Mamiya 6 75mm and 50mm Lenses: Stiff Focus from Hardened Grease
Originally posted on Instagram. Notes from the repair bench, kept here as a searchable archive. View the original on Instagram
A common request that I get is for service to the Mamiya 6 75mm and 50mm lenses with stiff focus. For some reason, these two lenses are the ones that get stiff focus issues, seems like when the Mamiya 7 was introduced, Mamiya used a different lubricant on the helical threads and solved the lubrication issue. The lubricant used on the Mamiya 6 lenses was Kahata 3D and from my records, this was only used on the Mamiya 6 lenses and the 645 55-110mm zoom lens.
Usually these lenses present with either rough focus, uneven focus ring movement or a barely moveable focus ring. Generally, if the focus is just a bit stiff but usable, it is best to continue using the lens as-is. Because, the solution to the issue is a complete disassembly of the lens which includes removing the shutter, flex cable and the other lens barrel parts. And then taking the helicals apart to remove all traces of old lubricant and install new. This all takes a lot of time to do properly and recalibrate focus and rangefinder. So it is a bit costly.
The Mamiya 75mm lens in the first photo arrived with an erratic focus and dry spots, usable but annoying. Photo three shows the helicoid taken apart and visible is the orange grease which has hardened.
The last image, a video, shows the lens reassembled and a smooth focus.
