Stuart No 1 - Bottom Cylinder Cover

The bottom cylinder end cover was more critical than the top cover. It had to be perpendicular to the bore of the cylinder and the hole in the middle needed to be concentric with the bore and parallel with the bore.

Checking this particular casting showed it to be very accurate and so it was possible to use the 3 Jaw chuck throughout.


The casting was placed in the 3-jaw chuck with the spigot facing outwards. The spigot was machined to make it concentric the outside of the casting. Also in this setting the standard mounting surface was machined. This was done by rotating the chuck by hand, because a full revolution of the chuck was not possible.









Next the casting was remounted in the 3-jaw chuck and held by the spigot.

In this setting the back of the column mounting was machined (note the back of the column mounting is an intermittent cut and there's a lot of metal to remove. Use the tailstock for extra support if needed).

The final diameter of the rim and the locating ridge for cylinder were also formed in this setting. As with the top cover, the rim was made 1 mm oversize, so the cylinder lagging would be a flush fit. The finished cylinder casting was used to check the size of the locating rim. This had to be the best possible fit.









Without removing the casting, the piston rod hole was centre drilled, drilled and reamed to final size. This ensured that the hole was concentric to the locating ridge and therefore concentric to the cylinder bore.









The remaining operations were to drill the 6 bolt holes around the edge. These were marked these out using the spirit level technique (see top cover) but ensuring that the first hole was in the centre of the column mount.

Whilst in the chuck marking the holes, the spigot machined away.









The 8 degree hole for the column mount was drilled by tilting the drill press table.

Then the hole was centre drilled and drilled to size.





Stuart 1 Index