#True position one datum free

0165(.006 size+.007 position +.0035((half of -b- size only completely ignoring the other. 067, but my -C- can still only shift a max of. I'm having a hard time understanding why my datum -B- can shift. But I've also never seen bonus tolerance on a datum really addressed in the specification. I've seen nothing to contradict what you are saying Michael. Thanks for the clarification based on what you've seen. 009 true position and measure from actual locations.Ĭonfused yet (don't worry, your not the only one)? If I get time, I will attempt to draw up a dirty print that shows what I am talking about. The 'perfect' location is the reason I ignore the bonuses from -B- and -C- in general. But remember when you measure the part, you must account measure from 'perfect' location, not from actual because you are using bonuses from -B- and -C- (even though we say we are at perfect for the above example). The hole you are measuring is +.006/-.000 so we will say it is at +.003, this gives you. However, rarely are you running at max material so we will say you are running at perfect nominal.

004), and datum -C- is a hole diameter with a tolerance of. Datum -B- will be something that aligns the part, lets say a side. So Datum -A- is the top flat surface (gaining 0 bonus). However, you add (Highest allowable tolerance-actual dimension) for each one. The secondary and tertiary features have max as well (I typically ignore these bonuses as they really complicate things and if you need these bonuses you really did something wrong). 006 + (highest allowable dimension-actual dimension). The actual diameter of the hole the feature is calling to has a true position of.

Using the following feature frame as an example: I do not have the standard handy, I am answering based on my experience. Hope everyone is having a good holiday season. This is specific to positional tolerancing for coaxiality, but shows the concept i'm after.Īs always I appreciate the help. For example a table that show the datum shift bonus is in figure 5-48 on page 144. And where, exactly, is that stated from the specification. Without complicating it to discuss multiple holes, how would the single hole be treated. Every single example the datum has a 0 tolerance. I have not seen a single example with a table showing anything where the datum has it's bonus. It should also be getting 1/2 the bonus from the -B- and -C- datums.ĭoes that mean it gets 1/2 of the.

030 from the first box of the feature frame. Īssuming the hole is at the minimum diameter. Now a reference frame for the hole(size +.006-.000) in question is.

This gives the feature a maximum positional tolerance of. 060mmc to datum A, and it's diameter tolerance is +.006/-0. 013 with the largest passing bore.ĭatum b bore has a positional tolerance of. 007mmc to datum A, and it's diameter tolerance is +.006/-0. Currently have a copy ofĪSME Y14.5M-1994 but doubt any better clarification in the 2009 standard.ĭatum c bore has a positional tolerance of.

#True position one datum free

I'll make the question clear, and please feel free to point it out. I'm sure I've simply missed the exact answer I am hunting for.