[whartung]

Not just regular ball point pens, but with a rather long tip.

You take a modern, generic Bic pen, and the tip is angular. It's a cone shape, ending in the ball point. The Spirograph pens had their ball point at then end of a tube that was about a 1/4" inch long.

I can see if someone pressed really hard, at an angle, how you could bend or break the tip. But it was perfect for Spirograph, because it just went straight in, and was strong enough to drive the gears.

I can see how using modern felt pens may be the modern, common (as in really easy to get off the shelf pens for) solution. But, a felt tip us not a ballpoint and could suffer different issues working with something like a Spirograph (such as splotching).

And stay away from gel pens, what a smeary mess that must be.