The frame is made from a thick piece of Brass bar. The plans call for something about 9mm thick and 20mm wide and 90mm tall.
The thickness can be a few millimetres either way, as long as the bearing shoulder length is adjusted to suit.
To start, a piece of brass can be cut to length.
The ends finished square using a file with regular checking against a right angle. It can, of course, be machined on a mill if one is available.
Some layout ink helps to mark a centre line and the locations for the bearing hole and cylinder pivot.
Make sure the pillar drill is set up nice and square by placing piece of straight steel in the chuck and checking it with a right angle against the table.
Both holes can be drilled starting with a small drill to catch on the centre punch marks. Then increasingly larger drills can be used the hole is the correct size. For the bearing hole, a step drill can be used to get to the final 10mm diameter more quickly. With the step drill the work should be clamped to the table to prevent it moving.
The port holes just use a 2mm drill. Note that one hole as drilled right through but the second one only goes about half way.
The drill depth stop can be used to ensure the drill doesn't break through. To set the depth stop, lower the drill next to the work until it reaches the desired depth. Then tighten the nut and lock-nut, to mark this position.
The steam inlet port needs to be in line with the blind hole.
The location can be marked by extending the port hole placement up the front face and across the top of the frame.
Drilling should be done with the frame set vertical in a vice using a small square. After drilling down to meet the port hole, the top part of the hole can be opened out and tapped to accept the inlet pipe. The tapping should also be done by hand in the pillar drill to ensure it is square.
Once the bearing has been made it can be used as a guide to drill the mounting holes in the frame, a process called transfer drilling.
With the bearing clamped or held in place, a drill the same size as the holes in the bearing is used to mark one of the hole locations.
Then, the tapping drill used to drill this hole to depth and a tap used in the pillar drill to thread the hole.
After completion of this first hole, the bearing can be held by a bolt and the other 2 holes machined in the same way.
The port drillings in the top of the frame are shown above.
The two mounting holes in the bottom of the frame can be marked, but only one should be drilled and threaded at this stage.
Then the frame can be screwed to the base with this hole and the second mounting hole drilled via the base plate to ensure a perfect fit. Another example of transfer drilling.
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