A tam / beret with a grid of squares / diamonds (‘bavarian stitch’) across the top.

The bavarian stitch can be done in 2 main ways: in the round or row-by-row (which works for cylinders). In both cases, it generates a fairly ridged grid of squares and the final output would be a square or cylinder of squares.

But the tam / beret needs to have a round top, so much of the challenge of this design was solving this problem.

The way the bavarian stitch is done and how it’s made of smaller squares, I was not able to have the grid wrap around a point.

The solution I came up with was to approximate a circle. When the grid gets large enough, it starts skipping the corners (the larger the number of squares on the diameter, the closer the approximation). Then have a triple increase on each sub-square corner / center to ‘round out’ the grid and also get the right number of stitches for that radius.

An additional variable is the size of the sub-squares: the number of squares determines how well you can approximate a circle, but the smaller these squares the smaller diameter. The hook and yarn thickness (and tension) impact the size of the sub-squares; so after some experimentation, I would recommend an 8 ply yarn with a 3.5 mm crochet hook. (4 mm was too big and 3 mm was a touch small for most heads).

Calculating the right number of stitches at the edge of the grid was important, as it needed to be sufficient for that radius to sit roughly flat but also needed to be a good starting point for a smooth decrease.