Simple Oscillating Steam Engine - Main Bearing

The Bearing provided a running surface for the main axle and was also designed to give clearance between the crank and the frame.

Click for larger drawing









First a chunk of bronze slightly longer than the bearing was placed in the chuck with enough material sticking out to allow the machining of the 'through frame' part of the bearing.

The diameter of the protruding section was turned first. This was turned to be a close fit in the hole in the frame.









Next the bearing was centre-drilled and drilled just under final size by 0.1mm. Then a reamer was used to finish the hole.

Centre drilling



The drilling was done the lathe running at a fast spindle speed (700rpm), however the reamer was used with the lathe running about 100rpm. All holes were drilled right through.









The diameter of the outer shoulder was also turned in this setting.

A sharp pointed tool was used to ensure that there was no radius where shown. The length of the protruding part was slightly longer than the width of the frame to ensure the crank would not rub against the frame.









The part was reversed in the chuck and the protrusion on the other side was machined. The length of this protrusion was arbitrary as it would only set the distance between the flywheel and the frame. It could also be left with a radius at the root.

The square shoulder previously cut enabled the part to sit back against the chuck jaws helping everything stay square.









Whilst in this setting the 3 mounting holes were marked out. This was done by placing a centre punch in the tool post and a spirit level was used on the chuck jaws to create 3 evenly spaced holes. Hole positions using this method were not perfect, but visually acceptable.

Marking the mounting holes









Once marked out the bearing was removed from the chuck and drilled on the pillar drill. The top of the vice jaws were used to support the work.

1.8mm clearance holes were drilled to accept the 10BA screws.











The finished bearing