1. Beginner - Smooth Profile

I need to make a plate that will blank off a hole left after modifying a machine at work.

The attached PDF shows my attempts so far, it's a simple 12mm (1/2") thick plate & only the holes internal to the outer profile need to be accurate to any degree.

I've tried to draw a smooth & flowing profile around these holes that will machine with a 16mm cutter but it just doesn't 'look' right, both in the drawing & in the prototype.

I'm so much of a beginner at design that I don't even have the words to describe what I'm trying to achieve, can anyone see what I mean & point me in the right direction?

2. On the two long sides, try a large arc tangent to the top and bottom bolt hole offsets. Tht'll give you one long curve instead of the 2-3 that you have now.

3. This might explain it better.

I'm trying to radius the plate around the holes by drawing larger circles around those holes. I then need to draw arcs & straight lines from these circles to form the profile.

Is there an easy way to join these arcs to the circles so that a 16mm cutter will give me a smooth profile?

4. Assuming you're using AutoCAD, to draw an arc, Use the Circle - tangent - tangent option. Drawing a line tangent to two circles is more difficult. The first example here explains how to do it.
http://jwilson.coe.uga.edu/emt669/St.../Tangents.html

5. After using AutoCAD for almost 15 years, I learned something new today. It's been my understanding that drawing a line tangent two two circles using the Tangent Osnaps didn't work in AutoCAD.

While searching this morning, I discovered that it doesn't work if you're drawing a polyline. If you use the Line command, it works fine. Since I always used polylines, it never worked for me. This is a huge discovery.

So, rather than going through the trouble spelled out in the link above, just use the Line command, and tangent snap to each arc.