Thought I would share this with the forum. Many have the cheep little chain tool mine was under 10 bucks at my LBS. They work pretty good for pressing out a chain pin. The trick is to stop short of pressing it all the way out if reassembly is required at some point and for me that sometimes works or for some other reason I'm needing to reassemble a chain where the pin is all the way out.

I made this little gadget I'm sure others with a little skill could duplicate and it worked quite well. The gadget is a barrel that has a drilled hole that is a close slip fit with the pin and outside and length to suit your chain tool. Also a drill bit that’s a close slip fit with the chain holes. See attached photos.

I use the drill to line up the chain and also it can come in handy to lightly ream out any burr or crud in the holes by hand. I place the pin in the barrel and drop it in the tool, then the chain put a little light pressure on the pin and make sure it looks lined up (second photo) and then slip the barrel up to meet the chain and screw the pin into the chain, the barrel holds the pin straight. With mine I can get it in about 3/4 before I run out of travel. I unscrew and remove the drill and barrel and finish pressing it in.

I'm sure there are many better tools for doing this but this works for me and is light weight and stays in my tools that go touring. Hope this helps someone out.

Clever tool to bail out if you do press the pin too far out. Some chain tools (Park's CT-3 for example) have a travel limit stop to keep you from pressing a pin all the way out of the chain's sideplate for chains with reusable pins.

Also, all modern 7/8-speed and above derailleur chains must not have an original pin reinstalled whether it's pressed partially or all the way out. The old pin must be removed and replaced with a specific joining pin or a master link.

Good input. I should have mentioned master links and replacement pins as well. Sometimes sitting on the side of the road you have to do what you can to get underway, and to a bike shop. Shortening your chain a link and avoiding the big ring will get you moving at least, or if your rear derailleur fails maybe a lot of links to make it a one speed. Or walking L

This chain sample shown was actually off a 9 speed cassette and for sure don’t reuse any pins against recommended practice for long term usage. Without some lineup means it is virtually impossible to re-insert that pin on the road.

modern 9 and 10 speed chains are fussy you may get away with more on 7 speed chains.

but the riveting of the pins keeps them from blowing out.

you stretch the side plate pressing it out. then realistically,
the head has to be expanded further

If you don't force shifts, after this field fix, it should get you back to a town..

on the road cures are temporary, replace the chain ASAP.

with practice , you learn how to press the pin so as to remain in the last plate,

ideally leaving it just a scosh proud, so the inner link would snap over that nub.
and stay there while you press the pin back in.

Nice idea, but I'd rather carry a master link with my chain tool. Like others have said, modern chains shouldn't be re-connected with the same pin, so drive it and the adjacent pin on the outer link completely out, and install a master-link for a permanent fix.