Measure the pencil and choose the socket together
Measure the end your topper will slide over. Include the painted coating or a metal eraser ferrule if that is the part you’re covering. Calipers make small differences easier to read than a ruler.
For a round pencil in a round socket, enter the outside diameter. A round socket can also fit a hexagonal pencil: measure that pencil corner to corner. If you choose a hexagonal socket, measure across the opposing flat faces instead. Using an across-flats measurement for a round socket can make the opening too small.
Understand what the clearance setting changes
The pencil width is your measurement. Clearance is the extra space on each side of that width. Bobble Studio calculates the socket width as:
Socket width = pencil width + (2 × clearance)
For example, a 7.0 mm measured width with 0.2 mm clearance makes a 7.4 mm opening. In a round socket this is the diameter; in a hexagonal socket it is the distance across the flats. These numbers illustrate the setting, rather than a recommended size for every pencil.
The printed opening can differ from the design. Filament, extrusion settings, the first layer and your printer’s calibration all affect the final fit. The fit samples let you check that on your own machine.
Print the little samples before the big head
- Prepare the kit with your measured width, chosen shape and socket depth.
- Open fit-test.3mf and keep it at 100% scale. The separate objects are named by their clearance; individual STL versions are also in the bundle.
- Use the same material and print profile you plan to use for the head.
- Let the samples cool. Remove any material obstructing the opening and gently try them on the pencil.
- Choose a secure fit that can be removed without cracking. Select that clearance in the studio and prepare the matching head again.
If every sample is tight or loose, recheck your measurement, change the clearance and print the samples again. Don’t force a tight PLA socket onto the pencil.
Change the head size without changing the fit
Scaling the entire exported model in a slicer also scales the hole. A 10% larger head would have a 10% wider socket, undoing the fit you just tested.
Instead, adjust Head height in the studio and prepare the head again with the same successful socket settings. The head changes size while the specified socket width and depth stay fixed. This reuses your saved 3D head; it does not buy or generate a new face.
Keep primer, paint and varnish out of the socket. Even a thin coating reduces the space. The print and paint guide covers supports, starting PLA settings and finishing.