[SEL] Babbitt Lapping Compound

[Judge Tommy Turner]

Curt,
    I'm curious how many folks have used the method that I have for 
crank bearings.  I have made bronze bushings and then seat them with 
babbit into the journal.  It makes a nice bearing surface and there is 
no scraping or lapping needed.  It takes time to do it and probably is 
not any less time consuming than the old fashioned way but I've never 
trusted my scraping ability as much as I'd like.  I'm like you, it looks 
like having the remnants of the compound potentially embedded in the 
babbitt could cause some big issues down the line.  The only way I see 
that it wouldn't would be if its somehow degradable but I don't see how 
it would be a very effective lapping compound if it was.

Tommy Turner
Magnolia, KY


>Rick,
>When I use lapping compound on bushings for our forging machines here at 
>work, I remove the cap and place a small amount of the compound at the 
>point along the bushing & shaft where the bearing is tight. I place it 
>at the junction between the shaft and edge of the bearing, where the 
>shaft rotation will sweep the compound into the bearing. I then put the 
>cap back on loose and fit a large funnel to the oil inlet. Then run the 
>machine and slowly pour about a quart of oil (320 vis) thru the funnel, 
>literally attempting to wash the compound, and the wearing away bearing 
>material out of the bearing. I use diamond lapping compound (5 micron) 
>and it works in seconds, so getting it back out of the bearing is of 
>paramount importance, otherwise a low bearing results.
>This process is on 660 brass bushings. I have never tried on babbitt 
>bearings. They claim it does not imbed in the babbitt, but that would 
>sure be my concern. I lean very strongly to "scraping" the high spots 
>away on babbitt. Babbitt is SO easy to work with, one could almost get 
>the "lazy" title associated to their name if they aren't will to invest 
>a minimal bit of time scraping in soft babbitt bearings. I don't even 
>use official scrapers on babbitt, just hit the high spots with a very 
>course rat tail file. This works great and is fast.
>Curt
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