Dimensioning Question

[TomG]

(12-10-2014, 08:16 AM)Mayhem Wrote: Tolerance is still something that I am not fully comfortable with.  I must admit that when I watched Tom's latest videos it seemed very strange to hear him say a part was -0.000 and +0.003 and so he was aiming for something in the middle.  Even stranger to hear him say that if the dimension was only to two decimal places he wouldn't even bother to take a final measurement.

Of course, having him explain why made a lot of sense but it just seems strange when I have been trying really hard to nail a dimension exactly, when in hindsight, I probably didn't need to worry.

That's really good to hear Darren. Part of good design is to make use of tolerancing in a way that makes the part easier and less expensive to make, but still meets it's intended purpose. That's why some of the dimensions in the knurl holder, such as the length are two place, and the slots, outside dimensions and hole which mate with other parts are three place, or three place with an attached tolerance. For instance, if a 1" thick part has a general tolerance of plus or minus .005" and you spend extra time machining it to within .001", you have wasted time. If the part was properly designed, it will work just as well at 1.005" as it will at 1.000". Capisce?

A video on the application of tolerancing is one of the topics on my list.

Tom