Measuring Objects for CAD Input

[S2kSean]

I recently measured and designed a plate for an engine to transmission adapter. It was my first CAD project I've ever done and it worked out perfectly.

Measuring and designing it was based on drawing circles for the given distances, obviously not rocket science for those of you fluent in CAD drawing but was fairly intricate for a first project. This project should be much simpler but it doesn't seem to be working out for some reason.

I'm using the same sort of method to obtain the dimensions, but I'm coming up slightly off when inputting the info into AutoCAD.

There must be something I'm doing wrong or not understanding so I'm justing looking for some help on how to measure object for correct CAD input.

If there is a tutorial or something like that somewhere I'd love to watch it, but here are my methods, maybe someone can spot my error.

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I'm now trying to design some engine mount brackets which will consist of multiple flat steel plates that will get water jet cut and welded together.

They are fairly simple, with only 4 holes.

I used my callipers to measure the distance from:

- "Bolt 1" to "Bolt 2"

- "Bolt 1" to "Bolt 3"

- "Bolt 1" to "Bolt 4"

I then measured from:

- "Bolt 2" to "Bolt 3"

- "Bolt 2" to "Bolt 4"

I also measured from:

- "Bolt 3" to "Bolt 4" 

I then used the info to draw circles in AutoCAD and what I'm left with LOOKS like the pattern I need, which is great!

However, when I use the dimension tool (to check my work) every measurement is spot on... EXCEPT one hole winds up being about 0.3xx" off of the physical measurement I took. 

I used "Bolt 1" and "Bolt 2" as constants and drew circles from them to obtain the locations of "Bolt 3" and Bolt 4".

The pattern looks good, but when I use the dimensions tool, every possible distance is good, and exactly what it should be from my physical measurements taken on the actual item.. except Bolt 3 to Bolt 4" is off from my physical measurement.

Am I doing something incorrectly to build my drawing? What am I missing?
I attached an image. Every white line between holes signifies a correct measurement. The red line is the one that comes out wrong. 
It looks physically impossible to move any hole to correct that 0.335" error, while maintaining the other distances.

(The outline is just rough to show the general shape).

[maxim_k]

Hi Sean,

If you want somebody to check constructions in your drawing, than there is not enough information in your post. We need all measurements you've made.
Axim

[S2kSean]

Hi, 

I don't so much need someone to check my work in the program, but to tell me if my methods are correct in obtaining the correct measurements for recreating the object in CAD.

In the above attached image I see no possible way that I could move the 2 bolt holes that are off closer together, while still maintaining all the other distances. I'm thinking I may have slight measuring inconsistencies that compounded over multiple measurements.

I can measure again no problem, but wanted to confirm I'm obtaining the correct information from the original part before wasting more time if I'm doing it wrong.

Attached is a picture of the engine block and the 4 threaded holes on the left are what I'm trying to copy.

You can tell which 4 based of my original CAD screenshot.

[maxim_k]

I think you have measuring inconsistencies in onsite measuring.

Maxim