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General Bobcat Skidsteer Forum
453 Bobtach pins and bushings
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<blockquote data-quote="OldMachinist" data-source="post: 12265" data-attributes="member: 437"><p><span style="font-family: 'Times New Roman'">A couple of weeks ago I decided it was time to replace the pins that hold the Bobtach to the lift arms. As you see they where pretty worn compared to the new on in the middle.</span></p><p><span style="font-family: 'Times New Roman'"><a href="https://www.skidsteerforum.com/DesktopDefault.aspx?tabid=52&gallerypage=1&currentitem=2&path=OldMachinist" target="_blank"><img src="https://www.skidsteerforum.com/Portals/57ad7180-c5e7-49f5-b282-c6475cdb7ee7/TTTGallery/OldMachinist/_thumbs/DSCF0172.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></a></span></p><p><span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">On my 453F there are no factory installed pressed in bushings. The service manual says if the hole wears out you have to cut the old welded on bushings off and weld new ones on in the right location. I really didn't like the idea of trying to get things all lined up by welding in new bushings so this what I came up with.</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p> <span style="font-family: 'Times New Roman'">I decided I would like to bore out the hole on the old bushings and fit them with replaceable bronze bushings. The alloy 932(SAE660) bronze bushings I used have plenty of load capacity (4,000 psi) for this machine but for larger machines you could step up to alloy 954(4,500 psi) or you could make steel ones. I used bronze because most of the future wear would be in the bushing ($2 each from McMaster Carr) and not on the pins ($35 each from BobCat) and changing the bushings as needed would be simple.</span></p><p><span style="font-family: 'Times New Roman'"><a href="https://www.skidsteerforum.com/DesktopDefault.aspx?tabid=52&gallerypage=1&currentitem=0&path=OldMachinist" target="_blank"><img src="https://www.skidsteerforum.com/Portals/57ad7180-c5e7-49f5-b282-c6475cdb7ee7/TTTGallery/OldMachinist/_thumbs/bushing.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></a></span></p><p><span style="font-family: 'Times New Roman'">Now I could have taken the Bobtach into the machine shop I retired from on a weekend and done this real simple but having time on my hand I wanted to figure out a way a person with some tools available could do this at home. I checked the original welded in bushings and found they where made from cold rolled stock and that the bores were concentric with the outside diameter. I made two guide bushings from 4140 steel on the lathe that slide over the outside diameter and drilled and tapped three setscrew holes to lock them on. I bored them to be a slight press fit so that I could tap them on and off with a lead hammer. As you can see I notched them out to slip down past the gussets. My pins are 1" in diameter so the first bushing has a 1 1/16" bore and the second has a 1 1/8" bore.</span></p><p><span style="font-family: 'Times New Roman'"><a href="https://www.skidsteerforum.com/DesktopDefault.aspx?tabid=52&gallerypage=1&currentitem=4&path=OldMachinist" target="_blank"><img src="https://www.skidsteerforum.com/Portals/57ad7180-c5e7-49f5-b282-c6475cdb7ee7/TTTGallery/OldMachinist/_thumbs/guides.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></a></span></p><p><span style="font-family: 'Times New Roman'"><a href="https://www.skidsteerforum.com/DesktopDefault.aspx?tabid=52&gallerypage=1&currentitem=3&path=OldMachinist" target="_blank"><img src="https://www.skidsteerforum.com/Portals/57ad7180-c5e7-49f5-b282-c6475cdb7ee7/TTTGallery/OldMachinist/_thumbs/guideinatalled.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></a></span></p><p><span style="font-family: 'Times New Roman'">I used my bucket as a fixture to hold the Bobtach and magnetic drill square to each other. The bucket was shimmed level and then I placed small welds to hold the Bobtach in place after it was lined up. I used a 1 1/16" shell reamer first then changed the guide bushing and finished the hole with a 1 1/8" reamer. Then I ground the welds off flipped the Bobtach 180 deg. and did the other side. The reamers and arbor cost me about $125. The new bores ended up being concentric with the outside diameter within .005" and right on size for a press fit for my bushings.