repairing bearing race mating surface on shafts and in bores

[JOSHUAZ2]

This may be common knowledge to some but was informative to me and confirmed past experience. Here is the story.

A friend who ownes a quality assurance lab was asked by a large manufacturer he tests for what was the best method of repairing shaft and bores to tighten bearing race fit without major machining. They tested bearing retainer, prick punching and prick punching with retainer (I had never thought of that). In 10 tests of each method 5 testing inner races and 5 testing outer races the results were.

punching only. at 30-40% of max load bearing fit became loose and back to close to what was started.


retainer fluid. 2 inner races and 4 outer races survived 100% others became enlarged to varying degrees.


punching and retainer compound. all survived 100% load for 50 hrs.


This was a very small scale test and was of limmited focus but the trends should scale. I can't provide specific data because I wasn't the one the test was done for and don't have access to it.

Hopefully this helps someone. I know how I will performe guicky fit repairs in the future.

Roy

 

[Daver]

Ok, newbie here... Can you elaborate on retaining fluid? Are you talking about something like epoxy?

 

[Rbeckett]

More likely Loctite bearing set. It works in the absence of air and when properly cured it will lock a bearing into a cavity very nicely. If using the punch prick method I tend to use a slightly dulled pin punch to vreate a more rounded dimple with a good uniform raised edge around the center. Combining the two had saved a number of commercial mower shaft housings we used to rebuild from having to get metal sparayed ammd rebored. Metal sprawing and reborung is time consuming and expensive and best used on a shaft as opposed to a recess. Done em both waysm but the shafts seem to hold up better for longer before being repaired again. Hope thhis helps
Bob

 

[Richard King]

Good topic Roy

Over the years I have knurled the area and turned it down so the shaft is true. Im not a big fan of center punching but use itonly in an emergency situation. I just had a quill chrome plated because it was loose. That is probably the best method but also the most expensive. You have to grind down the shaft have it plated and reground to the original size. I also use Loc-Tite but be careful not to get it into the bearing. I would go to MSC and look for the one that fits your needs. I also love to use the Loc-Tite on bolts and bearing retainer nuts as I am sure they won't break loose. I prefer the Blue so it can be removed with out heat as the Green requires.

 

[Kent]

Repairing fits on industrial equipment is part of our business. Flame spray is sometimes the only option, but remember a sprayed shaft or housing is filled with particles - which will compress under load. Punching and retaining compound could do in a pinch but I wouldn't count on them. (It's nothing you could ever charge anyone for doing.)

The best solution for housings is to over bore them and use a product called an EZ sleeve - they are relatively inexpensive high grade cast iron sleeves made for the purpose. Overbore the housing, press (or shrink with CO2) the sleeve into the housing, and then finish bore the sleeve to the proper size. The best shaft repair is to weld it and then remachine to the proper size.

 

[Cheeseking]

A co I worked for many moons ago did on-site field machining in power plants, steel mills. In addition to weld build up method, I repaired many "oopses" or worn journal sections on large shafts etc using a brush plating technique. (Electrochemical metalizing is the term I believe) We could apply various alloys to substantial thickness as in .1 or more with high speed nickel. the resulting repair is covalent bond to parent material unlike flame spray which is mechanical. Like any process, brush plating has limitations as well as advantages but anyone in the business of repairing shafts journals etc should be aware of it.
http://o-e-m.net/process.htm