Needle sizes & When to use large hook needles.

Typically, there are two different types of needles. Cylinder needles and ribber needles.

The cylinder needles are the long shank needles. This is a photo of a 12 gauge cylinder needle typically used in Auto Knitters, PT Legare's, most Creelman Brother's, Master Machines & Verdun's:

Cylinder needles essentially makes knit stitches.

The shorter needles are ribber needles and are used in a ribber dial. Ribber needles purl. Here's a photo of a 12 gauge ribber needle:
Pat Fly with Angora Valley is currently the resource most CSM'ers use.

Pat also sells needles called Large Hook needles. These needles are exactly that, larger hooks.

Why use a Large Hook needle? When you have a machine that can handle thicker yarns (I've heard some LeGare 400's can knit worsted) or if you find that your yarns keep splitting.

I personally have an Auto Knitter and my machine, while it can knit with the large hook needles, it's certainly not happy (i.e., it feels very different when I crank and tends to drop stitches more often).

On the other hand, I've heard from people who one LeGare's who LOVE the large hook needles.

Another CSM'er likes to use large hook cylinder needles and regular sized ribber needles.

So really, it's a matter of what you're machine is happiest with.