Lower Cylinder end Cover
This cylinder end cover is more critical than the top cover. If you haven't made the top cover yet, then why not
make that first - just for the practice.The lower cylinder cover has to be perpendicular to the bore of the cylinder and the hole in the middle, for the piston rod, has to be concentric with the bore and parallel with the bore. The first criteria should already be satisfied by the machining of the cylinder casting.
Checking my particular casting proved it to be very accurate and so I was able to use the 3 Jaw chuck throughout. If your casting is more awkward then it may be necessary to use the 4 jaw to centre things up.
I mounted the casting in the 3 jaw chuck with he spigot facing outwards. I machined the spigot to make it central with reference to the outside of the casting. Also in this setting I machined the standard mounting point. I had to do this by hand as a full revolution of the lathe was not possible. Because this was a lengthy task I finished my mounting point 1mm over size. (This will need to be remembered when I machine the standard, so I can make compensations).
Machining the spigot and standard mount.
Next I reversed the casting in the chuck, griped by the spigot. In this setting I machined the back of the column mounting, the diameter of the rim and a locating ridge in the centre. Take care with the back of the column mounting, it is an intermittent cut and there's a lot of metal to remove. Use the tailstock for extra support if you need it.
Machining the bottom cover detail.
As before I made the rim 1mm oversize so the cylinder lagging would be a flush fit. Use the cylinder casting to check the size of the locating rim, this needs to be the best possible fit. I also found I had to cut into the cover face slighty at the bottom of the rim, to remove any radius left by the tool.
Important :
Without taking the casting out, now centre drill, drill and ream the hole in the centre. By doing this now you ensure that the hole in concentric with the bore.The remaining operations are to drill the 6 bolt holes around the edge. I marked these out again using the spirit level technique (
see top cover) but of course ensuring that the first hole was in the centre of the column mount. Whilst in the chuck I now machined away the spigot.
Machining away the spigot and marking the 6 holes.
To drill the 8 degree hole for the column mount I rotated my drill press table by 8 degrees and checked this angle using a spirit level of the column mount face. Then I centre drilled and drilled to size.
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Drilling the column mount with table at 8 degrees. |
The drilled lower cylinder cover. |
