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How to Use a Hydraulic Press for Assembly
Guide · Updated October 28, 2026
A hydraulic shop press pushes bearings, bushings and pins in or out with controlled force. Good fixturing and pressing on the correct part of the bearing matter more than tonnage.
Check the fit first
Measure the shaft and bore before pressing. The free Gage Block Calculator builds the stack.
Step by step
- Measure the parts: Confirm the interference is what the drawing calls for.
- Support the work: Support on the part being pressed into, not on a race that will carry the force through the balls.
- Push the right race: Press on the inner race for a shaft fit, the outer race for a housing fit.
- Align: Start square; use a pilot or chamfer.
- Lubricate: Light oil or assembly lube on the surfaces.
- Press steadily: Watch the gauge; a sudden jump means binding.
- Check: Check the part spins freely and is fully seated.
Worked example: force from the gauge
A press with a 2.000 in diameter piston: area = π × 1.000² = 3.1416 in². At 3000 psi gauge pressure, force = 3000 × 3.1416 = 9425 lb, about 4.7 short tons. Use this to compare the force against expected; if a small bushing takes far more than usual, stop and check the fit.
Safety
Wear eye protection. Keep hands out. Parts can shatter under load; use a guard.
Heat or cold instead
For heavy interference, heat the housing or bearing or cool the shaft rather than forcing.
Common problems
Galling: no lube or too much interference. Cocking: not square. Brinelled bearing: pressed through the balls.
Tips
- Interference: turn a journal to size.
- Bore: dial bore gage.
- Mic: check a micrometer.
Quick shop check
Press force for a bearing fit can be estimated by experience, but always stay below the press rating. A 1/2-inch bore steel bushing with 0.0010 in interference may need only a few tons; if pressure rises sharply and the part stops, stop and check alignment rather than adding force. Press only on the ring being fitted; pressing through the balls brinells the race.
FAQ
Which race do I press?
The one being fitted: inner for shaft, outer for housing.
How do I find force?
Pressure × piston area.
Should I lubricate?
Yes, lightly.
When to use heat?
Large interference fits.
Why did my bearing get noisy?
Pressed through the balls.
Related guides and calculators
- How to Turn a Journal on a Lathe
- How to Use a Dial Bore Gage
- How to Check a Micrometer with Gage Blocks
- How to Use a Keyway Broach
- How to Deburr and Break Edges
- How to Cut Internal Square Threads on a Lathe
- How to Level a Lathe Bed
- How to Use an Arbor Press
- How to Calculate Press Fit Pressure and Pressing Force
- All free machinist calculators
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General shop information only — follow your machine and tooling manufacturer's instructions and your shop's safety rules.