So, if you want equal columns to span a div, write
<div class="col-sm-4">Column1</div>
<div class="col-sm-4">Column2</div>
<div class="col-sm-4">Column3</div>
Or, if you want unequal columns to span that same width, you could write:
<div class="col-sm-2">Column1</div>
<div class="col-sm-6">Column2</div>
<div class="col-sm-4">Column3</div>