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The Babbitted Bearings 2
Make a trough of the asbestos paper or thin sheet metal, support it in the branch opening of the wye so that the babbitt, when poured, will not land directly on the shafting (see Fig. 81). Quickly pour in the molten babbitt until the shafting is well
covered. When it has cooled, remove the centering and clamping screws and withdraw the shafting. A greater amount of expansion may have taken place in the casting than in the shafting and, upon cooling, the bearing may be extremely tight. If the shaft cannot be twisted free in the vise, hold a block of wood against its end
and drive it through with a hammer. If it is still tight after being cleaned out, smear a mixture of cutting oil and rotten stone in the bearing, then push the shafting back in and work it around. This operation is known as lapping, and if it is not overdone a perfectly smooth turning action will result.
Now make up the declination axis tight in the heavy flange K, and slip one collar over it, up against the flange. Smear shaft and collar with the lampblack and oil, then approximately center it in tee E, and fix the second collar in position against the tee face. Some means of adjusting the two axes perpendicular to each other
must now be found. The success of the final adjustments is dependent on the accuracy of this setting, so take plenty of time with it as it cannot be corrected after the babbitt has been poured, except by melting out the bearing.
In order to adjust correctly the position of the declination axis, the polar axis must be temporarily screwed into the branch of the tee E, and the shaft then inserted
in its bearing, already made. Rig up a makeshift pointer on the wye, contacting the declination axis at some point; then rotate the polar axis.through 180° and see if the pointer again contacts the declination axis. By repeated trials, and adjustment of the supporting screws in the tee, a very accurate setting can be arrived at.
Carefully, now, so as not to disturb the setting of the declination axis, unscrew the polar axis from the tee. Support the declination assembly as in Fig. 81, and babbitt. Be very careful in pouring not to bring the level of the molten metal up too high in
the branch opening, or it might not be possible to screw the polar axis all the way back in.
When cool, remove the shaft from the bearing, and use gasoline to flush out the lampblack, burned oil, and other foreign matter. If the bearing is tight, lap it in as already described. A bearing scraper is a useful tool for dressing up rough parts. Finally, cut two washers of leather or other friction material and insert them ahead of the clamping screws, to cushion the thrust of the latter against the shafting.
Screw the polar axis back into the tee, and pin it securely in its original position; then smear clean lubricating oil on both axes, return them into their bearings, and the assembly is completed.
Further suggestions and portable mountings
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