I am looking at designing a rack and pinion system that will be laser cut out of some plastic. While the cad system that I am using has a spur gear generator, I was looking at the design of the rack gears. I thought that it needed an involute type profile, but many of the references that I see have a flat profile instead of an involute type profile. For example, this metal rack gear from McMastercarr has a seemingly flat profile.
Is this common? Is the reason that it has a flat profile due to the fact that the radius of the base circle for racks is theoretically infinite?