Do you have to nail them in? I usually just shove them back in place and rely on the paint film to keep them there.

I have a few places where earlier restorers (pre-1880's) broke a few when they changed out the small light sash for 2 X 2 (darn it!) and broke or cut a few of the orginal parting beads. The smaller pieces were nailed back in, and the rest are just held in by friction (but still need a lot of mojo to get out). I am not pleased when I run into the nailed sections.

L

A small finish nail is all they need.

I usually put them at the top and bottom, but far enough from the ends to eliminate any chance of splitting the parting bead.

A gun driven nail is better for reducing the chance of hammering causing any damage.

I don't have a nail gun.

I know I need small finish nails. I am asking where to buy them. When I nail shop at HD, the 1.5 inch long nails seem too thick to use in a parting bead.

They sell them at HD. If you can't find them, just ask. Tell them you need finish nails for a woodworking project.

If you don't have a nail gun, that is fine. They obviouslt didn't have nail guns when they were putting that window together originally. To prevent splitting, you can predrill a hole in the bead slightly smaller than the nail.

My parting beads aren't nailed in either...just fitted in and held by friction. I haven't broken any yet, so I don't know if new ones would be the same--but if the new ones are the same dimensions, it should fit the same way.

Buy some 1.5" stainless 18 ga. brads. Not bright steel, not even galvanized.
It's correct that they were a friction fit originally. Any nails in the bottom 1/3 will make it a bad job for the next remover of the p-beads. Nail sparingly.
Casey

Well, heck, if I don't have to nail them in, I'm not gonna!

Personally I would go to a lumberyard get 1 1/2" brads and a had brad driver and just push them in. While originally friction fit a couple of nails will insure that they will not fall out.