Bearing Removal: Puller, Hydraulic, Induction

Bearing removal is the process of separating a rolling bearing from a shaft or housing without damaging the shaft, mounting seat, or the replacement bearing. This is a core maintenance skill — a single mistake can destroy a shaft worth tens of millions in replacement cost and ruin a new bearing before it's even installed.

There are three primary removal methods: mechanical pulling (bearing puller), high-pressure oil injection through an axial hole (oil injection), and induction heating to thermally expand the inner race. Which method you choose depends on the mounting fit (tight-fit or push-fit), shaft diameter, and available workspace. Using a hammer and chisel is incorrect practice — it creates impulse loads on the rolling paths and leaves permanent metal dents on the shaft.

Definition and Technical Requirements

A bearing installed with an interference fit (tight-fit) means the inner race is pressed onto the shaft with negative tolerance — typically k5, m5, or n6 according to ISO 286-1. A 6308 C3 bearing (d=40 mm) mounted with k5 shaft tolerance creates interference force ranging from 8 to 15 kN depending on temperature. To remove it, the pull force must overcome this without creating eccentric (off-center) loading.

The underlying physics is elastic deformation. When a bearing inner race is pressed onto a shaft, the contact pressure at the fit surface creates a friction coefficient typically between 0.12 and 0.18 for clean, dry surfaces. For a 6308 C3 with 12 kN nominal interference, the total holding force equals interference force multiplied by friction coefficient and the contact perimeter — easily 15–20 kN. Corrosion, thermal cycling, or oil oxidation can increase this effective friction, making the bearing seemingly welded to the shaft.

Technical requirements before removal:

• Identify the mounting type: consult the drawing or measure actual tolerance with a caliper — tolerance classes ISO p6, r6, or n6 indicate very tight fits requiring specialized equipment
• Note the load direction: the race under combined load typically mounts tighter than the unloaded race; on a horizontal shaft, the lower race usually experiences greater interference than the upper race
• Check for oil holes: many modern industrial shafts have high-pressure pump holes ready to use; drilling retrofit holes creates stress concentrations
• Clean the surface: rust and debris increase removal force by 20–40% versus theoretical prediction; surface contamination acts as mechanical locking
• Measure temperature: bearing removal is easier when conducted at elevated temperature (60–80°C); cold weather or air-conditioned shops increase required pull force by 10–15%

According to SKF Maintenance and Lubrication Guide, over 70% of bearing failures during reinstallation stem from removal mistakes: shaft scratching, race spalling, or bearing seat oxidation from prolonged exposure. The cost of a damaged shaft can exceed the replacement bearing cost by 10–20 times, making proper removal technique a critical cost center in industrial maintenance budgets.

Required Tools

Selecting the right tool determines 80% of your success. There is no universal tool — each has a specific application range. Investment in proper tools is standard practice at all major industrial maintenance centers, from automotive OEM workshops to power generation stations.

Bearing Puller (Mechanical Puller)

Two- or three-jaw mechanical pullers are the first choice for small to medium bearings (d ≤ 100 mm). The jaws must grip the inner race, never the outer race or housing when pulling across a shaft. SKF TMMP 50 and FAG PULLER 50 are the most common mechanical pullers available in Vietnam; both are rated to 50 kN pulling capacity.

Mechanical pullers convert rotational force (torque from a screw) into linear pulling force. The mechanical advantage depends on jaw spacing and screw pitch — most commercial pullers provide 5:1 to 10:1 leverage. A hand-tightened screw that rotates 5 turns with 1 mm pitch provides 50 mm of linear advancement; with 10:1 mechanical advantage, this equals 500 N of linear pull per 10 kg of hand force. For larger forces, a ratchet wrench or breaker bar becomes necessary.

Screw-type pullers work when pull force is under 30 kN. Above that threshold, use a hydraulic or integral pump puller to avoid sudden jam of the screw threads and to distribute force more evenly. Hydraulic-integral pullers have a small hand pump built into the puller frame, allowing controlled pressure buildup without external equipment.

