Constraining to origin with unexpected results

[ColinPearson]

Hello all:

I've managed to get this sketch fully constrained but not located in any particular location. Then somehow I broke my F.C. condition and am trying to get back there AND have it stuck at 0,0,0. I modified the sketch to its current form which included a projected origin point. I'm left with 3 dims needed and figured that constraining one point on the sketch to be coincident with this projected point would do it. I figured the distance in x, y and z would take care of the req'd 3 dims. Instead, I have two unexpected consequences:

1) When I constrain the sketch (as-is) to have 1 point coincident with origin projected point, I still have 1 dim needed, and;

2) Depending on which point I pick to constrain to said point, the sketch gets all wonky and distorted.

 

I'm really at a loss regarding 1) but for 2), I figure that it's b/c of something related to the two arcs and/or the line tangent to them. The one item missing, and maybe the way out of it is to constrain the center point of the R1.25" arc to be coincident with the left end of the horiz line that's dimensioned 2.0". This matches the example problem I'm trying to recreate. FWIW, this is for me at work; I've been out of school for many moons! The problems I get there are:

A) trying to make the two points coincident over constrains the sketch somehow, and;

B) It does allow me to dimension from that left endpoint to the center point of the R1.25" arc and make it dim=0.0". Then I can constrain any point on the sketch to the origin projected point and I'm F.C.

 

Would anyone care to comment and help me unerstand the difference between scenarios A) and B)? Thank y'all so much!

HANGER JAW.ipt

[kpyoung333]

A good practice if you get crazy with constraints is to select everything, delete all constraints. Project Geometry on Center Point from Model Tree. Set all vertical lines, set all horizontal lines, set tangent constraints. Your dimensions should stay the same but give you more simplified constraints. An easy way to check before setting the coincident origin constraint is to select any corner, Fix (lock icon), show degrees of freedom. This will show you if it might go bonkers. Simply undo the Fix, then set coincident from Center Point to where you want origin (center of the circle) and should jump in place without getting skewed. If you still have issues, delete sketch, start over! I almost never use my first sketch when designing, make something quick and ugly, figure out which dimensions/constraints are key, redesign with those in mind. (sometimes it will show "1 dimension needed" but is just an error and is actually fully constrained, may need to close and re-open program) The only thing I see in your sketch that is "bad" is you have a vertical constraint from the bottom circle endpoint to the center point instead of tangent to the .75 dim. and a .5 dim for the top circle instead of a tangent - perfect example change the top circle to 1.5 then see what happens. Unless you have a d52/2 relationship that .5 dim is going to cause problems.

[ColinPearson]

I don't know how that constraint got in there. Thanks for taking the time to offer your help. I'm pretty good at AutoCAD, been using it near-daily for about 15 years now. I know that IV is vastly different, but I'm really trying to understand it as I go on a level mroe like how well I know AC... that means progress appears slow, but along the way I'm finding where all the settings are that I'll need, etc. Really helps to have a couple pointers here and there