Change one Stretch parameter by stretching another?

[Anonymous]

I'm creating a dynamic block of a fastener. This was easy when I was creating Structural bolts that had the same thread length for a given diamter.  However now I'm creating a dynamic block of a Flat Head Cap Screw based on ASME B18.3 dimensions.  In this spec the Thread length differs different lengths of the SAME diameter.  

For this I created a Lookup that links to the Length, and the Thread Length parameter.  This block works fine if I select a size from the lookup grip, but when I want to do is stretch the length "L" parameter which will intern change the length of the Thread Length.  

Is this possible?  I've attached a dynamic block of what I have so far. 

[Richard.Vivanco]

Did you try with constraints? 

[ojuris]

you can use double lookup

[Libbya · Accepted solution]

Don't use constraints for this.  It would be much harder than necessary.  You can use either a block properties table or double lookup.  Here I show the basics of how to get the double lookup to work.  

[Anonymous]

This is basically what I need, thanks so much for your response.

I originally tried a double lookup (as I've used them to fake multiple visibilities) but I couldn't get it to work.

I think I don't completely understand the inner workings of what a DLookup is actually doing. I'll have to run some experiments. I feel I could do more if I knew what was going on.

Thanks again!

[Libbya]

The way the double lookup works is that when the input parameters on one table are changed so that they match a row, then the input parameters on the other table are switched to the values that match the lookup property of that row (as long at the other table 'allows reverse lookup'.