Reed Electric

Metallizing Miracle: Saving Your Shaft

When electric motors come in for repair the bearing fits on the shaft are often worn too small to hold a bearing any more. This wear can be the result of:

    pulling the bearing off too many times for bearing changes
    the extreme pressure of carrying the load on the shaft
    from bearing failure

When a bearing fails it can create a significant amount of heat; enough heat to cause the inner race of the bearing to 'grow' too large for the shaft due to thermal expansion. The inner race then begins to spin on the shaft. The result can be a shaft many thousandths of an inch too small to hold a new bearing. In some cases the inner race will actually weld to the shaft and create straight 'threads' locking the inner race onto the shaft.The inner race must then be cut off of the shaft with a cutting torch using a scarfing technique.

Fortunately, most of the time a new shaft is not necessary because of a technique known as metallizing. The metalspray or flamespray process utilizes an oxy-acetylene gun which shoots molten metal onto the damaged area of the shaft where it builds up and replaces the existing metal of the bearing fit. The machinist applies enough metal so that the area of the bearing fit is .100" larger than the actual finished bearing fit size. He machines the fit on the shaft to size.

The following is a description of the process in detail (Click on Photos below to enlarge):

  1. The bearing fit before repair (photo 1)
  2. The shaft is placed in a lathe and indicated to within .0005" (photo 2)
  3. A carbon based masking release agent is applied to the shaft to prevent the metalspray from sticking where it is not needed (photo 3)
  4. The shaft is undercut and roughed up to allow for the metal buildup (photo 4)
  5. Bond coat is first applied so the metalspray will fuse to the shaft base metal (photo 5)
  6. A 2nd layer metalspray is applied to the shaft until the bearing fit is built up .100" oversized (photo 6)
  7. The shaft is cooled to room temperature allowing accurate measurements during the machining process (photo 7)
  8. The metalspray is machined down until it is .0005" over the actual bearing fit size
  9. Bearing fit is final polished down to it's final bearing fit dimension (photo 9)
  10. The finished product (photo 10)

electric motor bearing repair

electric motor shaft repair

electric motor carbon based masking

electric motor metal build up

electric motor shaft

electric motor metalspray

electric motor shaft measurements

electric motor bearing fit

Sorry image #8 is missing...

electric motor finishing

 

The metallizing process can also be used for motor housing bearing fits, shaft seal fits that have rubbed due to bearing failure, shaft extensions, and other applications where the existing metal of the motor or pump have been worn away. Metallized fits are just as durable as the original fits, and allow the repair of expensive motor parts at a very affordable cost. In sleeve bearing applications, the metallized finish is actually better than original as surface finish holds the oil film better. Fits can be resprayed many times if necessary over the equipment life, allowing multible rebuilds of motors and pumps with no loss in durability or performance. Metallizing has been in use for decades, and should be considered a viable option to bring the miracle of life back to your equipment at a small fraction of replacement cost.

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Reed Electric - LA
5503 S. Boyle Avenue, Los Angeles, CA 90058
Ph: 323-587-2284 / Fax: 323-587-2142

Reed Electric - Reno
5375 Louie Lane, Reno, NV 89511
Phone: 775-824-7333 / Fax: 775-824-7344