*
The silvery finished, furniture top, cap, ferrule, sleeve, flange, connector nuts arrived. As did the five x 5kg weight disks finished in grey Hammerite. The nuts were fine and arguably rather better than the brassy ones I had been using so far. All a matter of taste though.
The weight disks were very rough on the outside edges where the minimum of fettling had occurred after casting. I saw no reason not to turn the rims to remove the roughness and sharp edges if only they would fit on my lathe. By using an inverted boring bar and expanding the 3 jaw chuck into the ~51mm bore I was able to take cuts on the outside surface of the 230mm [9"] diameter x 25mm thick disks. I am usually limited to a maximum of 180mm [7"] in the 4-jaw chuck. A steel disk, with soft packing, backed up by a live center ensured the disks did not escape from the chuck jaws. [see image above]
I ran the lathe at 45rpm, in slowest back gear, to remove the worst of the casting roughness. Then increased to 60rpm to smooth things off once there were no more shock loads. It was taking about half an hour per disk using the lathe apron's slowest feed but I still felt it worthwhile. I would never be happy seeing the heavily tapered and very rough circumferences stacked together all higgeldy-piggeldy on the declination shaft. A rub with a coarse file rounded off the previously sharp and ragged rear edges to make them look much smarter and much safer to handle.I think you will agree that the final result was worth the extra time and effort. I have done four but will leave the last in case I don't need it to balance the 7" refractor OTA. Not bad for about 100DKK, £10, $13 each plus P&P. They will look far more uniform with a decent coat of paint.
Click on any image for an enlargement.
*
No comments:
Post a Comment