Reliable methods for scribing on a sphere or cone?

[MillenniumFalsehood]

Scribing on a plane is easy. I can do it in my sleep. But I swear, whenever I try to scribe on a curved surface, it turns into an exercise in frustration that ends up with lines that are not straight, not parallel, too deep, etc. I have tried so many ideas to get a good scribe on a curved surface, and nothing so far has produced good, repeatable results.

Can someone help me out with this?

[southwestforests]

Only thing I can think of right now is to design and 3D print a scribing template.

[Ant]

Old style Dymo tape is a good self adhesive 'edge' to scribe against and will follow curves to some extent.

[seam-filler]

The best results I've had for straight lines on curved surfaces is Dymo tape. It's self-adhesive and gives a good hard edge to scribe against.

Edit...

I've found this blog... http://otakuonabudget.blogspot.com/2014 ... ibing.html

[Lt. Z0mBe]

There’s a tool on Micro Mark for just this scenario. It’s literally an X-Acto blade handle on an adjustable arm. It’s with their model ship kits, as it’s made for scribing plank detail parallel to the water line.

Or, there’s the method suggested on these very forums 16 years ago to me when I needed to scribe around a propeller hub. It worked perfectly. I dipped an X-Acto blade’s shank in liquid latex and let it dry. That was to help keep it from sliding, so you could just wrap a bit of black electrical tape around it if you don’t have liquid latex. Then I took a thick, paperback book and laid it on my bench top, setting the blade at the appropriate height for the scribe via placing the rubber-coated shank as a bookmark. The blade was sticking out. Then I stacked a big, heavy stack of thick books on top of the paperback book. I simply slid the hub - pointed end up and flat end down - over to the blade, double-checked my height, and turned the hub such that the back of the blade tip was scribing a circle around the truncated cone of the propeller hub. I was making a pair of counter-rotating hubs, so they had to be scribed at multiple heights and match perfectly…and they did!

Here’s the original thread:

viewtopic.php?t=38773

I hope this helps.

Kenny

[Zubie]

Many years ago I had to paint blue and white stripes onto a propeller hub parallel to the base (||||...LS Rothman's 1/72 Pitts to be specific). I was kind of stumped because it was quite small and ogival. As I remember (this was probably 30y+ ago) I mounted the hub so I could attach it securely to my dremmel. Since it was molded in white, I just painted the hub blue and then used the dremmel as a sort of lathe motor to scratch down to the white surface to get the right set of stripes. It was a long time ago so the details are foggy in my brain, but I'm pretty sure that I made use of a dremmel speed regulator or a variac to keep it rotating at a reasonable but not unmanageable speed and probably used a glasses flathead screwdriver to do the actual etching. Came out fine.

Not sure if my hands and eyesight are steady enough to pull that off now