Installation Guide
Slideway Liner Bonding Mistakes to Avoid
A slideway liner that lifts within a season is usually not a material fault. This guide sets out the five bonding mistakes that account for most early failures, the signature each one leaves on the joint, and the checks that catch them before the machine goes back together.
Direct answer: five mistakes cause most early liner failures
Liner that lifts, blisters or creeps loose within a season is rarely a material problem. The same five errors recur in relining work: bonding the untreated face, clamping hard enough to starve the glue line, mixing adhesive by eye, bonding a strip that still carries roll memory, and bonding onto cast iron that is still bleeding oil. Each one leaves a different signature on the joint, and the signature is what turns a failure into a diagnosis instead of an argument.
Mistake one: bonding the untreated face
PTFE is chemically inert, so the face that will be bonded is etched or otherwise treated by the maker, and the two faces of a strip are not interchangeable. Bonded the wrong way round, the adhesive has nothing to key to: the strip comes away cleanly with the adhesive left sitting on the iron, often within days of machining. Nothing recovers that strip, because the treatment cannot be recreated in a workshop. Mark the treated face as soon as the roll is opened, keep the marking visible through cutting and trial fitting, and where the marking is lost, confirm the face with the supplier instead of judging by sheen or colour.
Mistake two: clamping hard enough to starve the glue line
Clamping holds the strip in contact while the adhesive cures; it is not a way to squeeze adhesive out of the joint. Excess pressure drives resin from the bond line and leaves starved areas where strength is limited to the residue, while too little pressure leaves voids and a thick, weak line. Both look identical from the outside until the strip is loaded. Spread the load with a caul plate or flat bar, space clamps evenly along the strip, and judge pressure by a continuous bead of squeeze-out along both edges rather than by how tight the clamp feels.
Mistake three: mixing epoxy by eye and working past pot life
Two-part adhesive is unforgiving about ratio. Mixing by eye, or judging the hardener by colour, produces soft spots that only show up when the strip is machined or loaded; mixing a large batch to save time produces adhesive that has already begun to set before it reaches the surface. Work in batches sized to the strip, follow the ratio by weight where the datasheet gives one, and discard the batch once it starts to string or thicken. Pot life moves with shop temperature, so a mix that behaved in winter will gel in a summer workshop. A tap test along the cured strip, listening for a change in tone, finds soft areas before reassembly.
Mistake four: bonding a strip that still carries roll memory
Liner travels coiled, and a strip taken straight off a tight core is curved. Clamping a curved strip flat does not remove the set, it stores it, and the edges lift once the clamps come off. Unroll and lay the strip out at workshop temperature until it lies flat under its own weight, and check along the length rather than at one point. For long strips, ask for a core diameter that keeps the bend gentle and for flat packing where the route allows.
Mistake five: bonding onto cast iron that is still bleeding oil
Machine tool castings are porous, and years of way oil soak into the surface. Grinding or blasting opens the pores and the oil migrates back out under the adhesive, so the bond fails from the middle outward. Degrease, remove the contaminated skin mechanically, degrease again, and confirm with a water-break test: water should stand as an unbroken film. On castings that have been heavily oiled or previously repaired, a controlled warm dry-out before bonding is more dependable than another solvent wipe. This is the failure most often blamed on the adhesive and least often caused by it.
Reading the failure before choosing the repair
| What you see | Most likely mistake | Confirm by | What to change |
|---|---|---|---|
| Whole strip peels away, adhesive stays on the iron | Untreated face was bonded | Marking, or supplier confirmation of the treated side | New strip; the treatment cannot be restored |
| Blisters or dry patches under the strip | Starved glue line from over-clamping | Blade check at the edge, tap test along the strip | Caul plate, even clamp spacing, squeeze-out bead at both edges |
| Soft spots that appear during machining | Wrong mix ratio or adhesive used past pot life | Tap test along the cured strip | Ratio by weight, smaller batches, discard gelled mix |
| Edges lift after the clamps come off | Roll memory bonded into the strip | Lay the next strip out flat before bonding | Relax time, larger core, flat packing |
| Bond fails from the middle outward | Porous iron bleeding oil into the joint | Water-break test after surface preparation | Mechanical removal, warm dry-out, re-test before bonding |
Checking the bond before the machine is reassembled
A bonded offcut loaded to failure says more about preparation than any visual inspection. The friction pull test guide sets out how to measure breakaway force on a test piece and what a clean peel looks like next to a contaminated one, and the old liner removal guide covers getting the way surface back to something worth bonding to. Running both on scrap material before the production strip goes down is the cheapest insurance in the job.
Frequently asked questions
Can a lifted strip be re-bonded?
Not reliably. Once the treated face has been contaminated by handling or by the failed adhesive, the joint cannot be brought back to its original strength, and a re-bond usually fails again in the same place. Replace the strip.
How long should the clamps stay on?
Until the adhesive has reached the handling strength stated on its datasheet at the shop temperature in use, not until it feels set. Cold workshops extend that time considerably, so the datasheet curve is the reference.
Is a thicker glue line stronger?
No. A thick line is weaker in shear and creeps more. The target is a thin, continuous film with squeeze-out at the edges and no voids.
Does colour tell you which side is treated?
Not reliably. Colour identifies the grade family, not the bonding face. Use the maker marking, and ask the supplier when it has been lost.
Ordering the strip for the repair
TEBAK supplies the liner in the grades used on rebuild work: Blue, Green, Brown and Brick Red, together with two-part epoxy adhesive and Tuschierpaste for the contact check after machining. Put grade, thickness, width and cut length on one line, and the strip can be confirmed against a single document.