3DPrintCalcs
Bearing Calculator — Seat & Shaft Dimensions
Calculate bearing seat dimensions and tolerances for standard bearings.
How We Calculate This
Bearing Seat Calculations
- Seat diameter (hole) = Bearing OD + Fit offset + Printer tolerance
- Shaft diameter (peg) = Bearing bore + Fit offset − Printer tolerance
- Seat depth = Bearing width + 0.2mm clearance
The seat is a hole and FDM holes print smaller than designed, so the printer tolerance is added to the modelled seat so it lands on size. The shaft is an external peg and FDM outer walls print larger than designed, so the tolerance is subtracted from the modelled shaft so it still passes through the bore. A negative fit offset makes the seat tighter (press fit, held by friction); a positive offset makes it looser (drop-in).
Frequently Asked Questions
The 608 bearing (8mm bore, 22mm OD) is the most common in 3D printing projects, often used for wheels, rollers, and spool holders. 625 bearings (5mm bore) are also popular for smaller mechanisms.
Press fit is preferred as it allows bearing replacement. Design the seat 0.05-0.1mm smaller than the bearing OD (accounting for printer tolerance). If the fit is too loose, a drop of CA glue or Loctite secures it permanently.
FDM holes typically print 0.1-0.3mm smaller than designed. This calculator adds your printer tolerance to the seat diameter to compensate. Test with a calibration print and adjust the tolerance value accordingly.
For low-speed, low-load applications, printed journal bearings (plain bearings) can work. Use Nylon or PETG for the bearing surface. For anything above 100 RPM or with significant load, use proper metal ball bearings.
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Last updated: February 2026
All calculations are estimates. Always verify settings with test prints before committing to final prints.