Replacing the lower pins on my bob-batch quick attach plate-to-arm - they are 1.5" nominal diameter and 1.25" long axially. When I got the replacements, the I.D. of the bushing is 1.500" but the O.D. of the pin is 1.475. So that's 0.025" diametral clearance. That's plenty to click and visibly rock and click back and forth. It felt to me like these should be a close slip fit with barely detectable rocking/slop. But I dont have much first hand heavy equipment experience. The seller was very quick to respond - checked inventory and confirmed same diameter and offered immediate RMA/shipping but they didn't specifically confirm or disagree with me thinking it was too loose though - so could just be 'customer always right' policy. So just wondered if anyone could confirm I'm on the right track here before I waste time ordering somewhere else or OEM$$.
Yep, nope! When I go to the trouble of replacing pins and bushings, they better be tighter than that. My skid steer quick attach pins,I made myself and ordered some bushings from McMaster and I had 1/2 a thou. I had to polish the inside of the bushings and the outside of the pins, to get them in. Planning on doing the bottoms, this winter and will have to cut the welded boss off and will do the same. Will make them greasable also.
What's the machine? I had a similar problem with OEM parts for my Bobcat excavator. I contacted the dealer about it and they got a CAD drawing from Bobcat of the pin and bushing and it showed that the parts were within spec. Bobcat actually designed them that loose. It may be the same situation with yours.
Yeah that was my thought - all this trouble to start off that loose?!? One side is wallowed with no bushing - and the new bushing in the wallowed hole is literally tighter than the pin to the bushing (it's not badly wallowed - just barely). This is an 843 with the bob-tach with the single center piston - these are the lower pins to the loader arms. That is my worry - that I'm expecting too much and that's just how they make them. I know when both are assembled, it won't rock like an individual one will of course since there's 2 of them 4 ft apart - but it will still be little bangs vs just smooth rotating which can't be good for long term wear.
Many occasions the focus is the new pin to the new bushing clearance - but more often than not the bushing od bedding (machine bore) is no way concentric / parallel to the other bushing because the machine's bore is yielded and or worn from working the machine. For these real world occasions having some tolerance decreases the odds for what is about to be reported next. We knew a fitter and he preferred to make his own parts (to save money) so he made new bushings and pins .... never did learn (1) if he line bored the fitment on the machine nor (2) the alloy chosen but what we do know he made them w very little clearance. There he was, soon after the replacement, happily working away with the new parts and fresh grease and the excessively small clearance did a thing called "galling" and no amount of force could move the joint. His only solution was the carbon arc and then a weld out and line bore - and then he installed the OEM bushings and pins. Let good judgement be one's guide on these aspects of machinery.
You make a good point - especially with DIY repairs - weld in bushings, deformation, etc... doesn't take much to put the two sides out of parallel or concentricity... and with real close clearances, you could see some pretty high internal loads - galling at worst - at least difficulty assembling. Now I'm thinking maybe just give them a try. It's not a very hard job now I know how they come apart (and where to hit with the sledge hammer), and these aftermarket one are both bushings and both pins for the less than the price of one bobcat pin ($100) - which could be the same diameter anyway as far as I know anyway. And it will be a 90% improvement over the worn pins and bushing being replaced anyway.