Does anyone know of a manufacturer which makes an adapter that connects a 1/8 nptf male tube adapter to a standard zerk type grease fitting? This is for a automatic lube system for a Semi.

If you want a device to connect an auto lube tube to an existing fiting I believe you will hava a more reliable setup if you replace the zerk with a direct connection as it will be less likely to let go under the dynamic conditions of an operating semi. Lincoln, Alemite and other grease system manufacturers will be glad to help you design a system to work in your application. You should be able to find much information through a web search on grease systems.