Simple Oscillating Steam Engine - Frame

The frame was made from a thick piece of Brass bar. The plans call for something about 10mm thick and 20mm wide.


Click for larger drawing









First a piece a brass was cut slightly over long from a piece of brass bar.

The ends can be finished square using a file with regular checking against a square, or can be machined on a mill if one is available.









Next the bar was painted with 'marking out blue'. A centre line and lines for the bearing hole and cylinder pivot were marked out using the callipers set to the correct distance.



The pillar drill was checked for squareness by placing a piece of straight steel in the chuck and checking it with a square against the table.

Then both holes were drilled starting with a 2.5mm drill which would 'pick up' on the centre punch marks.

Increasingly larger drills were used in steps of 0.2mm until the hole was the correct size. For the bearing hole a step drill was actually used to get to the final 10mm diameter more quickly. With the step drill the work had to be clamped to the table to prevent it moving.










The port holes were drilled with a 1.6mm drill to pick up the centre punched marks.

One hole was drilled right though but the second one was only drilled just over half way through.

To ensure that when drilling this 'blind hole' the drill didn't break through by accident the depth stop on the pillar drill was used. To set the depth the drill was placed next to the work and lowered until it reached the desired depth. Then the nut and lock-nut were moved down on the drill stop, to mark this desired depth.

This photo shows the depth stop on a typical pillar drill.









Finally the inlet port was drilled to meet the blind hole.

First the hole was marked by extending the hole location up the front face and across the top. The centre of the frame width was also marked along the top before centre punching the location.

Drilling was done with the frame set vertical in a vice using a small square. After drilling down to meet the port hole, the hole was widened over part of the depth and the tapped to accept the inlet pipe. The tapping was also done by hand in the pillar drill to ensure it was square.











Port drillings complete











Once the bearing had been made it was used as a guide to drill the mounting holes in the frame. The process used was called transfer drilling

With the bearing clamped or held in place, a drill the same size as the holes in the bearing was used to mark one of the hole locations.

Next the tapping drill was use to drill this hole to depth and a tap was used in the pillar drill to thread the hole.

Once this hole was complete it was used to secure the 2 parts together so the other 2 holes could be formed with the same method.