You have a small mistake in the calculus
.gauge2 .box {
border: 18px solid #0000ff;
width: 150px;
height: 150px;
clip: rect(0, 225px, 90px, 0px);
}
If you calculate the final dimensions of the box, it is width=150px + border=18px + border=18px = 186px.
So, if you want to get half a circle, you have to clip at 186px / 2 = 93px. But you are clipping at 90 px.
So, you have to set
clip: rect(0, 225px, 93px, 0px);