I have heard of woodturners using a black plastic (PVC?) threaded insert in place of chasing threads or using a thread cutting jig to secure a finial to a hollow form or a lid to a box. I'd like to experiment with this technique. Anyone have a source for such things? Something in the 1" - 3" diameter range? My Google search was less than productive. The brass alternatives that I have seen are priced at $25 per so I am looking for less expensive options.