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The piston was made from brass and included the connecting rod and bearing assembly.
Click for larger drawing |
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A piece of bar slightly larger than the required piston diameter was placed in the chuck. It was left sticking out the equivalent of the cylinder length. |
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The parting off tool was used to reduce a section of the bar below the piston. |
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The piston was then turned slightly oversized or until it was a very tight fit in the bore. Ideally a piston hone should then be used to smooth out the machining marks on the piston. A cheap substitute is some very fine (2500 grit) paper supported on a flat edge such as a file. Care was taken to ensure that the piston remained parallel. Fine sanding strokes were used until the piston was a snug fit in the cylinder. Then it was deburred gently to finish. |
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After the piston was finished the rod was pulled forward in the chuck to allow the piston rod and 'big-end' bearing to be tuned. The material below the piston was removed to a diameter of 8mm. |
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Next the connecting rod was turned to a diameter of 5mm. |
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Before the finished part was parted from the bar it was removed from the chuck and marked out for the crank pin hole. |
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The additional length of bar enabled the piston assembly to be clamped in the Vee block and drilled in the pillar drill as shown. |
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Finally the work was replaced in the chuck and parted from the bar. As usual the tool was retracted part way through so that a file could be use to chamfer the bottom edge. |
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The finished piston assembly |
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