Round brass thimbles are the traditional grommet choice for inserting in a rope eye. Also used for jacklines.
The Name/size of the Thimble is equal to the middle opening across.
This List is the max size of the Cord/Rope Diameter to fit in the outer groove around the thimble:
1/4" Thimble = 3/16" cord/ groove
3/8" Thimble = 1/4" cord/ groove
5/8" Thimble = 3/8" cord/ groove
3/4" Thimble = 3/8" rope /groove
If I was making a Bell Rope let's say, and wanted to use these for the eye.. I most often go to my personal notes below:
I would use a -
1/4" Thimble for - a single strand of #120, #96, or #60. #45 would need to be hitched. or 3 #15b's or 3 #21s.
3/8" Thimble for - 3 #30's.. is great is hitched. 3 #45's only if they are twisted and Not hitched. or more of smaller cords.
5/8" thimble for - If I use ringbolt hitching around 3 strands of #120, or even twisted 3 120 together. or 4 strands of #60, or 8 strands of #30. you get the idea.
3/4" thimble for 4 or more #120 strands.
(please send me your notes if you find something different or better to share with everyone!)
These come from Sailrite.com. My price is a hair above theirs because I shipped them here, so y'all can buy them here with your cord vs buying them there and paying shipping as well. but I encourage you to go check out their page. As I'm slowly buying from them to offer here until I get wholesale with them.