Bobcat 763 Worn bobtach cylinder pin fix

[mini]

Here is my fix for a worn out hole, I did not want to use the weld-on replacement bushings, and my milling machine was too small to fit the bobtach on it, so I came up with this crazy idea to ream the holes by hand, it required my lathe to make the bushings, so it's not a fix for everyone, but it sure worked for me, anyone interested please see the pdf file I made of the process. http://www.rockcliffmachine.com/bp.pdf just a little something to give back, I have taken so much from this forum, a huge thanks to all who have posted to help me, Newbee worn out 763 bobcat owner Thanks Mini

 

[Fishfiles]

I have made bushings and pins for equipment before and have found that what you have when finished is not as good as what you can buy , first off the material you use , you can use good material if you have it , but the hardening process that is done to the pins and bushings after they are finished , accompanied with the cost of materials is something that you can't reproduce for a cost that is less than what they usually sell the parts for and then add in your time ---------it will get you out a bind on obsolete parts and working in the boonies --------------what do you think on the situation Olde' Machinist

 

[OldMachinist]

I have made bushings and pins for equipment before and have found that what you have when finished is not as good as what you can buy , first off the material you use , you can use good material if you have it , but the hardening process that is done to the pins and bushings after they are finished , accompanied with the cost of materials is something that you can't reproduce for a cost that is less than what they usually sell the parts for and then add in your time ---------it will get you out a bind on obsolete parts and working in the boonies --------------what do you think on the situation Olde' Machinist

I partly agree with that. Pins I think should be purchased OEM when possible, the material and heat treating have been engineered to be able handle the loads and stresses of the machine. Bushings whether weld on or pressed in aren't as critical as long as they're done correctly. Weld on bushings should only be replaced by a highly skilled welder. If a home made pressed in bushing fails the BobTach isn't going to fall off and kill someone but if a incorrectly heat treated pin fails it could be catastrophic.

 

[mini]

I partly agree with that. Pins I think should be purchased OEM when possible, the material and heat treating have been engineered to be able handle the loads and stresses of the machine. Bushings whether weld on or pressed in aren't as critical as long as they're done correctly. Weld on bushings should only be replaced by a highly skilled welder. If a home made pressed in bushing fails the BobTach isn't going to fall off and kill someone but if a incorrectly heat treated pin fails it could be catastrophic.

Hi guys Forgot to mention, I used a brand new OEM Bobcat pin, and OEM Bobcat Cylinder eye bushing, the 2 bushings that were press fit into the newly cut holes in the bobtach were purchased too, my tilt cylinder is perfect now, no play at all, and the only danger to others, is me behind the controls

 

[Rojas]

I used a right angle attachment on a Bridgeport and lined bored the egged shaped holes oversize. Used a piece of .875" drill rod to make a boring bar and ground a .375" HSS end mill to use as a cutter. I tack welded a couple of supports to the Bobtach and clamped a bushing to these to support the extended end of the boring bar. I think I bored the holes to 1.5". I made some interference fit bushings out of bar stock with a chamfer on one end. I ground a chamfer on the outside flanges on the bobtach. Heated the flanges and pressed the inserts in and welded flush all round on the chamfered sides. I probably spent the better part of 6 hours from start to finish on the boring operation. Now that everything is fabricated I could do the next one in a couple hours.

 

[mini]

I used a right angle attachment on a Bridgeport and lined bored the egged shaped holes oversize. Used a piece of .875" drill rod to make a boring bar and ground a .375" HSS end mill to use as a cutter. I tack welded a couple of supports to the Bobtach and clamped a bushing to these to support the extended end of the boring bar. I think I bored the holes to 1.5". I made some interference fit bushings out of bar stock with a chamfer on one end. I ground a chamfer on the outside flanges on the bobtach. Heated the flanges and pressed the inserts in and welded flush all round on the chamfered sides. I probably spent the better part of 6 hours from start to finish on the boring operation. Now that everything is fabricated I could do the next one in a couple hours.

Nice Rojas, very creative, right angle attachment, long boring bar, and tak welded support, " it's for sure a somewhat difficult spot to machine, "

 

[Rojas]

Nice Rojas, very creative, right angle attachment, long boring bar, and tak welded support, " it's for sure a somewhat difficult spot to machine, "

The creative work was already done by the guys who use and sell the line boring machines. I watched a few of the videos and put it together with the resources I had. I also welded up one side of the lower pivot bushings that was egged and bored that back to factory size. I had to swing the turret about 45 degrees give or take and extend it to keep from having a large overhung load on the bed. The bobtach overhangs the table by a few inches on each end if I recall correctly.

 

[Fishfiles]

The creative work was already done by the guys who use and sell the line boring machines. I watched a few of the videos and put it together with the resources I had. I also welded up one side of the lower pivot bushings that was egged and bored that back to factory size. I had to swing the turret about 45 degrees give or take and extend it to keep from having a large overhung load on the bed. The bobtach overhangs the table by a few inches on each end if I recall correctly.

When the weldment bushing holder of the bobtack pinswhen it is wollowed out , I buy the weldment from the dealer , it really isn't that bad like 70 $ US each plus bushings , an ach gauger works best , but a torch is sufficent and cut the weldment off flush with the gusit plates of the bobtach then cut round the edge of the weldment , about 1 hour of cutting both sides, tach weld the weldment into place while assembled to ensure alignment , disassemble and total weld , about 1.5 hours , reassemble about an hour , 4 hours labor to rebushing the bobtach -----------to rebuild the boom arms a-taper , I use the kits sold by Construction Tool Parts out of Portland , Oregan ( very nice people , who have lots of knowledge and products for Bobcat and other brands) tack weld a flat plate to the arm of the boom and use an magnetic drill press to drill the hole thru the boom , insert the bushing , assemble for alignment , weld in and your finished , Ctp also sells Bobtack pins , tilt pins , seal kit , hammer points and seal kit , and all kinds of other equipment parts , CPT = 1800 500 5221 , John or Jackie

 

[Tazza]

When the weldment bushing holder of the bobtack pinswhen it is wollowed out , I buy the weldment from the dealer , it really isn't that bad like 70 $ US each plus bushings , an ach gauger works best , but a torch is sufficent and cut the weldment off flush with the gusit plates of the bobtach then cut round the edge of the weldment , about 1 hour of cutting both sides, tach weld the weldment into place while assembled to ensure alignment , disassemble and total weld , about 1.5 hours , reassemble about an hour , 4 hours labor to rebushing the bobtach -----------to rebuild the boom arms a-taper , I use the kits sold by Construction Tool Parts out of Portland , Oregan ( very nice people , who have lots of knowledge and products for Bobcat and other brands) tack weld a flat plate to the arm of the boom and use an magnetic drill press to drill the hole thru the boom , insert the bushing , assemble for alignment , weld in and your finished , Ctp also sells Bobtack pins , tilt pins , seal kit , hammer points and seal kit , and all kinds of other equipment parts , CPT = 1800 500 5221 , John or Jackie

Nice job. I need to do the same, but my adjustable reamers i don't think will be too happy with me trying to cut very much per pass. I'm not sure how bad the wear is, but its more than i'd like.
I may need to weld some guides to the bobtach to hold a boring bar straight to clean it up and do as you did, machine some press fit sleeves.