I have a pass that my great grandmother received in 1963. It states she could have ridden any train on the C&EI system except for the Humming Bird. It says she was the widow of a retired PMM operator.
There in lies the question, what is a PMM operator?
Perpetual Motion Machine ?
I don’t know otherwise - but based on the nature of these 2 answers so far, are you sure it wasn’t a position on Cal Bunyan’s railroad ? [swg]
Precision Measuring Machine operator.
In the oil field equipment business, they are highly paid and sought after machinist whose job is to measure run out, flange faces, valves, anything that has to have a zero tolerance factor or needs to be measured perfectly.
In the days of steam locomotives, they would be the guys who measures and cataloged things like bearing wear, steam valve clearances, piston ring, valve gear wear…stuff like that.
I like Ed’s response. (All I could think of was Precision Milling Machine or Pneumatic Message Machine operator - not every railyard had a tube mesage system either)
Cincinnati was the “Milling Machine Capital of the World” for a long time with names like Cincinnati Milaron, LeBlond Tool, Lodge & Shipley and others…Gave Cincinnati it’s large industrial base.
Reason I knew is because my best friend was a PMM operator for Cameron Valves.
His last job he was responsible for measuring every valve made on a natural gas well head order…these things have to be machined to almost zero variance, the pressure in a gas well head is huge, and even with a + or - 1/1000 inch variance they will leak.
His name and employee number, and the PMM #, along with any variance he found was engraved on a small plate that was affixed to each of these valves.
These valves do not have a gasket where they meet the well head, simply because there is no way to turn off the well to change a gasket if and when the gasket deteriorates, they are the primary valve installed on the drill hole lead pipe, the first valve on the well and are permanent fixtures…
Muddy one…LeBlond lathes and milling machines have a big fan base, they are collectable machines and are quite popular with the automotive build it yourself hot rod/race engine crowd.
Designed and built by guys who intended their machines to live a long and productive life, you can find both the machines and parts for them on several auction sites…neat thng is, if you own one of their mills, you can make all your own replacement parts yourself!
My local machine shop that does my engine crank and cam shafts uses a leBlond crankshaft lathe built in the 1930s…
Justin, if you have any of your great grandfathers artifacts, old journals, letters, paperwork, I bet if you research it enough, you will find he was also a Mason.
Check with the Masonic Lodge in the city he lived in last…
Question. With that close tolerances does the measurement have to be at a certain temperature and after it has sat at the temp for a certain length of time??
Don’t know about temp…I do know that these valves are built to order out of varying materials, depending on where they are geography installed and what the service is…
Have seen them built out of stainless steel, (there is like 20 different types of stainless) and what I consider regular steel, I am no metallurgist, so don’t have a clue about tensile strengths or expansion…I can tell you they range in size from a few feet diameter to ones the size of a car, from massive things to ones that two men can carry.
My friend died from MS, so I don’t have a way to question him about temps, but I do know the building where they do the measuring is a “clean room” design, he had to wear disposable booties, hair net and scrub like overall, and the actual room was keep cool with filtered air.
And after he measured them, they went to a pressure test building, located far away from the main building in what looked like an old WWII bunker, where the test guys would mount them on a test head and do a static pressure test then, run the vales through a few cycles under pressure.
According to my buddy, the pressure used was several times over the valves nominal rated value.
The idea was if the valve was to fail, better it do it there than out in the field.
I don’t know the answer but you may try to contact someone at the C&EI Historical Society. Web site is http://www.ceihs.org/index.html . I don’t know if it is still active as I think I saw something in the past about merging with the MoPac group. You still may find someone with the answer.
Ed, sounds like your PMM operator had to be a little more precise than I was with a micrometer (in one of my past lives, ca. 1969). I usually dealt with thousandths of an inch as a machinist, but occasionally went down to four figures after the decimal point. We just called those “tenths”.
Don’t know the exact tolerances, but I do know he sent one of the really big ones back because the mounting flange had a 1/1000th “dip” in it…they had to re-machine the face.
The were an ISO shop, so even if the buyers specs allowed variance, he was required to meet the ISO standard for that part.
My dad was a tool grinder for a small machine shop that did stuff for NASA. Some tolerances were to the millionth of an inch. Parts would slide together at room temp but if you held one part in your closed hand for a few seconds they would not fit. They also made the explosive bolts for rocket separation. Some areas of the shop were cleaner than an operating room but still had the oil smell. Some of the machines were very old and nothing was computer operated.
Pete
Hello all,
Thank you all so much for the responses. I like learning about my family history. I really appreciate it.
Justin