</span></p><p><span style="font-family: 'Times New Roman'"><a href="https://www.skidsteerforum.com/DesktopDefault.aspx?tabid=52&gallerypage=1&currentitem=6&path=OldMachinist" target="_blank"><img src="https://www.skidsteerforum.com/Portals/57ad7180-c5e7-49f5-b282-c6475cdb7ee7/TTTGallery/OldMachinist/_thumbs/setup1.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></a></span></p><p><span style="font-family: 'Times New Roman'"><a href="https://www.skidsteerforum.com/DesktopDefault.aspx?tabid=52&gallerypage=1&currentitem=7&path=OldMachinist" target="_blank"><img src="https://www.skidsteerforum.com/Portals/57ad7180-c5e7-49f5-b282-c6475cdb7ee7/TTTGallery/OldMachinist/_thumbs/setup2.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></a></span></p><p><span style="font-family: 'Times New Roman'"><a href="https://www.skidsteerforum.com/DesktopDefault.aspx?tabid=52&gallerypage=1&currentitem=1&path=OldMachinist" target="_blank"><img src="https://www.skidsteerforum.com/Portals/57ad7180-c5e7-49f5-b282-c6475cdb7ee7/TTTGallery/OldMachinist/_thumbs/bushinginstalled.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></a></span></p><p><span style="font-family: 'Times New Roman'"><span style="font-family: 'Times New Roman'">I also reamed out the welded in tilt cylinder bushings on the Bobtach and both ends on the tilt cylinder while I was at it. Now all they all have replaceable bushings</span></span></p><p><span style="font-family: 'Times New Roman'"><span style="font-family: 'Times New Roman'"><a href="https://www.skidsteerforum.com/DesktopDefault.aspx?tabid=52&gallerypage=1&currentitem=8&path=OldMachinist" target="_blank"><img src="https://www.skidsteerforum.com/Portals/57ad7180-c5e7-49f5-b282-c6475cdb7ee7/TTTGallery/OldMachinist/_thumbs/tiltbushings.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></a></span></span></p><p><span style="font-family: 'Times New Roman'"><span style="font-family: 'Times New Roman'"></span></span></p><p><span style="font-family: 'Times New Roman'"><span style="font-family: 'Times New Roman'">I ran a small brake cylinder hone in the tapered pinholes on the lift arms to make sure the pins would seat proper. These holes had no wear just a little rust but on any tapered mount hole must be clean for it not to start working around and get loose. I used delrin washers I also bought from McMaster Carr to take out some of the side play of the Bobtach. When I reassembled it every lined up perfectly.</span></span></p><p> <span style="font-family: 'Times New Roman'"><span style="font-family: 'Times New Roman'"></span></span></p><p><span style="font-family: 'Times New Roman'"><span style="font-family: 'Times New Roman'">All together I spent about $250 and it took 6 hrs. which included making the bushings. In the future I figure it will take me no more than 1 hour to replace the bushings.</span></span></p><p> <span style="font-family: 'Times New Roman'"></span></p></blockquote><p></p>
[QUOTE="OldMachinist, post: 12265, member: 437"] [FONT=Times New Roman]A couple of weeks ago I decided it was time to replace the pins that hold the Bobtach to the lift arms. As you see they where pretty worn compared to the new on in the middle. [URL='https://www.skidsteerforum.com/DesktopDefault.aspx?tabid=52&gallerypage=1¤titem=2&path=OldMachinist'][IMG]https://www.skidsteerforum.com/Portals/57ad7180-c5e7-49f5-b282-c6475cdb7ee7/TTTGallery/OldMachinist/_thumbs/DSCF0172.jpg[/IMG][/URL] On my 453F there are no factory installed pressed in bushings. The service manual says if the hole wears out you have to cut the old welded on bushings off and weld new ones on in the right location. I really didn’t like the idea of trying to get things all lined up by welding in new bushings so this what I came up with. I decided I would like to bore out the hole on the old bushings and fit them with replaceable bronze bushings. The alloy 932(SAE660) bronze bushings I used have plenty of load capacity (4,000 psi) for this