An uneven contact pattern across a machine-tool guideway is evidence about load transfer, geometry and lubrication, not a thickness specification by itself. If one end marks heavily while the other end is almost clear, record the condition before ordering a new PTFE slideway liner. This keeps the repair decision tied to measured geometry instead of a visual impression.
What an uneven pattern tells you
A contact check that marks one end heavily and leaves the other end almost clear means the slide is not transferring load uniformly. The cause may be taper, a hollow or crowned way, a distorted gib, incorrect assembly or a lubrication path that changes friction during the test. The pattern is useful evidence, but it is not proof that the liner alone is worn out.
Record the pattern before changing anything
- Clean the mating faces and remove loose oil, chips and old marking residue without altering the reference surfaces.
- Mark the travel direction and divide the contact length into repeatable stations from one end to the other.
- Apply a thin, consistent film of Tuschierpaste to the reference face and bring the members together without forcing a tight gib.
- Separate the members in the same direction each time, photograph the marks and note heavy, light and missing contact zones.
- Repeat after the slide is moved to another travel position so a single local mark is not mistaken for full-length bearing.
Separate contact, geometry and lubrication causes
| Observed pattern | Likely investigation direction | Evidence to collect |
|---|---|---|
| Heavy at one end, light at the other | Taper, misalignment or uneven gib pressure | Straightedge or indicator readings and gib condition |
| Narrow bands with gaps | Local high spots, scoring or debris | Surface inspection and repeat contact map |
| Pattern changes after oiling | Interrupted supply or contaminated oil film | Groove continuity, metering and wiper checks |
| Uniform marks but rough low-speed travel | Friction, servo or adjustment issue | Slow traverse, reversal and lubrication observations |
Do not size the liner from the darkest mark
The darkest contact spot shows where the members touch under the test condition; it does not define the finished liner thickness or the load capacity of the repaired way. Measure the removed material, original centre height, bearing footprint and available machining allowance. Then review the slideway liner sheets and strips guide before selecting a size and the Blue TEBAK slideway liner page before requesting a sample.
Prepare a measured repair brief
- Machine and axis identification, travel length and load direction.
- Contact photographs or a station-by-station map showing heavy and missing marks.
- Measured taper, flatness, parallelism, centre height and gib condition.
- Oil type, groove layout, wiper condition and whether the pattern changes after lubrication.
- Required liner color, width, finished thickness, machining allowance and total length.
TEBAK supplies PTFE-based slideway liner in Blue, Green, Brown and Brick Red. Color is a workshop identifier; the repair decision still depends on measured geometry, the load path and a clean, prepared bond surface. For the bonding specification, see the TEBAK Two-Part Epoxy-Adhesive.
Acceptance checks after relining
After the liner cures and is finish-machined, repeat the same contact stations and compare the pattern with the pre-repair record. Check full-travel handwheel effort, centre height, parallelism, gib adjustment and oil coverage. The objective is not a visually dark mark everywhere; it is stable, appropriate bearing contact with smooth motion and the intended geometry.
Need a measured liner recommendation?
Send the contact map, way dimensions, required color, thickness, width and total length. TEBAK can review the repair brief before you approve a replacement liner order.
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