Look at Park Tools and at the tool board of any reputable LBS and you will NOT find a pipe cutter for steer tubes. They simply are NOT used. Think about it, pipe cutters are fast and make a nice square end edge, so shops would use them if they were the right way to do it. They are not. You MAY have cut yours successfully, but trust me, this is NOT the tool to use.

Pipe cutters do two things to metal tubes: They cut by pressure, manually manipulating the metal, which increases the diameter of the end of the tube as they cut as well as put a round protrusion on the inside edge of the cut. The pipe cutter cold works the metal as it cuts, so doing this to aluminum, and especially heat-treated aluminum is simply a bad idea. Installing a star nut, or other fastener will be difficult or impossible unless you re-size the inside edge. But more importantly is what a pipe cutter does to the top 1/4" of the tube. You may have difficulty fitting headset spacers and the stem over the top of the tube, which would require resizing the OD. This SHOULD be done on a lathe, but who would do that? Instead, the average mechanic would use a file to get the proper OD. This obviously introduces all sorts of inconsistencies to the tube diameter. Not what you want when depending on stem clamps to maintain headset bearing preload, and secure fit.

And obviously, carbon cannot be cut this way.

So to anyone reading this thread, the industry-approved way to cut tubes is with a sharp hacksaw blade, cutting oil and a guide. A file is then used to finish the end and chamfer the inside and outside edges. A Dremel can be used as well. A grinder can be used, but with caution because it's easy to remove too much material and affect your final cut length.