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Looking at TMW llc's excellent repairs shown in "The power of Hydraulics!!! thread, I started wondering about the pins and bushings frequently used in hydraulic powered equipment. I was hoping those of you with real world, field hydraulic equipment, repair experience could enlighten me.I have seen the various arguments that pins should be harder than the bushings and that bushings should be harder than the pins depending on how the connection is constructed and maintained.What material is typically used for welded in bushings and why? Machinability, Ease of Welding, Durability? What are the trade offs to make in material selection? Same question for the pins?How much pin/bushing clearance should be provided for adequate grease to lube the joint? 0.005" to ? How tight or loose should this clearance practically be?What is the best way to keep grease in the joint?I have seen various combinations of zerk fittings, grooves, or via holes in the bushing or pin to promote flow of fresh grease into the pin/bushing contact points for lubrication. How are these grooves or vias sized so that the strength of the pin or bushing are not compromised? How well do this grooves or vias get grease to the contact surfaces between the pin and bushing?What recommendations do you have for designing a pin/bushing joint that is robust, easily maintained, and field repairable?farmersam, irish fixit, forhire, zapster, TMW llc any thoughts on the subject?Thanks for any and all comments. Your assistance is very much appreciated.Regards
Reply:Thanks man! As far as i know there is no set standard for these materials. I have seen all kinds of different types used. These are a few that i have seen before ,4140,4140,8620,1045,1050,1095,Also induction hardened materials like chrome are sometimes used. I don't begin to know the differences in them, this is where the expert comes in. For me thats the manufacturer. I use OEM for everything and if its not available or I cant find the info then its time to get an engineer involved. The customer would be heavily involved at this point as well. If the wrong materials or specs are used everything might look and work fine then 5 hrs later all hell breaks loose. I have seen bushings wear in a day because the wrong materials where used. Good for me if they need to be replaced. As long as We install the correct ones. As far as tolerance goes?.005 is pretty common. There is also allot more than I claim to know that goes into this as well. As far as engineering is concerned. .This was brought up before and I saved this link. It had some good answers to the same questions http://www.practicalmachinist.com/vb...loader-171474/Hope that helps a bit.
Reply:Amilleruser , take a look at cat stuff I used to work in a job shop and we did allot of repairs on cat buckets" That stuff is built to last " One thing i remember about the cat bushings is they always had grease grooves machined in them and no one else did.that being said they are Mighty proud of they're stuff. Take a look at some of they're stuff to get some ideas . grease the bushing instead of doing it through the pin.if you can buy off the shelf stuff so when you need to repair it you can easily they make grease seals that you can put on the ends of each bushing like a rotor in a car . Make everything from common size materials the chrome rod you mentioned for hyd. cylinders works good for grease pins once you get underneath the chrome it welds and machines pretty good .Are you building or repairing ?what exactly are you doing ?it sounds interesting . good luck and keep us posted . CT
Reply:Most bushings I encounter are pressed In not welded and the pin is usually harder than the bushing unless the parts arnt OE quality as TMW stated
Reply:I cant speak much of heavy equipment, but us millwrights go by the general rule that the more easily replaced part should be of the softer material.... |
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发表于 2021-8-31 22:37:47