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How to Align a Lathe Tailstock
Guide · Updated October 28, 2026
If the tailstock center is off the spindle axis, work held between centers or supported by the tailstock turns with a taper. Aligning it takes an indicator and a test bar or a two-collar test cut.
Measure the taper
Measure both collars with a mic you've checked against gage blocks; the free Gage Block Calculator builds the stack.
Step by step
- Clean the tapers: Clean the spindle and tailstock tapers and the centers.
- Mount a test bar: Hold a ground test bar between centers, or turn a test piece supported by the tailstock.
- Indicate the side: Run an indicator on the carriage along the side of the bar from headstock to tailstock.
- Read the change: Note the change in reading over the length; that is the horizontal error.
- Adjust setover: Loosen the tailstock clamp and move the setover screws by half the diameter error.
- Recheck: Lock the clamp and indicate again, since locking can shift it.
- Test cut: Take a light cut on two collars and compare their diameters.
Worked example
Two-collar test, 6 in apart: the tailstock collar measures 1.0010 in and the headstock collar 1.0000 in. Diameter error is 0.0010 in, so move the tailstock 0.0005 in toward the operator (the large end needs to come closer to the tool).
Height error
Tailstock height can be off from wear. Check with an indicator over the top of the test bar; height errors are usually fixed by shimming or scraping, not the setover screws.
Headstock vs tailstock
If a test cut with no tailstock still tapers, the headstock or bed is out. Fix that first, then align the tailstock.
Tips
- Use a dial indicator on a mag base on the carriage.
- Check runout first: runout and TIR.
- Remember setover is half the diameter difference.
- Recheck after moving the quill out a long way.
FAQ
How do I know if my tailstock is out?
Work supported by the tailstock turns with a taper, or a test bar indicates differently at each end.
How much do I move the tailstock?
Half the difference in diameter between the two ends.
Can I fix tailstock height with the setover screws?
No, setover only moves it sideways; height needs shims or scraping.
What is the two-collar test?
Turning two collars far apart and comparing diameters to find taper.
Should I check the headstock first?
Yes, make sure the headstock turns straight without the tailstock first.
Related guides and calculators
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- Magnetic Base Indicator Setup
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- How to Measure a Taper
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- How to Cut a Taper on a Lathe
- How to Turn Between Centers With a Lathe Dog
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