Top Cylinder End Cover

I consider this component to have no critical dimensions. To look right of course it needs to be made as accurately as possible but the only thing the top cylinder cover has to do is seal against one end of the cylinder casting - easy !

First I chucked the end cover in the 3 jaw chuck, with the spigot facing outwards. Then I skimmed the spigot until is was central. This was done to ensure that the spigot was central referenced from the outside edge of the casting (the golden rule).

Centring the spigot

Then I reversed the cover in the chuck and used boring and turning tools to get the profile given by the drawing. I decided to make the diameter of my end covers 1mm oversize so that they would fit flush with the cylinder lagging.

Turning the underside of the top cylinder cover

The detail on the underside of the cover was turned using a boring tool and a turning tool. I also used a drill to help form the indent in the middle. Once the cylinder was a close fit on to the turned locating rim, the machining was finished. If you want to scribe a circle for the PCD of the screws then this is the time to do it. I chose to mark the other side of the casting instead so that I would have the flat side to drill against.

I removed the casting from the chuck, sawed off the spigot and put it back in the chuck to machine the top surface. I used some paper in each of the jaws to avoid marking the edge of the cover.

Turning the top of the cover.

The dome was formed using a turning tool, file and emery cloth. I marked the screw locations on this side. I didn't scribe a full circle as this would show on the final part instead I just made a dent with the lathe tool in the correct place which was then marked more heavily with a centre punch and then centre drilled, and then drilled to size.

If you're wondering how I divided the circle into 6, here is how I did it. I have a small spirit level which I cut from an old wood working tool. I use this on each of the jaws (at the back and the front) to give me 6 equally spaced marks.

The sprit level on one of the jaws

This is not 100% accurate but I think it is accurate enough to make the component look right and any slight deviations will not matted if you are drilling the other holes to suit.

The finished top cover