Thank you for allowing me to join this group! ? This is my first post. ?

I own a Clark Metalworker 4x6 and have used it in my hobbies for many years. ?The bearings in the gearbox have finally worn out and I’ve removed both shafts and pressed the old bearings off, and have acquired new bearings and seals from McMaster. I’ve now pressed the new bearings; spacers and seals onto the shafts and am ready to press the assemblies back into the housing. ?

My question is what is the best procedure for pressing these assemblies into the housing while obtaining the correct spacing between the gears? ?I’m accustomed to pressing bearing races into a bore up against to shoulder that would ultimately determine the final positioning of the assembled unit. ?I regret not obtaining a micrometer measurement of the shaft positions in relation to the casting prior to disassembly. ??

Perhaps I’m over thinking this? ?Any advice would be appreciated. ?

Thank you. ?

开云体育

Hi Michael/Ralph

Michael, I understand your concern about the bearing spacing and position but think it’s probably not too much of an issue, as most things can be adjusted.? The position of the shafts in their bearings affects the clearance between the worm and brass gear and the end position of the output shaft determines where the drive band-wheel sits, so affects the tracking of the blade.

I’ve never removed my gearbox input shaft but have had to change the bearings on the output shaft.? I removed them the same way Bill did.? The bearings are a tighter fit in the casting than on the shaft, so I drew the new ones into the heated casting with a bit of all-thread and thick washers, so they were flush both sides, then tapped the shaft back through. I can’t remember which side I re-fitted the shaft from but think I might have mounted the brass gear before doing so, as it would have been easier to pin the gear to the shaft that way. Seem to recall the pin hole wasn’t on centre, so the gear only fitted one way. ?

The curve of the brass gear’s teeth should be central over the worm, when the boss of the brass gear just touches the bearing inner race.? This is because the drive band-wheel is located in its proper position by a spacer (#11 in the diagram in the Clarke Metalworker manual that’s in the files section ) between the inner face of the drive band-wheel’s boss and the adjacent bearing inner race, when the inner face of the brass gear is against the other bearing’s inner race. If the brass gear isn’t against that inner bearing the output shaft could float axially through the bearings and the drive band-wheel wouldn’t be in the right position to track the blade properly. ?

If your brass gear is not centralized over the worm in this position, then the output shaft bearing at the inner face of the gearbox needs to either be pressed in further, or you space the gear off the bearing with shim washers. The length of spacer #11 can be changed to suit if needs be.

Actually, to get everything in the right position you need to mount the gearbox input shaft first, as the axial position of the worm, in the direction of the input shaft, needs to be aligned centrally about the output shaft’s centre first. Again, I think you are better to pull the bearings into the casting first, rather than assemble the bearings on the shaft and press the unit in. On my saw, both bearings on the input shaft are flush with the edges of the casting as delivered from the factory. There are no steps or lands to position the shaft, that I know of, it’s just maintained in position by friction of the shaft in the bearings.

The reason to fit the bearings to the casting first, is that the area of contact between the bearing outer race and the casting is much bigger than the contact area between the shaft and the inner race.? Even if the fit is the same on both sides of the bearing, you need a lot more force the fit the bearings to the casting than the shaft to the bearings.? If fitted as a unit the bearings will slide on the shaft, especially as there are no lands on the shaft to keep the bearings and seal in position, unless you put spacers in between the bearing’s and seal’s outer races. Putting spacers in is probably best engineering practice, but these saws were not made that way initially, and the loads on the bearings are not high, so the bearings last ok after tapping the shaft through.

Last of all remount the blade, tension it and then run the saw.? The back of the blade should just NOT touch the rim on the band-wheel (~0.020” (0.5mm) clearance is good).? Shift the band-wheel on its shaft to get this clearance and either reduce or lengthen the #11 spacer to suit (5/8”ID ?plastic electrical conduit or washers makes good spacer material).? Rgds - jv