Measure Baitcaster Crankshaft Yourself

FAQ: Which shaft bore (7×4 mm / 8×5 mm) do I need for my baitcaster reel handle?

Your reel is not on the compatibility list? No worries – just quickly measure the shaft yourself. The crucial factor is the shape/size of the crankshaft (shaft) onto which the handle is mounted. The common sizes are 7×4 mm and 8×5 mm.

Tip: Image shows the difference between 7×4 mm and 8×5 mm.

What you need

• Caliper (digital or analog). In a pinch, a ruler will do – but a caliper is much more accurate.
• Optional: a cloth to prevent small parts from rolling away (ball bearings love adventures).

How to measure correctly (in 60 seconds)

1. Remove the handle: Remove the cap, loosen the locknut/screw, and pull off the handle.
2. Important: Do not measure the nut/locknut, but the crankshaft (shaft) onto which the handle is mounted.
3. Measure width (first number): Place the caliper at the widest point of the shaft (usually “flat to flat”) and read the value. This is usually 7 mm or 8 mm.
4. Measure height/second side (second number): Rotate the caliper 90° and measure the narrower side. This is usually 4 mm or 5 mm.
5. Assign result:
   ≈ 7 mm & ≈ 4 mm → you need 7×4 mm
   ≈ 8 mm & ≈ 5 mm → you need 8×5 mm

Quick check if you’re unsure

• Measure 2–3 times (it’s easy to measure “crooked” once – happens to everyone).
• Values very close? Small deviations (e.g., 7.0–7.2) can be normal depending on the measuring point.
• If it’s not clearly 7×4 or 8×5: take a photo of the shaft + caliper display and contact us.

Quick reminder: You measure the shaft, not the nut – and you need two values at the end: width × height = 7×4 mm or 8×5 mm.