[SEL] Babbitt lapping compound

Elden DuRand edurand at mchsi.com
Thu Apr 3 13:44:27 PDT 2008


Jim:

The instructions say that the lapping material (comes dry and you mix it to a paste in oil) does not imbed in either metal.  

I found when lapping bearings in a F-M 1-1/2hp Z the crankpin diameters did not decrease by any measureable amount.  Sure, the shaft and bearings weren't shiny when I finished.   Before running it, I had the bearings set-up for a moderate drag which lessened quite a bit after the first run.  If I were really curious, I'd pull a bearing cap after about the three hours running the engine's got on it and have a look.  If the manufacturer of the compound is right, the finish should be shiny on the crankpins and nearly so on the bearings.

But I'm retired and lazy!   :-)

BTW, after the first short run, when I turned the grease cups, the grease came out of the journals black so I turned 'til it was clean, wiped up the mess and now, after the rest of the running, the grease is almost completely clean coming out, so I'd guess that no more lapping is occuring.

Take care - Elden 

> -----Original Message-----
> From: sel-bounces at lists.stationary-engine.com
> [mailto:sel-bounces at lists.stationary-engine.com]On
>  Behalf Of JIM KIRKES
> Sent: Thursday, April 03, 2008 01:26 PM
> To: The SEL email discussion list
> Subject: Re: [SEL] Babbitt lapping compound
> 
> 
> I find it very difficult to believe that there is an 
> abrasive that "morphs from abrasive to lubracative."  How 
> about some more details.  One other question 
> about bearing 
> lapping, how do you get the abrasive that is 
> imbedded into 
> the babbitt out?  The lapping process depends on 
> the softer 
> material becoming charged with the abrasive and 
> cutting the 
> harder material not the other way around as has 
> been stated. 
> I would not touch babbitt  lapping with a ten foot pole.
> 
> Jim
> 
> Jim and Diane Kirkes





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