I have an 1890 Elgin grade 97 watch that needs a new roller jewel. The problem is the hole on the balance staff is round and all I can find are "D" shaped jewels. Can I fit a "D" shaped jewel in a round hole? Will shellac fill the gap and hold it? Any help would be appreciated.

Yes you can use a D shaped roller jewel. Measure the fork in the pallet so you can select the right size. The flat goes toward the outside of the roller table and shellac will flow to the void. The jewel must be perpendicular to the roller table in all directions with the flat not turned to favor one side or the other.

Thanks for the help Roger.

It may be easier to look for a roller table that is the same size and swap out the tables but remember, You must first be sure the new "D" jewel will fit the forks.

Probably one of the more important skills to learn is shellacking jewels. Old shellac is notorious for allowing jewels to loosen and I check the roller and pallet jewels on every watch I service. The frequency of finding a loose jewel...especially roller jewels is very high. The jewel may move a very small amount...almost imperceptible, but that movement translates to loss of impulse force and less amplitude and poorer timekeeping.

Roger is right! He checked the jewel on the last watch he did for me, and showed me the slight movement of the jewel. I would not have noticed it on my own.
Roger also shellacked it without leaving any shellac showing around the jewel!

Also John just be careful with the heat, as to much will discolor the roller table and render the adhesion of the shellac useless.

Regards,
Bila