The Jalopy Journal
Discussion in 'The Hokey Ass Message Board' started by blowby, Jan 17, 2020.
I have one for truck brake drums, one small one (6") and the rest are digital (4)
I like the digital because you can go metric with the touch of a button.
I have 5 dial calipers, 3, 6" & 2, 12". I keep them in the basement work shop, the outside garage, and the under house garage. that way I have them where I need them.
I have a 6" HELIOS dial caliper that I bought used in 1970 when I was a tool and die maker. That was 50 years ago! I never quite made it into the digital age except for my flip phone and this derned computer.
6" Mitutoyo for me!
Little story: I was machining some aluminum castings that had four holes drilled and reamed on a very large 5 axis milling machine. Two of the holes were about 2" deep and the other two were 4" deep and were reamed to finish size. The same reamer was used to finish all 4 holes. There was a .0002 (two/ten thousandths) tolerance. The holes were for steel pins to be pressed into place, and the .0002 tolerance was overkill for a simple interference fit. As the reamer did its job, one of the deeper holes (they went all the way thru) would drop slightly out of tolerance as it got deep in the part. It was dropping about 1/10,000th. Thats small enough to be negligible in the environment we were working and inspecting in. There was no way to adjust it, because it would then go out of tolerance on the other holes. The inspector wrote the part up. We had a "discussion" about it and he refused to budge and OK it. (An engineer would then eventually have to approve it, as they would not scrap the part anyway)
I held on to the part for a few days until I started a new "lot" of parts. When I took my first piece up for inspection, I substituted the one the inspector had written up. He inspected it and approved it. Then I took the inspection record from when he rejected it and pointed out to him that it was the same one he had rejected previously.
He was pissed !!! He reinspected the part checking every other dimension and trying to find a variation to prove it was a different part......but it was the same part so he had no luck.
Now normally this guy was a very good inspector who took pride in his work. My point with this story is that when you start inspecting precision parts and dimensions you rely on the quality of the tools you have available, and even with professionally calibrated and maintained guages.......there still can be a human factor involved. Very very expensive inspection tools usually remove as much of the human factor as possible......but they are usually working much closer tolerances. Big Chief hit it right on the head with something I failed to mention. The guage you are using needs to be much more accurate than the tolerance you are holding. So does the machine that you are using.
Thats a great rule of thumb. If you are trying to hold .001 tolerance you want a guage that can check in .0001.
If you are working in .0001 (.0005) it would be great to have something that could read .00001 increments. That last increment is beyond the scope of home builders, so we are then limited to the .0001 that a micrometer can provide.
Normally that is more than sufficient for anything us amatuers do.
I hope this provides a little insight into the use of micrometers and calipers.
Note: All the other parts run were run with the same reamer and no adjustment.....so if one was bad, they all were bad.
Guess they can't put metric on the dial, like a speedo, since one rev is .100".
yes every day at work, as said needs no batteries.
Ekimnierbo, one part of your post brought back memories and a chuckle! Back in the seventies , while looking for a job, I found one in a production machine shop where we made many of the same parts every day. The tolerance on parts varied, some +-.001, some .005, some .015. The last we used yardsticks for measurements ! Lol
But all parts were inspected..... and I like you didn’t want any of my parts turned down. Several times I resubmitted the failed part, and it passed the second time! I never told the inspector! I think she just wanted to justify her job!
Thanks for the memory and chuckle!
Cant afford one...........still using tape measure.
I have one of each, and an analog mic at home, but at work it's all electronic. In all fairness most of the temps we get are window lickers so we have to eliminate any possible f-ups that we can.
In my first (industrial) machinist job out of trade school my leadman told me something that while not totally accurate still makes me laugh.
"The only difference between an apprentice and a journeyman is the journeyman knows how to hide his f#@k ups".
All the time. I have a 6 inch SPI and a 12 inch Kanon. Both are great. Have an old Mitutoyo vernier from 1981.
Sorry BOB, magnifiers are not an option, I wear the 2.5 visor frequently now. On top of prescription readers..the golden years.
Your "in and out" example could very well have been temperature related....especially with aluminum parts and the amount you were out of tolerance. If we have the time.....we try to bring tight tolerance parts into the lab and put them on the surface plate or CMM stage for 24 hours to equilibrate before we start working with them....then its gloved or soft tool handling as little as possible.
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Digital at home.
Automated lasers at work. Those make no Human errors.
4 pages in three days and we still don't know why the OP asked the question. Only on the HAMB.
Production, liked laser measurement on crank runout.....statistical quality data requires such...
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A clue. Do you ever feel alone?
The dial ones will die kids anymore can't even tell time on an analoq clock.
Not because I grew up with only dial style clock's, they and analog dash gauges give me a better since of time and space over digital.
A good dial caliper was one of the first precision tools I purchased. I use the digital caliper for reloading where ease of reading and reasonable accuracy are the priority. The simple slide caliper works fine for most odd jobs around the shop.
That's what I use too Bob, I don't need no high falutin dial thingy.
Post #11, or is that too much to figure out?
ekimneirbo and BigChief are obviously old school machinists, believe them.
BigChief mentioned how temperature can affect measurements. Working in manufacturing many years ago, I found myself doing QA on small centreless ground inner sleeves for needle bearings, using Federal snap gauges. The more you handled a small part, the more it warmed up and the larger it would measure. We're talking tenths and hundredths here.
I'm a geezer, I learned on vernier and dial calipers, still have them and occasionally use them for scribing or dirty locations. I use my digitals almost exclusively every day for measuring. Jeez, all this talk about dead batteries. If you buy cheap dollar store batteries, they won't last. If you leave your tools on overnight they'll run the battery down quicker. I put new name brand batteries in my Mitutoyo digital calipers about once every two years.
I like being able to set zero anywhere:
-Lets you measure down from a machinist's rule to measure a depth- zero at ruler width, use the ruler to bridge a gap, measure depth directly.
-Set zero at a desired dimension, then you can measure plus or minus.
-When turning a part on a lathe, zero the caliper at the desired diameter, measure to determine how far you have yet to go. No mental math required. If turning a critical diameter like a press fit, I get close with the vernier then use a mic.
No caliper of any sort can measure tenths accurately.
Keep your measuring tools clean and dry. If you drop them and bend the points, the accuracy is gone. In the absence of a set of gauge blocks, a ball bearing makes a good "standard". The races are ground to very tight tolerances, look up online the inner and outer diameters and width of a bearing you have on hand, measure the bearing with your calipers, see how your measurements compare to the manufacturer's specs.
Moved up to a dial caliper from vernier a while ago, still haven't found a reason to go digital. I have to put on glasses to see the vernier scale these days, but I can still see a dial ok without them.
My mill has some really old Bridgeport optical scales on it, like DRO only better (it's analog!)
I use the 6 inch Mitutoyo that I bought in the 1970's quite often.
Have a 4" and 6" Mitutoyo, and 1", 2" and 3" Starret Mics, as well as a couple of pair of good Verniers...
Still grab the HF Digitals 9 times out of 10.
We still teach apprenticeship students to read dial calipers and micrometers and other fun measuring tools....most of them use digital at work
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Yup, Uncle Sam doesn't believe in that new-fangled digital stuff!
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