Hydraulic Nut (Hydraulic Actuator)

Hydraulic nuts such as SKF HMV/HMVC or FAG HYDNUT mount on the tapered shaft end and build pressure to push the bearing out along the axis. Use this for bearings mounted on tapered bores (marked K30, K15 in the bearing code) or shafts with prepared threads. Working pressure typically 100–160 MPa.

These are most effective on large shaft diameters (d > 80 mm) where the bearing bore and shaft taper provide good load distribution. The hydraulic nut applies force axially, pushing the bearing out along the shaft without eccentric loading — ideal for machines with limited lateral workspace. Many industrial conveyors and gearbox assemblies are designed with tapered shaft ends specifically to enable hydraulic nut removal during scheduled maintenance.

Induction Heater (Induction Heating Equipment)

Induction heaters like SKF TIH or BEGA use high-frequency alternating magnetic fields to induce eddy currents in metal, raising bearing temperature to 80–110°C in 1–3 minutes without open flame. At 110°C, the bearing expands by approximately 0.08–0.12 mm per 100 mm diameter — enough to reduce pull force to nearly zero for many medium fits.

The thermal expansion effect is predictable and reversible. For ferrous metals, the coefficient of linear thermal expansion is approximately 12 × 10⁻⁶ /°C. A bearing with d = 100 mm heated from 20°C to 110°C expands by: 100 mm × (110–20)°C × 12 × 10⁻⁶ = 0.108 mm. For a bearing with k5 or m5 fit, this thermal expansion alone can reduce interference from 20 kN to near zero, making mechanical puller assistance barely necessary. Once the bearing cools back to ambient, the thermal fit disappears and normal assembly can proceed.

Removal by Mechanical Puller — Tight Fit

Standard bearing removal procedure (d ≤ 80 mm)

Step 1 — Preparation: Clean the shaft surface with solvent, verify there are no retaining keys, lock washers, or snap rings left behind. Many puller jaw failures trace back to overlooking this step. If a retaining ring is present, it must be removed completely — attempting to pull with a snap ring in place can shear the inner race or break a puller jaw.

Prepare a clean, flat work surface. Place wooden blocks underneath to support the shaft at its midpoint, preventing the shaft from bending under the pull force. The shaft should be horizontal and level; tilting creates eccentric loading.

Step 2 — Position puller jaws: Grip the inner race face evenly across all three jaws. For two-jaw pullers, position symmetrically 180° apart. Center the pull screw precisely on the shaft axis — off-center pull creates bending moment that scratches the shaft.

For three-jaw pullers, rotate the jaws so they contact the bearing at 120° intervals. This distributes radial load evenly and minimizes tilting. The jaw contact point should be on the flat face of the inner race, not on the rolling path or chamfered edge. If the bearing has a shoulder or snap ring groove, the jaw grip must be inboard of these features.

Step 3 — Apply pull gradually: Tighten the pull screw by hand, observing pull force through a torque wrench or feel. If the bearing does not shift after firm tightening, STOP — do not increase force by extending the screw with a lever arm without proper equipment. Listen for sounds of movement — a quiet creaking sound indicates the bearing is beginning to shift. If you hear cracking or loud pops, stop immediately and reassess jaw position.

Typical pull times range from 5 to 15 minutes for d ≤ 80 mm with firm hand torque. If the bearing has not begun moving after 10 minutes of continuous pressure, reduce the puller force, reposition the jaws, and try again. Forcing can break puller jaws or crack the bearing.

Step 4 — Gentle heat assistance (if needed): Use a heat gun (not a welding torch) to warm the inner race to 60–80°C while maintaining puller pressure. Stay below 120°C — beyond that threshold, bearing steel (GCr15, 100Cr6) begins to lose hardness. Heat gun exposure typically requires 2–5 minutes to bring the bearing from room temperature to 70°C, depending on bearing size and heat gun power.

Thermal assistance reduces the required pull force by 40–60% in many cases. The heat allows the shaft steel to expand slightly, reducing the contact pressure and friction. Apply heat to the inner race face or side, not to the rolling path. Once the bearing begins moving, you may maintain or reduce the pull speed.

