Milling R/C Servo parts and horns. What material?

From personal experience, Delrin machines well. I've also seen control arms machined from aluminum for sale. However, I've read that thermoplastics move quite a bit when you machine them. The reason given was most are molded or extruded, and when you machine off the highly stressed surface you release compression on the bulk of the material.

I was wondering, how do you intend to duplicate the tiny female splines in the control arm to match the output shaft?

Pete Keillor

Ah, Delrin, that rings a bell. I will see what is available here around Duesseldorf and try it out.

Not an option (see below).

Great to know. Maybe I can get around that by milling little by little at greater distances, then come back to a part after it cooled down (imagine milling an array of 5x5).

Ah, no, luckily I don't need to. This is going to be a second, free running horn (smooth inside) on the back side of the servo, so I can mount an aluminum bracket from horn to horn, faking an axis going through the servo and avoiding the lateral(?) forces on the main servo horn.

Thanks for the help!

Tufnol is another reasonable option

Hmm, never heard of it, but my dealer sells it. I'll do some research on that. Thank you!

It's phenolic resin reinforced with fabric; available as sheet in various thicknesses (with a good finish to both surfaces) also as round and square bar. Lighter than brass, stronger than nylon and similar moulded thermoplastics. Easy to machine, cut, file, Better than ordinary (soft) Al plate if you need to tap a thread (e.g. for one of those miniature ball joints) as Al frets and loosens with cyclic loads. I've replaced things like wishbones in r/c cars with it.

Great info. Thanks a lot. I am getting a few leftover of Delrin. Do you know how that compares?