This is an exploded view of a basic displacement lubricator.  The hole in the steam pipe is located about 3/32" below the bottom of the cap.  The drain is very handy and doesn't add that much work to the project.

You could also buy a ready made lubricator from Roundhouse or Sulphur Springs Steam Models.
The parts were made from K&S brass and copper tubing as well as some flat brass strip.

O-rings were purchased at the local hardware store.

The drain and cap are made from brass machine screws (coarse pitch for easier starting of the threads).

The female portion of the cap was turned down from a brass nut.

The female portion of the drain was drilled and tapped from a piece of brass rod.

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All content presented in these pages is for informational purposes only and does not constitute an endorsement or recommendation of any particular technique, component, or design practice. It is up to each individual visiting this site to research and decide for themselves the suitability and safety of any techniques, components, or design practices they may wish to employ in their own practice. You - and only you - are responsible for your safety. When approached correctly, building and operating live steam locomotives is a safe and enjoyable hobby. There are many books available in the hobby that can guide and educate the novice. Check with one or more of the online live steam discussion groups for recommendations.