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 | Ted Kennedy
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2001-03-09 25240
I recently repaired my Cub Cadet 407 backhoe by installing hardened steel bushings at all of the pivot points. The design of the unit had no-replaceable bushings and the dealer was clueless as how to go about installing new ones, he advised me to replace both the boom and the dipper along with all of the pins. In aerospace engineering we frequently purchase components and hardware from either McMaster-Carr and/or Carr Lane (www.mcmaster.com/ and www.carrlane.com/). I bought enough self-adjusting spring steel bushings from McMaster-Carr of the appropriate outside and inside diameter, a set of new pins from Cub, and rented a magnetic base drill press. I center indicated each bore, used the appropriate ream after positioning the magnetic base drill press, and opened the worn holes to size in one operation. Pressing in the bushings was easy, just drove them in using a wooden dowel and hammer. The hoe operates perfectly with no binding or slop and the next time I need to re-bush, all I have to do is drive out the worn ones and replace. The total cost including rental of the drill press, and all parts was $255.00, to buy a new boom and dipper stick, $2700.00. If anyone needs unusual parts, tools, jigs, storage items, etc., check these sources out.
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| JeffM
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2001-03-09 25254
Ted, thanks for the useful info and instructions! Your technique can be used in a variety of pivoting wear situations. Although I'm an EE/Computer Scientist by education, in a past stint with a mechanical design engineering team I too relied on McMaster-Carr, but had kind of forgotten the breadth of items I could source from them. Now I'll exhibit some of my broad ignorance: could you please describe a magnetic base drill press in more detail, specifically the capabilities and operation of the magnetic base? I've had relatively little exposure to machining operations and I'm a curious type. ....
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| Ted Kennedy
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2001-03-09 25264
Sure Jeff, the magnetic based drill press enables its user to make repairs that normally would require full disassembly, jigging on a table to make normal (right angle to surface) to the bore center line, and ream/bore using either a two axis machine or drill press. You know, machine shop stuff. In my case, I was able to remove the dipper stick and just place it on a couple of saw horses to ream out the points that attach to the boom. I applied the magnetic press to the dipper stick itself, centered it at each hole using plug gage/center, removed the center, turned on the magnet's current, then reamed. The drill press I used has enough axis adjustment to compensate for the slight angularities of the part being drilled. The magnet holds the press in exact position, exactly normal to the bore. I actually did the bucket end of the dipper while it was still assembled to the boom (suspended from the ceiling using a web fabric sling and hoist just long enough to make alignment and then turn on the magnet), and when my wife saw the drill press sticking sideways off of the dipper she couldn't believe her eyes until I let her in on the secret, "it's done with a magnet." (Note: parts that have a taper in two directions may prevent you from attaining normal to the bore C/L, and you won't be able to shim the magnet because it requires a fairly flat surface to hold) My wife asked me why I just didn't use a hand drill. The answer is that there is too much torque and pressure required for a hole this size, and no way to ensure normal, using a hand drill. I learned how to perform this operation from one of our tool makers: don't bring a big part to the machine shop, bring the machine shop to the big part! Cheers! ....
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| JeffM
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2001-03-09 25268
Thanks for the lucid explanation, Ted. I learned something here that I can see having some use for in the future. ....
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