MY CORLISS

ENGINE BUILD

Part nine by Vince Cutajar

For some reason I did not fancy using the vice so I clamped the cylinder to the mill table. Used a new 5mm and 5.5mm drill and drilled and reamed 6mm the first valve hole.

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I then drilled 1.6mm the bolt holes and tapped it with the first and second 2mm tap.  I made sure I did not bottom out and continued tapping it with the last tap.

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Did the adjacent side similarly and then took it off the mill table and finished (very slowly) tapping the holes.


All the thirty-two 2mm holes were successfully tapped without any breakages.  Yes, I took my sweet time to do them, but as we say at work, better safe than sorry.  After a while, tapping 2mm does not seem so small.

More holes needed to be drilled and tapped in the cylinder, but I needed a break from tapping. So I started work on milling the steam chest pockets.  Marked it and then using the DRO roughed it out with a 6mm slot drill.

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I then used a 6mm end mill to finish it out to size.

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I found an off-cut from the eccentric which lended itself perfectly for the valve disk hub. So I started machining the hub.

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Flipped it over and faced off the back to size.

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Drilled and reamed a 5mm through hole and then a 6.5mm hole. Using a 7mm slot drill (I don't have small boring bars) I opened it up to the required depth.  And for the final diameter I stepped milled in 0.5mm increments the final 10 mm diameter.

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Lightly deburred the steps with a countersink tool.

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Now to drill the four mounting holes.  I used the 4-jaw chuck clamped to the mill table.  It worked a treat and I drilled the four 3mm clearance holes.

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I tried a 3mm bolt and it was a tight fit.




DRAWINGS HERE

PART EIGHT HERE  PART TEN HERE

 
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