Attaching gears to
shafts with Trib-Joins
Trib-joins give the
strength of a weld made with the convenience of a press fit.
They increase press fit strength by up to four and more than
double the strength of shrink fit joins and thereby offer ways
of improving gear box design by the selective use of high
Trib-Tools dispense trace amounts of a chemical Cold Welding Agent which when placed between two rubbing steel surfaces held in close contact causes a rapid increase in friction to a point where widespread solid phase cold welding occurs after as little as 2mm of rubbing. The process will join all steels both hard to hard and hard to soft, but it will not join bronze, brass, copper, zinc or flake cast iron to steel. Typical uses are shown below for securing a wide range of gear sizes to shafts:
Fig 1 shows a small gear mounted on the end of a shaft, such as f.h.p. or power tool drive. The parts are machined to ISO H7/p6 pre-fit. The gear is first forced part way on dry to establish alignment, then the remaining exposed join areas are treated with a Trib-Tool before the gear is forced into its final position. If the gear can be pushed past it final position before treating, then pulled back against the shaft end this restricts the assembly forces to the shaft end.
Fig 2 shows a medium size gear typical of a reduction drive or automotive transmission. These are best heat shrunk onto shafts treated with a Trib-Tool. This will more than double the join strength. If after assembly induction currents are selectively driven across the join with induction coils the join strength increases as more welding occurs due to diffusion bonding.
Fig 3 shows a very large gear. Here it is best to cut a shallow spiral into the shaft and then position the gear onto the shaft by cooling the shaft or warming the gear before pressing it into position. The Cold Welding Agent is then injected into the grove and the gear rotated slightly (only a few degrees) sufficient to carry the Cold Welding Agent into the rubbing contact area where the welding occurs. The rotation may be conveniently affected after final assembly of the shaft into the equipment while this under goes final tests.
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