Repairs to electric motor shaft journals 1

[GusD]

We have always used hard-chrome to repair bearing journals on our electric motor shafts.Fifteen or twenty years ago we did experiment with spray welding, but the results were
disastrous in some cases,reason why we stayed with chrome of motor shafts,unless the damage was greater han .020" in which case we fabricated a new shaft.
From time to time, the question arises why don't we use
sub-merge arc welding or some other form of repair?
The reason we stayed with the chrome process was easy to explain.It was cost competitive and most important very reliable.I would appreciate any information in this matter

Thanbks a lot
GusD
obvious.when damage was limited to Our shafts are mostly 4140 or 1045
materials,speeds up to 3600 rpm

 

[evelrod]

Gus, I think you got it right the first time. Hard chroming is still the best in my book. We use it to repair seemingly irreplaceble crankshafts in air compressors and I use it on one occasion to repair a scorred crank journal on one of my race engines.

Rod

 

[Vague]

Hi Gus!

I've work in a machine shop who specialize in electrical motor repair and i'd say that 90% of all shaft restoration we're made by welding, either by SMAW or FCAW process. The remaining 10% was divided equaly between chrome plating repair and manufacture of a new shaft.

Despite those figures the chrome plating solution is the best one when you don't have severe damage. It's not too costly and you don't induce thermal stress nor deformation.

The manufacture of a new shaft was limited because it imply depressing the shaft from the laminations wich often lead the latter to be damaged in the process. The other reason is because the welding method is not expensive.

Two procedures can be use when restoring a motor shaft by welding, rebuilding or do a ''stub shaft''. Careful if you rebuild; you can't weld the bearing seat alone! You have to start welding at shaft hole location and go down to shaft end. The stubbed shaft procedure could be resume by the following: 1- Cut the shaft at shaft hole location
2-Machine the remaining end with a preparation angle and a small hole for positionning.
3-Cut a new shaft (4140 is often used) and machine an angle with a pin to match the hole and assure concentricity.
4-Weld the two parts together (limit heat input and allow slow cooling).
5-Machine the shaft.

We have stubbed up to 10 inch diameter shaft succesfuly in the past. In 15 years less then 5 shafts were found defective.

If you need more info's feel free to ask.

PS: Excuse my english...

Vague

 

[automatic2]

Chroming has limited ability in regards to adherence, often resulting in galling. A tighter bearing fit will increase the durability but inversely decrease bearing life. Grinding the shaft then using a metal sleeve supplied by many bearing manufacturers proves good service.

 

[olympic]

If I interpreted this correct, you are grinding and re-chroming worn bearing surfaces. Does the chrome plating ever come back with damage form flaking. I know that this is a reason why some high performance engine techs stay away from chrome. Also, in other applications similiar to yours, which requires machining for a stub shaft, I used chrome plate induction hardened shaft, which was machined out as to produce a very hard 0.060-0.100" tubing which could then be heated and shrunk onto the damaged shaft. THis provided a very durable bearing surface with a Rc hardness of at least 60 below the chrome.