Jefferson,

Ahhh ... I just noticed that your site included ship-building activity 
... another alternative is that your artifact MAY also comprise a 
babbitt-bearing and form part of a shaft-seal for a propeller-shaft on a 
big boat ... or as a part of the packing for the shaft-seal (cast, or 
occasionally driven into position around the shaft to provide a babbitt 
or "slipping" surface to support the "rod" or shaft, and help keep the 
wobble of the shaft from quickly wearing-out the compressible packing 
material [like, for example, oakum], with which the "stuffing-box" was 
mainly filled ... and allowing steam to escape around the shaft at the 
end of the steam-cylinder of a steam-engine ... of the type commonly 
used with steam-boats) ... both applications similar to the 
"babbitt-sleeve" already described.


    Traditional Babbitt bearings:

In the traditional style of a babbitt metal bearing, a cast iron 
<https://en.wikipedia.org/wiki/Cast_iron> pillow block 
<https://en.wikipedia.org/wiki/Pillow_block_bearing> is assembled as a 
loose fit around the shaft, with the shaft in approximately its final 
position. The inner face of the cast iron pillow block is often drilled 
to form a key <https://en.wikipedia.org/wiki/Key_%28engineering%29> to 
locate the bearing metal as it is cast into place. The shaft is coated 
with soot <https://en.wikipedia.org/wiki/Soot> as a release agent 
<https://en.wikipedia.org/wiki/Release_agent>, the ends of the bearing 
are packed with clay <https://en.wikipedia.org/wiki/Clay>, and molten 
metal poured into the cavity around the shaft, initially half filling 
the pillow block. The bearing is stripped, and the metal trimmed back to 
the top surface of the pillow block. Hardened babbitt metal is soft 
<https://en.wikipedia.org/wiki/Hardness> enough to be cut with a knife 
<https://en.wikipedia.org/wiki/Knife> or sharp chisel 
<https://en.wikipedia.org/wiki/Chisel>.

A steel <https://en.wikipedia.org/wiki/Steel> shim 
<https://en.wikipedia.org/wiki/Shim_%28engineering%29> is inserted to 
protect the face of the lower bearing and to space the cap of the pillow 
block away from the shaft. After resealing the ends with clay, more 
metal is then poured to fill the cap of the pillow block through the 
hole in the top of the pillow block cap that will eventually be a 
lubrication hole.

The two halves of the bearing are then split at the shim, the oil 
<https://en.wikipedia.org/wiki/Lubricant> holes cleared of metal and oil 
ways are cut into the surface of the new bearing. The shaft is smeared 
with engineer's blue <https://en.wikipedia.org/wiki/Engineer%27s_blue> 
and rotated in the bearing. When the bearing is disassembled the blue 
fills the hollows and is rubbed off the high spots. The high spots are 
scraped down, and the process repeated, until a uniform and evenly 
distributed pattern of blue shows when the shaft is removed. The bearing 
is then cleaned and lubricated, and shimmed up such that the shaft is 
held firmly but not binding in the bearing. The bearing is then "run in" 
by being run heavily lubricated at low load and revolution, completing 
the process of exposing the hard bearing surface. After final adjustment 
of the shimming, a very reliable and high load 
<https://en.wikipedia.org/wiki/Force> capability bearing results.

Before the advent of low cost electric motors 
<https://en.wikipedia.org/wiki/Electric_motor>, power was distributed 
through factories from a central engine via overhead shafts 
<https://en.wikipedia.org/wiki/Line_shaft> running in hundreds of 
Babbitt bearings.

The expression a "run bearing" also derives from this style of bearing, 
since failure of lubrication will lead to heat 
<https://en.wikipedia.org/wiki/Heat> build up due to friction 
<https://en.wikipedia.org/wiki/Friction> in the bearing, eventually 
leading to the bearing metal liquefying and running out of the pillow block.

~~~

You ought to test the metal on the inner (concave) side to see if it is 
composed of (or has a residual) babbitt-metal (babbitt would be very 
high in tin content) rather than solely or predominantly lead, see:

https://en.wikipedia.org/wiki/Babbitt_(alloy)

Regards,

Bob



On 7/20/2016 4:38 PM, Bob Skiles wrote:
> Jefferson,
>
> Looks like (one-half of a) a "babbitt sleeve" for centering a large 
> main shaft (like one which may be found in any system for distributing 
> power from an engine to other machines ... like connecting a 
> steam-engine to a sawmill, for example).
>
> The functioning of babbitt sleeves is explained in one example (ca 
> 1900), here:
>
> https://books.google.com/books?id=iqAiAQAAMAAJ&pg=PA93&dq=%22stuffing+box%22+babbitt&hl=en&sa=X&ved=0ahUKEwis7qin_oLOAhXG34MKHaBPC_s4ChDoAQgyMAI#v=onepage&q=%22stuffing%20box%22%20babbitt&f=false 
>
>
> Regards,
>
> Bob
>
>
> On 7/20/2016 3:02 PM, Jefferson Seaver wrote:
>> I’m hoping for help identifying the artifact pictured at 
>> http://imgur.com/gallery/4qjHX <http://imgur.com/gallery/4qjHX>
>> Material: lead
>> Probably dates 1850-1900
>> Associated with a site in Michigan that included a sawmill, 
>> shipbuilding, and brick making activity
>> Thanks for your help.
>>
>> —
>> Jefferson Seaver  |  616-262-0345
>>
>