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| Chuck in E. TN:
I know this has been posted before, but I can’t remember where. I’m studying plans for my next engine project, one of Elmer’s’ Wobblers. The drawings have dimensions like Ø3H7, or Ø12P7. I forgot to save a link or print the page that explained these dimentions. Can anyone help? Chuck in E. TN |
| Bernd:
Chuck I have Elmer's book. Which engine is it. If you don't want the public to know PM me. Bernd |
| PeterE:
Hi, The dimensions are shown with tolerance. The first characters, the diameter sign and the number states the diameter, f ex dia 3 mm. The next part (H7) states the tolerance of the hole or axle. If I remeber my mechanics correctly, the a captial letter "H" states the hole, and a minor letter "h" states the axle. The numbers following tells how large difference from "0" to be used. 7 is an ordinary sliding fit without any shake. A far better explanation and illustration is found on this wiki page: http://en.wikipedia.org/wiki/Engineering_tolerance Hope it helps. BR /Peter |
| Lew_Merrick_PE:
Chuck, http://www.roymech.co.uk/Useful_Tables/ISO_Tolerances/ISO_LIMITS.htm has posted links for both hole and shaft size values for each class of fit. If you think of it as being the old ANSI/SAE fit class (Shrink Fit, Press Fit, Transitional Fit, Locational Fit, Sliding Fit, Running Fit, or Clearance Fit) tolerance, it will make a bit more sense. The problem is (as always) that such a tabulated approach is fine for non-interference fits at moderate temperatures, but not for interference fits at moderate temperatures for non-basic steels or for any application out of the nominal 20°C ± 20°C range. If I seem a bit anal retentive about this, I am. I spent four months in the mid-1970's compiling a proposal for a modification of the ANSI/SAE fit standards as part of an ISO simplification effort. Instead, the committee decided to continue using the data that was compiled for the Spanish-American War and WWI as the basis for the "standard." |
| Chuck in E. TN:
Bernd, It's Elmer's #25. Chuck in E. TN |
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