Step 5 — Support immediately: When the bearing separates, catch it right away to prevent dropping. Inspect the shaft immediately — any longitudinal scratch must be polished smooth before installing the replacement bearing. Deep scratches or gouges should be assessed by the equipment manufacturer to determine if the shaft can be restored through polishing or must be replaced.

Blind bearing removal (puller without access)

When a bearing sits in a blind hole (sealed in a gearbox, crankshaft end, or bronze bushing housing), standard puller cannot reach it. Use a slide hammer with expanding collet: insert the collet inside the bearing, expand it to grip the inner race, then strike the slide hammer backward to pull.

Example: A 6205 bearing (d=25 mm) inside a hydraulic pump head typically sits fully in a blind cavity — a three-jaw puller has no access point. The Kukko 21-3 slide hammer set or SKF TMBP 50E handles this efficiently. See more about this bearing type at rolling ball bearing product page.

Removal by Hydraulic Pump — Oil Injection

Oil injection principle

High-pressure oil pumped into the interface between bearing and shaft — a method developed by SKF and documented in SKF Bearing Maintenance Handbook — allows removal of large bearings without significant pull force. Oil is introduced through the shaft center hole or pre-drilled port at the mounting face, creating a high-pressure oil film that nearly eliminates friction between shaft and bearing.

The physics: oil is incompressible and fills the microscopic surface roughness between shaft and inner race. Once pressurized, the oil creates a full fluid film, separating the metal surfaces. The bearing inner race no longer "grips" the shaft — instead, it floats on a pressurized oil layer. This reduces effective friction coefficient from 0.15–0.18 down to 0.05–0.08, making the required pull force drop by 60–80%.

Working pressure: 150–350 MPa depending on size. Hand pump SKF 226400 or electric pump TMJL 50 can reach 400 MPa. Pressure gauges on the pump allow precise monitoring — critical for preventing over-pressurization, which can break seal rings or burst weak points in the shaft.

Application conditions

The shaft must have an oil hole (drilled at center or port) and an oil groove (radial or axial slots at the mounting face). This is a design requirement — cannot be retrofitted to shafts lacking these features. Modern industrial shafts ≥ 100 mm diameter are typically pre-drilled per ISO 15243:2017.

Retrofitting oil holes requires drilling from the shaft end, threading a path through the shaft center, and creating distribution slots at the mounting face. This is time-consuming and adds cost; that's why new equipment is designed with oil holes from manufacture. On existing shafts without oil holes, cost of drilling and grooming often exceeds the cost of replacing the shaft itself.

Procedure

1. Install a loose lock nut at the shaft end to catch the bearing if it suddenly breaks free. The lock nut should have enough clearance that the bearing can slide freely beneath it as it's pushed out. Verify the threads match the shaft size.

2. Connect pump to the oil hole; verify all connections are sealed. Use thread sealant (PTFE tape or pipe dope) on connections to prevent oil spray. Attach a pressure gauge to monitor pressure buildup in real time.

3. Increase pressure gradually — 50 MPa per minute; watch bearing motion. Do not rush; rapid pressure spikes can damage internal components of the bearing or cause sudden, uncontrolled movement.

4. Once bearing begins moving (visible axial displacement), reduce pump rate; support bearing with the other hand. Many technicians use a wooden block or brass drift to catch and slow the bearing as it moves. This prevents sudden ejection and bearing damage.

5. Release pressure immediately after bearing clears the shaft; do not leave residual pressure. High residual pressure can damage seals if left unattended. Open the bleed valve on the pump or slowly loosen the connection fitting to allow pressure to drop safely.

This method suits bearings 22220 EK/C3 (d=100 mm, D=180 mm, B=46 mm, C=365 kN) and larger — sizes where mechanical pullers lack capacity and induction heating takes longer. Oil injection is the standard method in automotive assembly and heavy equipment maintenance. See more on tapered bore bearings at product page.

