MY CORLISS
ENGINE BUILD
Part nine by Vince Cutajar
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.
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.
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.
I then used a 6mm end mill to finish it out to size.
I found an off-cut from the eccentric which lended itself perfectly for the valve disk hub. So I started machining the hub.
Flipped it over and faced off the back to size.
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.
Lightly deburred the steps with a countersink tool.
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.
I tried a 3mm bolt and it was a tight fit.
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