I’m having this problem when baking from one object to another. I had something similar happen several months back but it went away when I updated to 2.77. I’m in 2.78 now. You can see my bake settings in the screen grab. Thanks for any help!
Looks like it may be a problem with your object meshes overlapping. but i’m not 100% sure because you haven’t posted images of the viewport or attached a .blend
Try using edit mode to shrink the the mesh that you are baking to (Alt+S and then a small value, depending on the size of the mesh i usually use between 0.001 and 0.02)
Then double check to make sure the meshes are not overlapping in any areas.
Then set a good distance limit in the baking settings that is related to how far apart your meshes are… Like if the gap between the objects looks like its about 1 cm, i would set the distance to 2cm.
Also, make sure that you have no overlapping UVs on the object you are baking to.
Here’s the blend file…
http://pasteall.org/blend/index.php?id=44211
I’ll try your recommendations now and thanks for the reply!
No problem 
If the errors persist, i will take a look at the .blend file for you
Still not having any success. 
I will have a quick look for you when i get some free time
It’s got to be something I’m doing wrong. I think this is the same issue I was having when I posted here…
That one was fixed by updating to the next Blender version… but I bet my settings got reset or something. I must be setting up something weird that is causing this but I can’t figure it out. 
I can try appending the object into a new scene with default settings. I’m not sure I shouldn’t break this object down more and bake each piece. I’m not an expert at this but I’m trying. 
Have a look at this, it may help you…
Its a good tutorial on baking normal maps in cycles (Includes “selected to active” normal baking)
Explains cage baking too, which may solve the problem
…linky?
Lmao, sorry forgot, really busy… i’ll find it for you now
edit: here ya go https://www.youtube.com/watch?v=BPy-oNtorus
Hello there
Had a quick look at this myself,
From what i can see there is afew issues here
-You have some overlapping Geo/verts in certain areas -Which im presumming is causing the issue
-Your Lowpoly UV’s arent mapped to very well
-your bevels are far to sharp
For such a simple prop (& im presumming ur planning to use it within UE4?) i wouldnt even bother baking a normal map onto that but instead just add it within PS using Ndo for the indents and bolts but anyways i will take a closer look at this and get back to you later on when i get abit of free time.
I didn’t build this originally so don’t judge me. 
I’m trying to clean up the geometry now and get a better UV.
Thanks so much for your help guys!!
Blender seems to be not forgiving at ALL for bad geo when baking. I cleaned up the model and unwrapped it again and finally got something better but still have issues… new issues. 
Can you guys figure out what might be going wrong here?
I separated the smaller beams out and it baked fine. It has some sort of occlusion issue I guess being inserted into the main part… so it doesn’t like geometry that is penetrating. Lesson learned.
I think we’ll call this one solved.
Glad you got it sorted
If you don’t want parts on one section of a mesh baking onto another then try separating them in both high and low. It’s a simple process called exploding. If you keep the distance consistent, then it’ll make it much faster to reassemble for the finished product.
@Macser - when i use the exploding method, i use duplicates of the high and low pol mesh… that way i dont have to re assemble them after baking, as the baked maps will fit the original objects UVs that i duplicated from Saves a bit of time
OOoh… great ideas! Thanks so much guys! I’m learning a lot about this process.
@Macser - Shape key you say? 
I have never thought of that before! thanks for mentioning it… I’ll be including that into my workflow from now on!