machine but for larger machines you could step up to alloy 954(4,500 psi) or you could make steel ones. I used bronze because most of the future wear would be in the bushing ($2 each from McMaster Carr) and not on the pins ($35 each from BobCat) and changing the bushings as needed would be simple. [URL='https://www.skidsteerforum.com/DesktopDefault.aspx?tabid=52&gallerypage=1¤titem=0&path=OldMachinist'][IMG]https://www.skidsteerforum.com/Portals/57ad7180-c5e7-49f5-b282-c6475cdb7ee7/TTTGallery/OldMachinist/_thumbs/bushing.jpg[/IMG][/URL] Now I could have taken the Bobtach into the machine shop I retired from on a weekend and done this real simple but having time on my hand I wanted to figure out a way a person with some tools available could do this at home. I checked the original welded in bushings and found they where made from cold rolled stock and that the bores were concentric with the outside diameter. I made two guide bushings from 4140 steel on the lathe that slide over the outside diameter and drilled and tapped three setscrew holes to lock them on. I bored them to be a slight press fit so that I could tap them on and off with a lead hammer. As you can see I notched them out to slip down past the gussets. My pins are 1” in diameter so the first bushing has a 1 1/16” bore and the second has a 1 1/8” bore. [URL='https://www.skidsteerforum.com/DesktopDefault.aspx?tabid=52&gallerypage=1¤titem=4&path=OldMachinist'][IMG]https://www.skidsteerforum.com/Portals/57ad7180-c5e7-49f5-b282-c6475cdb7ee7/TTTGallery/OldMachinist/_thumbs/guides.jpg[/IMG][/URL] [URL='https://www.skidsteerforum.com/DesktopDefault.aspx?tabid=52&gallerypage=1¤titem=3&path=OldMachinist'][IMG]https://www.skidsteerforum.com/Portals/57ad7180-c5e7-49f5-b282-c6475cdb7ee7/TTTGallery/OldMachinist/_thumbs/guideinatalled.jpg[/IMG][/URL] I used my bucket as a fixture to hold the Bobtach and magnetic drill square to each other. The bucket was shimmed level and then I placed small welds to hold the Bobtach in place after it was lined up. I used a 1 1/16” shell reamer first then changed the guide bushing and finished the hole with a 1 1/8” reamer. Then I ground the welds off flipped the Bobtach 180 deg. and did the other side. The reamers and arbor cost me about $125. The new bores ended up being concentric with the outside diameter within .005” and right on size for a press fit for my bushings. [URL='https://www.skidsteerforum.com/DesktopDefault.aspx?tabid=52&gallerypage=1¤titem=6&path=OldMachinist'][IMG]https://www.skidsteerforum.com/Portals/57ad7180-c5e7-49f5-b282-c6475cdb7ee7/TTTGallery/OldMachinist/_thumbs/setup1.jpg[/IMG][/URL] [URL='https://www.skidsteerforum.com/DesktopDefault.aspx?tabid=52&gallerypage=1¤titem=7&path=OldMachinist'][IMG]https://www.skidsteerforum.com/Portals/57ad7180-c5e7-49f5-b282-c6475cdb7ee7/TTTGallery/OldMachinist/_thumbs/setup2.jpg[/IMG][/URL] [URL='https://www.skidsteerforum.com/DesktopDefault.aspx?tabid=52&gallerypage=1¤titem=1&path=OldMachinist'][IMG]https://www.skidsteerforum.com/Portals/57ad7180-c5e7-49f5-b282-c6475cdb7ee7/TTTGallery/OldMachinist/_thumbs/bushinginstalled.jpg[/IMG][/URL] [FONT=Times New Roman]I also reamed out the welded in tilt cylinder bushings on the Bobtach and both ends on the tilt cylinder while I was at it. Now all they all have replaceable bushings [URL='https://www.skidsteerforum.com/DesktopDefault.aspx?tabid=52&gallerypage=1¤titem=8&path=OldMachinist'][IMG]https://www.skidsteerforum.com/Portals/57ad7180-c5e7-49f5-b282-c6475cdb7ee7/TTTGallery/OldMachinist/_thumbs/tiltbushings.jpg[/IMG][/URL] I ran a small brake cylinder hone in the tapered pinholes on the lift arms to make sure the pins would seat proper. These holes had no wear just a little rust but on any tapered mount hole must be clean for it not to start working around and get loose. I used delrin washers I also bought from McMaster Carr to take out some of the side play of the Bobtach. When I reassembled it every lined up perfectly. All together I spent about $250 and it took 6 hrs. which included making the bushings. In the future I figure it will take me no more than 1 hour to replace the bushings.[/FONT] [/FONT] [/QUOTE]
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