Loctite Henkel Premium Partner
Free delivery from 600 EURO to EU Countries* 
+48 509 336 666
How much load can LOCTITE 638 bearing retaining compound handle? Watch our test!
In this post, we explain the principle of operation and show a practical strength test of a coaxial joint (ring–shaft) made with the anaerobic retaining compound LOCTITE 638. We measure the force required to press the joint apart on a press. It’s one of the clearest ways to show the potential of anaerobic retaining solutions—provided the process and surface preparation are done correctly.
Key takeaways
✅ LOCTITE 638 is an anaerobic retaining compound for coaxial parts (e.g., bearings, sleeves, rings)
✅ It cures after air (oxygen) is excluded between metal surfaces
✅ The test result applies to this specific sample and conditions—real performance depends on gap/fit, surface prep, temperature and curing time
LOCTITE 638 – what it is used for and how it works
LOCTITE 638 is an anaerobic retaining compound designed for bonding coaxial assemblies. It cures when oxygen is excluded in the joint—between close-fitting metal surfaces. It fills micro-irregularities, stabilizes the assembly and helps reduce micro-movement and loosening in service.
In practice, this type of solution is used for bearing retention, sleeves and rings—especially when repeatable assembly and joint stability matter.
Strength test: coaxial retention (press-out test)
According to the manufacturer, LOCTITE 638 is intended for high loads in coaxial joints. However, joint strength always depends on operating conditions and on joint geometry and surface preparation.
Video: How much load can LOCTITE 638 handle? Watch our test!
The video below shows a test where we measure the force required to separate the parts by pressing the joint out on a press:
How the test was performed
The test used a metal ring and shaft with a loose fit. The joint was assembled using LOCTITE 638. Then, on a press, the parts were pushed apart and the force was observed on the press gauge.
Result of this sample: in this specific configuration, it took nearly 900 kg of load to destroy the joint (separate the parts). This is an excellent result, but it is not a universal value for every application—real performance depends on gap/fit, overlap length, surface preparation, curing time and operating temperature.
The diagram below shows the press force calculation:
Extra videos: selection and correct use of anaerobic retaining compounds
If you want to translate this test into real maintenance/production practice (selection, surface prep, typical mistakes), these videos will help:
Anaerobic adhesives for bearing retention and other coaxial parts. Why are they worth using?
LOCTITE 603 – how to retain a bearing correctly with an anaerobic compound? How to use it for retention?
LOCTITE 660 – how to use a compound for retaining bearings and coaxial parts?
This is especially useful when there is wear/clearance (worn housing or shaft) and you want to strengthen the coaxial joint—always within the manufacturer’s recommendations and realistic tolerances.
What most affects retention strength?
- Gap / fit – loose vs tight fits behave differently.
- Contact area (overlap length) – typically, more area means higher capacity.
- Surface preparation – degreasing and cleanliness are critical.
- Material activity – affects cure speed and process repeatability.
- Operating temperature – higher temperatures can reduce strength; follow the manufacturer’s data.
- Curing time – full strength is achieved over time, not instantly.
When to use 638 vs 603 vs 660? Quick guide
- LOCTITE 638 – when you need high strength and stable retention in typical industrial conditions (bearings, sleeves, rings). This is the product tested here.
- LOCTITE 603 – when you want a clear, repeatable “step-by-step” approach for standard retention work and process implementation.
- LOCTITE 660 – when the issue is wear/clearance (worn housing or shaft) and you want to reinforce the joint without immediate mechanical repair—within manufacturer limits.
Tip: in most cases the outcome is driven by degreasing, gap/fit, curing time and operating temperature.
Mini assembly checklist (repeatability)
- Remove contamination and degrease both surfaces.
- Make sure the gap/fit is suitable for the application.
- Apply the compound evenly (avoid flooding the joint).
- Assemble parts and hold position.
- Allow time for handling strength and full cure (per TDS).
FAQ – bearing retaining compounds
Is “nearly 900 kg” the standard strength of LOCTITE 638?
No. It’s the result of this specific test setup (geometry, fit, prep and conditions). Real values can differ significantly.
Why does a retained joint sometimes fail even with a retaining compound?
Most often: insufficient degreasing, unsuitable gap/fit, too short curing time, or operating temperature outside the intended range.
Can a retaining compound replace a press fit?
In many applications, retaining compounds can significantly improve stability and repeatability, but selection should always match the design and service conditions.
Test summary
This test shows that LOCTITE 638 can withstand very high loads in coaxial retention—provided the process is prepared correctly and matched to the application.
About the author:
Marcin Filipczyk – long-time specialist in industrial bonding technology.
He supports manufacturing plants in implementing repeatable bonding processes: from selection and surface prep, through application and quality control, to testing and validation.