Removal by Induction Heating

Advantages over open flame

Induction heating delivers precise temperature control — critical because bearing steel (GCr15, 100Cr6) loses hardness if sustained above 150°C. Oxy-acetylene torches create localized hot spots of 800–1200°C — destroying surface finish and warping the shaft. Electromagnetic induction at 1–10 kHz distributes heat evenly across the entire bearing.

Procedure for removing inner race with induction heater

Step 1 — Thermal insulation: Use the insulation sheet (usually supplied with the heater) placed between bearing and shaft to prevent the shaft from absorbing heat.

Step 2 — Attach magnetic yoke: Select a yoke matched to bearing diameter. Position it flush against the inner race — avoid contact with rolling paths or rolling elements.

Step 3 — Heat: Switch on the heater; set target temperature 100–110°C. Modern units have thermal sensors and auto-shutoff. Duration: 60–180 seconds depending on diameter.

Step 4 — Pull immediately: Once temperature target is reached, apply gentle pull with a light puller — required force drops 60–80% versus cold pull. If the bearing has not freed after 30 seconds heating, raise temperature 10°C and retry.

Step 5 — Demagnetize: After removal, run the demagnetize program on the heater. A magnetized bearing will attract steel particles from the lubrication oil, sharply reducing service life per FAG/Schaeffler Industrial Bearing Solutions Guide, 2023.

Application: stuck inner race after outer removal

Common scenario: outer race and rolling elements have been removed (due to failure or partial disassembly), but the inner race remains stuck on the shaft. The puller has no grip point. Induction heater is the only non-destructive solution: position yoke around the inner race, heat it, the race expands and can be pulled by hand or light puller.

Common Mistakes

Most shaft and bearing housing failures in shops result not from poor-quality bearings — but from incorrect removal technique.

1. Using hammer and chisel

This is the most serious and most common mistake. Each hammer blow creates impulse load of tens of kilonewtons over microseconds — this impulse travels through rolling paths and leaves permanent dents (brinelling) on inner race, outer race, or both. Per ISO 15243:2017, false brinelling and true brinelling rank among the four most common damage modes, and both can originate from improper removal.

If a puller is unavailable, lay the shaft horizontally on a flat surface and use proper support — never strike the bearing directly.

2. Pulling through the outer race during shaft removal

Pull force must act on the component under interference. When removing a bearing from a shaft, interference load is on the inner race — the puller jaw must grip the inner race. Pulling through the outer race transmits full force through the rolling elements and paths, causing instant brinelling.

3. Off-center pull

Uneven puller jaws, offset pull screw, or a bearing that begins tilting without correction — all create bending moment on the shaft, potentially kinking small shafts or scratching the mounting surface.

4. Leaving shaft bare after removal

The shaft surface must be protected immediately after bearing removal — wipe clean, apply a thin corrosion-preventive grease, and wrap. Thirty minutes of exposure to a workshop environment is enough to initiate surface oxidation. Even minor rust spots increase the pull force for the replacement bearing, violating tolerance fit.

5. Using a welding torch instead of induction heater

Uncontrolled heat from an oxy-acetylene torch destroys the shaft surface finish (hardness drops from HRC 58–62 to HRC 30–40 in seconds). A softer shaft will deform under load, and the replacement bearing will be loose immediately after startup.

Real-World Case

At a seafood processing plant in Can Tho, the maintenance team needed to replace a series of 22220 EK/C3 tapered bore bearings (d=100, D=180, B=46, C=365 kN) on the frozen product conveyor — 12 positions total, scheduled maintenance every 8,000 hours.

Previously, technicians used a 150 kN hydraulic puller combined with heating from an oxy-acetylene torch. Each bearing removal took 45–60 minutes, and 3 of the 12 shafts showed visible scratches afterward.

After switching to a three-tool method — SKF TIH 030M induction heater, hydraulic puller, and HMV 20 E hydraulic nut — removal time per bearing fell to 18–22 minutes. More importantly, no shaft damage was observed across three subsequent maintenance cycles (totaling ~24,000 accumulated running hours). The equipment cost recovered on the second maintenance cycle through reduced downtime.

Lesson: investing in proper tools is not an expense — it is insurance for your shafts and replacement bearings.