The shaft is the backbone of the torsion spring system: it carries the springs, connects the two cable drums, and transmits the rotation that winds the cables. It is rarely thought about, as it remains hidden under the garage ceiling. Yet, a bent, worn, or poorly suited shaft causes jerky movement, a crooked door, and premature wear of parts.
This article explains the difference between a hollow shaft and a solid shaft, the role of keyways, bearings, and couplings, and helps you prepare a reliable order. It is part of our series on the lifting system.
The role of the shaft in the lifting system
The shaft is a horizontal axle installed above the door, supported by bearings fixed to the lintel. The torsion springs are threaded around it, and the drums are fixed to its ends. When the door goes down, the shaft turns and twists the springs; when it rises, it turns in the opposite direction.
It must therefore be perfectly straight, of a suitable diameter, and rigid enough to transmit the force without flexing. On most residential doors, you will find a 25.4 mm (1-inch) shaft. This is the size we offer in both hollow and solid versions. If you are unsure about the diameter, measure it with a caliper at a non-worn point.
Hollow shaft or solid shaft: the differences
The hollow shaft is a tube: it is lighter and easier to handle. The solid shaft with groove is a solid bar designed to receive a key in a machined slot. The choice depends first on what is installed on your door: as a rule, you replace it with an identical part to maintain compatibility with the drums, springs, and accessories.
Both of our shafts are sold by the meter: you order the length you need. To calculate it, measure the existing shaft from one end to the other, or, if it is missing, the width of the door plus the necessary margin for the bearings and drums. Add a small reserve and adjust the cut during installation.
Keys: a small essential part
The key is a metal wedge that secures a rotating element to the shaft: it prevents the drum or spring from slipping. On a solid shaft, a straight key is used; on a hollow shaft, a bent key. Our references: the 6.35 x 6.35 x 100 mm key for solid shaft and the 9.53 x 6.35 x 96 mm bent key for hollow shaft.
A worn, deformed, or missing key creates play and misaligns the door adjustment. If you replace the shaft, systematically replace the keys: they cost little and are essential to the reliability of the system. Before ordering, make sure the type of key corresponds to your shaft, whether hollow or solid.
Bearings and couplings: supporting the shaft properly
Bearings hold the shaft in rotation. There are intermediate bearings, placed in the center to support large widths, and end bearings. We offer the 67 mm intermediate bearing and the 86 mm intermediate or end bearing. Compare their dimensions with those of your current bearings.
When the shaft is made up of two sections, they are joined with a 25.4 mm shaft coupling. This accessory also allows for repairing a shaft without replacing it entirely when the configuration permits. In all cases, worn bearings that squeak or overheat must be replaced at the same time as the shaft to avoid premature wear.
Replacing the shaft: precautions and sequence of operations
Replacing the shaft involves releasing the spring tension, removing the drums, and detaching the cables. This is a high-risk operation: a non-relaxed torsion spring can cause serious injury. It should be performed with the appropriate tools, such as our spring tensioning bar, and with the door immobilized in a safe position. If in doubt, entrust the work to a professional.
Once the new shaft is in place, reassemble the bearings, springs, drums, and cables in this order, check the alignment of the entire assembly, and adjust the tension. Follow the instructions in our spring guide for tensioning, then test the balance with the motor disengaged.
Conclusion
Whether hollow or solid, the shaft must match your installation: diameter, length, keys, and bearings form a significant assembly. Replacing with an identical part remains the rule, while renewing small wear parts along the way.
Our shafts are sold by the meter to adapt to each door width. If you have any doubt about the correct configuration, send us a photo of your shaft and its ends.
FAQ: sectional door shaft
Which shaft diameter should I choose?
On most residential doors, the shaft measures 25.4 mm. However, check the diameter of your existing shaft before ordering.
What shaft length should I order?
Measure the existing shaft, or take the door width plus the margin for bearings and drums. Shafts are sold by the meter.
Should the keys be changed with the shaft?
Yes, it is recommended. They are inexpensive and their wear creates play that disrupts adjustment.
Can I replace the shaft alone?
This requires releasing the spring tension and dismantling the entire assembly. This operation is dangerous: call a professional if you are not comfortable.