Don't make this Mistake

Picture, for Question for June 2019

What is it?

METRIC MADNESS

Pat loved Jaguars. He had many of the factory special tools and was very adept with them. For that matter, Pat loved all British cars. Rebuilding a Jaguar engine was a pleasant thought and he was anxious to see the one he was presently working on run.



Because of distractions, Pat liked to build engines after hours _ when there weren't phone calls or customers showing up. The quiet evening hours were perfect for Jaguar engine building, and this evening was going to be the one for this straight-six XKE engine. He carefully washed the pistons, rings, crankshaft and bearing caps and laid them out for assembly.



One by one, he compressed the rings and slipped the pistons into their new bores. Every rod cap fit snugly in its place and Pat torqued the rod nuts in place. But then he remembered he didn't have cotter pins to lock the rod castillated nuts. In a moment of panic he rifled through the parts room bins looking for cotter pins. Good news! There was a full box of cotter pins.



Everything went without a hitch -- or so he thought. By the next evening, he had the engine running. It purred like a kitten _ a Jaguar kitten. Only this one was going to take a bite, a big bite, and when it did, it would cost him dearly.



Within a few days the car came back with no oil pressure and making horrible noises. Pat pulled the oil pan only to find it full of metal shavings. Brass, aluminum, iron and copper. The engine had totaled itself. Or in the vernacular, "Gone to lunch."



Broken hearted, he pulled it down to find out what went wrong. He thought, "Was the crankshaft bent? Did the customer shift to first gear while going 100? Was this sabotage? Who hates me? Why can't anything ever be easy? Will this cost my job?" He decided to face it the next day and went home early.



While he was gone, the shop foreman examined the metal shavings in the oil pan.



He had begun to think someone had sabotaged the job by pouring metal shavings in the engine. There was an overabundance of small pieces that looked like the tail ends of cotter pins. Upon closer examination, he realized they were the tail ends of cotter pins.



The cotter pins from almost every rod bearing nut were missing. Why? Because they were the wrong size _ too small. They vibrated up and down in their holes until they broke apart and dropped into the oil pan. Most pieces were too large to do any damage but some managed to get sucked into the pump, where they were ground into small shards, which circulated through the engine and ruined everything.



The oil pump was a scarred mess. Every crankshaft journal was destroyed. The cylinder walls were also badly scuffed from the metal in the oil. Only the overhead camshaft escaped destruction. This was not a case of sabotage, but rather a case of lack of attention to detail.



The foreman carefully combed Pat's work area for more clues, since he couldn't question Pat. In a box under the bench he found the original cotter pins. They were considerably bigger than the ones Pat had used. The difference in size was really quite obvious.



While he wondered why Pat had substituted smaller pins he checked the parts room for the right size. There were none. There were pins that were too big and pins that were too small. He carefully examined one of the old ones and noticed it had a red color. Metric! It was metric and the ones in the parts room were American size!



The next day the foreman didn't say anything to Pat about the job. He let him disassemble the engine without interruption. At lunch time, he called Pat into the office to discuss his findings. When asked what had failed, Pat lied and told him the crankshaft was machined wrong. The foreman pressed, "Are you sure?"



Pat lied again, "Absolutely." He was fired on the spot.