Fork arms carry the entire load and are checked by eye far more often than by caliper. They wear slowly and they fail suddenly, and a pair that looks perfectly serviceable from the driver's seat can already be past the point at which the inspection standard says it should have been withdrawn. This guide covers how forks are specified, the measurements that condemn them, and what our team needs in order to quote a replacement pair.
How a fork arm is specified
Four things identify a fork: the length, width and thickness of the blade, and how it mounts to the carriage. Length and width are read straight off the blade. Thickness must be measured on the shank, well above the heel, where the fork has never been in contact with a load or the floor. Mounting is either hook type, where the fork hangs on the carriage bars, or shaft type on older and heavier trucks. For hook forks, record the carriage class as well: measure the vertical distance between the upper and lower carriage bars, because Class II, III and IV forks are not interchangeable even when the blade dimensions match.
The ten per cent rule
The most important measurement is blade thickness at the heel, the bend where the blade meets the shank and where load concentrates. Take a caliper reading there and compare it against the shank higher up, which sees almost no wear. Under the ISO 5057 inspection standard, once the heel has lost ten per cent of its original thickness the fork must be taken out of service. That figure sounds small, but strength falls away faster than material does, and the truck's rated capacity is no longer valid. Worn forks are not to be built back up by welding in the workshop.
What else condemns a pair
Cracks anywhere — most often at the heel or around the hook welds — condemn a fork outright, with no wear allowance at all. So does a blade-to-shank angle that has opened up more than three degrees from its original ninety, which shows the fork has been overloaded and bent. With both forks hung on the carriage, compare the tip heights: a difference of more than three per cent of blade length means the pair no longer sits level. Then check the hooks for wear and elongation, the positioning latch for a worn or missing pin, and the stamped marking — a fork whose capacity marking is no longer legible cannot be verified and should be replaced.
Inspect yearly, replace in pairs
The standard calls for fork arms to be inspected at least once every twelve months, and more frequently on trucks running multiple shifts, handling abrasive loads or working across rough yards. When the time comes, replace forks as a matched pair. Fitting one new fork alongside a worn one leaves the driver with two blades at different heights and different remaining strength, and loads the carriage unevenly. Renew the latches and pins at the same time; they are what keeps the forks where they were set.
What to send us for a quote
The fastest route to a correct quote is the truck's make, model and serial number, the blade length, width and measured heel thickness from the old fork, the mount type, and a photo of the fork on the carriage showing the hooks. Include the capacity marking if it is still readable. We supply fork arms, fork pin and latch kits and carriage hardware for TOYOTA, LINDE, STILL, HYSTER, JUNGHEINRICH, KOMATSU, MITSUBISHI and TCM trucks, along with universal-fit equivalents where the dimensions and carriage class match. Send the details through our quote form and we will confirm what fits.
