4-inch, 3/8-inch, 1/2-inch). When you get into larger drive sizes past this point, flexible-joint options start to become limited due to the more extreme levels of torque that are needed with the larger drive sizes.
You can purchase sockets with universal or wobble joints already built in. These tools will be shorter in length than using one of the flexible joints, described above, with a standard socket, giving you more opportunities to use them. Sockets with built-in flexible joints are quite expensive: I’ve only seen them in the tool boxes of professional mechanics, where time is money and the cost can be justified.