Timeline for How can I measure a length of over 4 feet to an accuracy of 1/100th of an inch?
Current License: CC BY-SA 3.0
13 events
| when toggle format | what | by | license | comment | |
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| May 23, 2015 at 16:11 | comment | added | Ambrose Swasey | @Photon The first problem of physics is to measure the physical world. | |
| May 23, 2015 at 16:10 | answer | added | Ambrose Swasey | timeline score: 2 | |
| May 23, 2015 at 7:46 | comment | added | DanielSank | I agree with everything @Floris has said/asked. We need to know what tools you have available before we can recommend a method. | |
| May 23, 2015 at 4:39 | comment | added | Floris | Unless you tell the experienced metrologist exactly what tools you have available I am not sure anyone can help. Clearly you are missing the tool to measure this length directly, right? 1/100th inch is 0.25 mm - it ought not to be hard with the right tool. What is the greatest length you can measure? | |
| May 23, 2015 at 4:36 | comment | added | Ambrose Swasey | @Floris It's not the simple. I need an experienced laboratory metrologist to answer the question. | |
| May 23, 2015 at 4:03 | comment | added | Floris | What is the longest bar you can measure with your available tools? How big is your micrometer? If you can grind a 6" bar to a precision of better than 1 thou, a stack of 8 of those will measure 4 feet with better that 1/100th. | |
| May 23, 2015 at 4:00 | comment | added | Floris | @TylerDurden when you machine steel it heats up; you want accuracy of 0.01 in 48 or 1 part in 5000. Coefficient of thermal expansion is about 1 part in 100,000 /K - so if the bar heats by 20 K it would use up all your tolerance. When you cut steel it can easily get much hotter. Worth keeping in mind, at least. | |
| May 23, 2015 at 1:40 | comment | added | The Photon | This question might be a better fit on engineering. Even better would probably be a Machinist's stack, if there was such a thing. | |
| May 23, 2015 at 1:27 | comment | added | Ambrose Swasey | @docscience Cast iron moves about 1 tenth over 5 feet, so temperature is complete non-factor. Cutoff tool, LOL. | |
| May 23, 2015 at 1:21 | history | edited | Ambrose Swasey | CC BY-SA 3.0 |
added 13 characters in body
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| May 22, 2015 at 23:49 | comment | added | docscience | I suspect also to maintain that type of accuracy you would need something like a laser interferometer or inductosyn fit to your cutoff tool. | |
| May 22, 2015 at 23:47 | comment | added | docscience | At what temperature? Temperature will be a factor over this distance. When you machine the bar (however you might be able to do this) you need to keep it at the temperature you define the length at in order to keep 0.01 inch accuracy, unless you are making the bar out of invar. | |
| May 22, 2015 at 22:34 | history | asked | Ambrose Swasey | CC BY-SA 3.0 |