How common is this ?

[compact8]

Just today it happened again. I intended to cut out an aluminium strip of lengthen 47 mm with hacksaw and after some further machining, I found that the lengthen of the strip was 42 mm instead so I had to redo it from the very beginning. The error was due to reading the scale on the ruler wrongly. My focus was on counting the 2 small divisions after the longer scale marking but I did not realize that the longer marking represents 40 mm instead of 45 mm. The same problem has occurred when reading the X Y scales on my mill and those on hand wheels. Installing a set of DRO has eliminated the problem but I am still having troubles in reading scales. Just wondering how common this problem is.

 

[jwmay]

It all depends on how shiny the scale is, how much light I've got helping me, and just exactly how small those teensy little divisions are.

 

[SLK001]

The saying is, "Measure twice, cut once..."

More realistically, it should be, "Measure once, cut once, weld it back together, measure again and cut again. Repeat as needed."

 

[mmcmdl]

The saying is, "Measure twice, cut once..."

More realistically, it should be, "Measure once, cut once, weld it back together, measure again and cut again. Repeat as needed."

Sometimes this doesn't even help .

Way back in the 80s , I had a very large job for NASA going on . Spaceflight parts for a satellite . This was a grid made in 4 identical pieces , all 4 had to be fully ground on fixtures and were approximately 4 foot long . We were making 20 grids . Had angles and holes , wire guides , flatness specs etc . The whole list of certs ect . The final operation was I had to grind the final overall length dimension to within .001 . I made a reference grind cut on both angles , took the part into our inspection department , and they gave me what the part measured on paper . They gave me the vernier calipers to use and of course they were calibrated . I dialed half the distance of the difference on the SG and ground it off using the diamond wheel , flipped the part , and ground it to size . Overall length was perfect . Took it in to inspection for first piece signoff stamp . They signed off . Next few weeks I finished up the parts , they were inspected once again and delivered Nasa . 2 weeks go by . SURPRISE !

All parts were .800 too long , to the .001th . Our inspector read the ID scale on the verniers and NOT the OD scale . If any one of us in the process would have checked with a tape measure we would have seen the issue no problem . Everyone on the job was looking at the .001 and overlooked the obvious . I had a little extra work for a week as a result . In the end . everything was cool . I have the surface grinder that these were made on in my garage which is quite a story in itself . If you've never worked with MaCor , it's a real treat . It will crack in two before it'll bend a thousandth .

MACOR Machinable Glass Ceramic | High Temperature Machinable Glass Ceramic | Corning

MACOR machinable glass ceramic is a solid, trusted foundation that can help you realize your designs quicker.

www.corning.com

 

[jwmay]

Making a die holder a couple days ago. Ran the boring bar 364" deep and out .350" on the diameter. Stopped to check measurements. Calipers read .274" deep. So I bore it .100" deeper. Stop to measure...stills reads .274". Maybe my toolpost is turning? Another .100" deep. There we go. .375" deep, finally. Gosh that looks quite a bit more than 3/8ths". Dropped the die in. And there we have it.

 

[C-Bag]

Maybe not exactly the same, but very similar :

Mars Probe Lost Due to Simple Math Error​

Mars Probe Lost Due to Simple Math Error

NASA lost its $125-million Mars Climate Orbiter because spacecraft engineers failed to convert from English to metric measurements when exchanging vital data before the craft was launched, space agency officials said Thursday.

www.latimes.com

 

[strantor]

Couple of weeks ago I was cutting unistrut for my saw project. I hate cutting unistrut. I use it and re-use it for all kinds of projects. Take that project apart when I've had my fun with it and make something else. I'm basically a 200lb adolescent playing with erector toys. So cutting it makes me cringe because that's one less long piece I'll have for the next project. When I do cut it, I try to cut it into 2ft, 4ft, or 8ft pieces. That way the holes at least still line up. I needed two pieces 56" long and there was no way around it, I had to make cuts.

So I got an 8ft piece, couldn't find my tape measure so I used a 4ft ruler, made a mark, moved it over 8" and made another mark. Took my bandsaw and cut on the 48" line instead of the 56" line. Cussed myself, grabbed another 8ft piece and did the exact same thing again. Cussed myself and threw my marker into the abyss. Grabbed a brand new 10ft stick and made my marks with a scribe since I didn't have a marker anymore; this time I scrawled a bold "YES" and "NO" beside my lines in maniac font, grabbed my saw, made my cut, went to put the piece on, and it didn't fit. Measured it, 56" on the nose. Re-measured where it needed to go; 58" is what I needed all along, not 56". Cussed myself, realized that having now cut it 56" instead of 58", I wouldn't be able to get my two pieces out of that one 10ft stick and I'd have to cut into yet another piece. Cussed myself again, turned the lights off and walked back to the house with my tail tucked. I consoled myself with thoughts of "you're not really that stupid, you're just tired. You need to rest. You'll be smarter tomorrow."

 

[jwmelvin]

[mention]strantor [/mention] that’s a fabulous story and I’m sure I’m not the only one who can relate. The self loathing can be strong at times.

 

[DavidR8]

So many times I've done that!

 

[Dan Krager]

I just found out that a beautiful stack of 13 twelve inch capacity hand screws I've been working on won't "crank". I threaded the LH and RH rods incorrectly and to fix it will have to redo half of the rods. The wooden jaws are ebonized and oiled oak that I've been hording for almost 40 years and the custom handles are a London pattern which I make for all my wooden handled tools that need new handles. The brass ferrule are made from 3/4" brass hex rod. Will have to get pictures after lunch. It was a long and nasty learning curve how to thread long rods in a hobby shop. Now, if I can remember, I can put that knowledge to good use....

Go configure.
DanK