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How to Turn a Journal on a Lathe
Guide · Updated October 28, 2026
A journal is the part of a shaft that runs in a bearing or bushing. It needs to be round, straight, concentric with the rest of the shaft and sized for the fit the bearing calls for. Turning between centers, a sharp finishing tool and careful measuring are the keys.
Size the journal to tenths
Fits are measured in tenths. Prove your mic on gage blocks at the journal size. The free Gage Block Calculator builds the stack.
Step by step
- Hold for concentricity: Turn between centers with a dog, or in a collet, so all diameters share one axis.
- Check the tailstock: Turn a test cut and measure both ends; align the tailstock if there is taper.
- Rough: Rough to about 0.010–0.020 in over size.
- Semi-finish: Take a pass to leave 0.002–0.003 in.
- Finish: Sharp tool with a nose radius, fine feed, same depth of cut along the journal.
- Measure at several points: Both ends and the middle, two directions each.
- Polish if needed: Light polish with fine abrasive only to improve finish, not to size.
Worked example
A 1.000 in journal for a bushing calls for a running fit with the shaft 0.0010–0.0020 in smaller than the 1.0000 in bore: target 0.9980–0.9990 in, aim 0.9985 in. After semi-finishing at 1.0012 in, the finish pass must remove 1.0012 − 0.9985 = 0.0027 in on diameter, or 0.00135 in on radius. Readings after the pass: 0.9986 in at the tailstock end and 0.9984 in at the headstock end, a 0.0002 in taper over 2 in; acceptable here, but shift the tailstock 0.0001 in for the next part.
Finish matters for bearings
A rough journal wears a bushing quickly. Aim for about 16–32 µin Ra for plain bearings; use a nose radius of 1/32 in or more and a feed well below the radius.
Common problems
Taper: tailstock offset. Out of round: worn centers or headstock bearings. Chatter: dull tool or too much overhang. Size drift: heat from cutting; let the part cool before final size.
Tips
- Centers: dead center for best concentricity.
- Tailstock: align the tailstock.
- Finish: surface finish basics.
FAQ
What is a journal?
The part of a shaft that runs in a bearing or bushing.
Should I turn between centers?
Yes when concentricity with other diameters matters.
How much do I leave for finishing?
About 0.002–0.003 in on diameter.
What finish for a bushing?
About 16–32 µin Ra.
Why is my journal tapered?
The tailstock is offset.
Related guides and calculators
- How to Use a Dead Center
- How to Align a Lathe Tailstock
- Surface Finish Basics
- How to Turn Between Centers With a Lathe Dog
- Turning Speeds and Feeds
- How to Cut Multiple-Start Threads on a Lathe
- How to Use a Radius Turning Attachment
- How to Use a Hydraulic Press for Assembly
- All free machinist calculators
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