Metal spray: rebuilding worn bearing and seal surfaces

Metal spraying is one of our specialties, and it shows up inside many of our part repairs. The idea is simple: a worn shaft is a shaft that is too small. Spray it back to oversize, turn or grind it to the right diameter, and the bearing or seal fits as it did when new.

At a glance

• Rebuilds worn journals and seal areas
• Used on brake piston seal areas, trunnion diameters and yoke seal diameters
• Part is machined back to size after spraying
• A spray gun adds metal with far less heat than weld build-up

How the process goes

Spraying is a sequence, and the machining matters as much as the spray. The surface is cleaned and roughened so the sprayed metal grips it. Molten or semi-molten metal is then sprayed on in layers to a thickness over the finished size. The part goes back on the lathe, where the coating is turned to the original diameter.

1. Clean the part and cut the worn surface true.
2. Roughen the surface so the coating bonds.
3. Spray the metal on until the surface is over size.
4. Machine the coating back to the original diameter.

What it suits

Metal spray is a wear-surface repair. It is the right tool for bearing seats, seal diameters and journals, where the job is to put the right size back under a bearing or a seal. Parts that need strength across the joint itself are better served by weld or a sleeve, and the full comparison is in the guide on metal spray, sleeve or weld.

The question people ask most is covered on its own page: is metal spray as strong as new metal?

Why shops spray instead of weld

Spraying puts little heat into the part. A long, slender shaft or a thin-walled piston is less likely to distort than it would from weld build-up around the full circumference. That is the reason it suits pistons, seal diameters and long shafts, such as pump and turbine shafts and motor shafts.

What spray gives a rebuilt part

The finished result is a surface at the original diameter, smooth and round, that takes the original bearing or seal. Because the coating is machined after spraying, the size on the print is the size you get back. If you have a drawing, send it. If you only have the worn part and the mating bearing or seal, that is enough to work from.

What to send

Photos of the worn area, the part name, the machine it came from and the diameter you need back. The old bearing or seal helps too. Attach everything to the quote request or call (775) 359-5570.