Newbie, New Horn Stem Ropp Too Tight

Welcome! I’m sure others will have some ideas here, but my first thought was, how long has the stem been removed from the shank?

Did you take it apart to clean after your smoke and leave the pieces separate? If so, the wood contracted as it cooled and now your stem won’t fit.
Just my initial impression. Good luck.

A little emery cloth around tenon. A little at a time.

Rub the tenon with dry hand sop.

Rub the tenon with dry hand soap

I think sanding the tenon is a measure of last resort. Try a thin film of olive oil, or some other lubricant that may be suggested here. Note that horn, as a material, will sand-down very quickly, and that's a hazardous route to take.
I had the idea of heating the shank with a hot air blower, and if that expanded the mortise sufficiently to seat the tenon, you might try rotating the stem continuously until it seems relatively free. Maybe an expert here can weight-in on this idea.
Alternatively, freeze the stem, and try "working" it as above.
Also, consider burnishing the tight spot on the tenon with a smooth metal tool.

That's great news! Stick with the "lead" pencil trick.

Hi, jttnk, post as much as you need to do so. Nobody's counting; however, you may want to search for other threads using woodsroad's custom search in the stickies. Works great in comparison to the useless search engines on most sites.
I'm not reading in the above that you only remove the stem when necessary because each time you do the tenon wears away; after a year or two of removing it regularly, it gets loose. You can still smoke the pipe but the stem twists easily.
I don't know if this appeals but I don't feel that dissembling and cleaning the pipe after every smoke is necessary. What does this do for the pipe that can't be done with the stem in place? I run a cleaner(s) through after every smoke until it comes clean, wipe the end of the stem and clean the rim.
Rusty on Christian Pipe Smokers makes the case that deep cleaning ought be done only when the chamber draft hole closes. Perhaps extreme but gets my vote as I'm lazy and would rather not do all that work. Rusty says further that deep cleaning destroys the taste of the pipe. I never found this to be the case when I did deep cleaning, but I've yet to have a pipe sour because it has not been so cleaned, which now runs to five years.

you only remove the stem when necessary because each time you do the tenon wears away; after a year or two of removing it regularly, it gets loose.

Click to expand...

I remove the stems to clean all the time, pipes that I purchased in the late seventies are still like new.

Usually the pipe just needs some time to adjust to your environment and the problem will work itself out.