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... I learned something today from a younger-than-me old timer. Here it is ... when holding your micrometer (as shown in the pic), the longer you hold it, the shorter the part you are measuring becomes. Here's why ... the mic heats up where you are touching it, making that particular area of metal expand, carrying the spindle with it, making the part you are measuring seem a couple of tenths further away. The part didn't change, but your micrometer grew 🙌 Why was it a lesson to me ? Cause I never stood around holding a mic like QC folks do, thus I was never exposed to the phenomenon 💯 ML
546 likestopshotdustin Verified 😮
simon.deffner This is why the measuring Lab uses vises/clamps for the micrometer when checken Lots of parts. So only the spindle end has to be touched for usage. 4 likes
ohio_outcast QC guy here. I can see this gentleman's point, but I've never had my mics in my hands long enough for that to happen to me 1 like
- laruetactical @ohio_outcast ... Same here ... or maybe it did and I just didn't catch it😎 2 likes
usgeneral25 Always something new to learn?
300blackout_ Dang!!!
arrowheadrifles Part grows here in Phoenix 😂
charliesclones Maybe your parts are just so hot 😰 😂 1 like
hunter47525 😂😂😂
lost_soul12151791 Good to know.
the_red_rhino Interesting. I never really considered this before. Funny because I have a precision measurement test coming up and I wonder when the answer key was made. Winter? Summer? Verified the day of?
romeo_hotel_engineering That's why every good machinist needs an oven mitt in their toolbox
- gevas.defense.gunsmith @romeo_hotel_engineering they blocked your comment for being offensive ?
scvdannyboi Here's another tidbit, the black plastic portion of that mic is meant to insulate from the heat. Bigger mics might have holes in the body, also meant for dissipating heat. 1 like
- breedlove.ben @scvdannyboi and reducing weight. I had a 24" mic at an old job that tool would be too heavy to use without the relief cuts 1 like
bklingensmith61 True but depends on conditions in the shop. Climate controlled temps I can understand the changes. Factory conditions, 90-110 degrees daily, not gonna make a difference.
- laruetactical @bklingensmith61 ... Factory temps of 110 degrees are only found in foundries ... 😳🔥😳 1 like
- bklingensmith61 @laruetactical and vinyl extrusion plants. Our plant averages that in the summer and we use both calipers and mics. Not fun but it's a living.
- okie_gunslinger @laruetactical I beg to differ. I work in the curing department of a tire factory and in the summer it will be 110+ behind the presses and the department will be 95+. 1 like
- gl622 @laruetactical my laser cutting shop hits that in the summer lol
- i_got_it_all_worked_out @laruetactical Also in my pants.
- ohio_outcast @laruetactical nope. I've worked in shops here in Ohio that get that hot in the summer. No AC, no ventilation, and no fans. It was a boiler room
mr_20k_man That is why my uncle never let me hold the micrometer with "monkey paws". Those lessons were LONG ago, but now I get it! I just accepted his directions because he was a machinist turned gunsmith. 1 like
cdm_gear Air or demitron gauges are a better choice over a telescope gauge and micrometer. 1 like
teamtomlyn Wow solid advise! That guy is a keeper
briangreen9050 Most you're gonna see is .0001 or maybe .0002 max unless you're hands are on fire
- laruetactical @briangreen9050 ... Yep, and we were seeing 0.0002" 1 like
- briangreen9050 @laruetactical grinding ODs on pins in the same way. Gotta wait for them to cool down completely for an accurate number. The company I work for makes precision molds and surface grind quite a bit. Some tolerances are + or - .00005. Most need to be within .0001 square, flat, and on size
dmcwilliam.762 Back in college I took a tour at a Navy metrology lab. They showed us a height gage sensitive enough to show thermal flex if you put your hand NEAR the post. Also some old bore mics for measuring 16" guns and a surface plate big enough to park a 40' RV on. Cool stuff.
- laruetactical @dmcwilliam.762 ... That's a helluva surface plate 😎 1 like
breedlove.ben I spent a few years as a QC guy and yea it's true. Not a huge difference but it can add a hundredth or two
- breedlove.ben @breedlove.ben thousandth* mis-typed lol
just_really_b0red It's good to learn at least one new thing every day. Bravo.
robby.baldridge So you're saying you need to not set the micrometer down all day and have it calibrated at that temp
- okie_gunslinger @robby.baldridge high end QC on parts with extremely tight tolerances will use a fixture that holds the mic so that body heat is not transferred to the spindle. Also in some settings ambient air temp is tightly controlled to specific tolerances and that part will have to be away from the machining operation to come back to ambient temp to help eliminate variance in measurements from temperature induced expansion or contraction. 2 likes
- robby.baldridge @okie_gunslinger yeah most true QC metrology rooms are very tightly temp controlled. Hell we had a lathe part that the only way we could consistently hold tolerance was to let the lathe spin at the RPM the part was turned at for 2 hours so it was all up to temp when it was making parts. 1 like
- okie_gunslinger @robby.baldridge damn that is insane. I am just an ameture machinist at best (had to learn it in industrial maintenance school) but the tightest tolerances we ever had to hold on class projects was +/- .002. 1 like
- okie_gunslinger @robby.baldridge but because of that class I got really interested in metrology and love watching YouTube videos about it. It is fascinating to watch someone lap a surface plate or scrape the ways on a manual lathe to beyond .00001" of flatness or better. 2 likes
- scvdannyboi @okie_gunslinger now you're talking measurements in helium lightbands 🙌
- okie_gunslinger @scvdannyboi from what I understand when a granite surface plate is being lapped depending on the grade flatness is measured in arc seconds and a Triple A grade laboratory surface plate will have a guaranteed flatness with 0.000001" variation across the plate.
greatdayfor2a Thats why you get the protective boot for them helps mitigate that
cvmn66 Yep, try to do an alignment on a motor that sits in the sun. You got 2 or 3 out at 8 am go to lunch and the all the numbers for your almost alignment go to hell hahaha
kenny9596 I work for a metal manufacturer.. I "hot mic" material after its been through the rolling mill.. it's crazy to see how many thousands the mics opens up especially with larger micrometers in the 4-5 inch range putting it on a 2000 degree piece
hurr_durr_derp Yep, I have this exact experience when I have to measure a batch of parts. After a couple of minutes in I remeasure a standard to know how much to compensate. We are making parts with micron tolerances though so it may not matter to most.