The TBK 938S is a smart screen polisher that removes light scratches from glass with a rotating pad and polishing compound. It restores the finish of lightly worn screens, but it cannot repair deep cracks or damaged coatings. Digi4u supplies the TBK 938S for shops and refurbishers.
Last updated: August 2026 ¡¤ Reviewed by the Digi4u repair team.
About this guide: based on hands-on bench testing and repair experience; confirm official specifications with the supplier before ordering.
What the TBK 938S does
The machine holds a polishing pad against the screen with a controlled motion while the operator applies the appropriate compound. The abrasive action removes a microscopic layer of glass, which flattens light scratches until they are no longer visible.
The “smart” part of the machine is the controlled operation: consistent pad speed and pressure give a more even result than hand polishing, which is why the tool is used before a screen is re-sold or re-laminated.
What it can and cannot fix
| Screen condition | Polishing result |
|---|---|
| Light surface scratches | Usually removable |
| Scuffs from keys and coins | Often removable |
| Deep scratches | Partially improved, still visible |
| Cracked glass | Not a polishing job |
| Damaged oleophobic coating | Cannot be restored by polishing |
The honest expectation is that polishing improves light wear, not that it makes a damaged screen new. Deep scratches and cracks need a glass replacement or a full screen assembly.
The polishing workflow
- Clean the screen and tape any openings.
- Apply the correct compound for the scratch depth.
- Run the polisher in even passes across the affected area.
- Wipe the residue and check the result under light.
- Repeat with a finer compound if needed, and re-apply a protective film after.
Safety and limits
Polishing removes material, so over-polishing can thin the glass or damage the edge where the panel bends. Work in short passes and check the result regularly. The machine is also not designed for curved edges or foldable screens, which need different treatment.
Who should buy one
The TBK 938S suits refurbishers who resell phones and screens, where a lightly scratched display is a saleable unit after polishing. Repair shops that simply replace broken screens may find it useful as a second line, but it is not a replacement for screen replacement.
Polishing vs replacement: the decision
The polisher changes the economics of a used phone, but only when the screen is worth saving. The decision starts with the scratch test: run a fingernail across the scratch. If it catches, the scratch is deep enough that polishing will only reduce it, not remove it. If the nail slides over it, the scratch is surface-level and a polishing pass is likely to help.
The second check is the panel condition. A screen with dead pixels, a yellow tint or touch damage is not a polishing job, because the fault is under the glass. Polishing those screens wastes time and raises the false hope that a new-looking surface fixes a dead panel.
The honest benchmark is the resale price: polish the screen when the finished unit sells for more than the parts and labour. For a shop, that means testing the panel first and polishing only the screens that will sell. The machine pays for itself on the screens it saves, not on the ones it touches.
Apply the scratch test before the polish and the resale check before the decision. The screen polishing and refurbishing tools at Digi4u include the machine and the compounds, and the test keeps the polish where it earns.
Related guides: the screen grades guide explains how replacement screens are graded, and the tempered glass range covers the protective layer to fit after polishing.
Digi4u workshop notes
Our bench rule: polish the light scratches, replace the deep ones. The machine earns its place before a screen is re-sold, not before a cracked panel is fitted.
¡ª Digi4u repair team (bench notes)
Conclusion
The TBK 938S removes light scratches with controlled pad action, which makes worn screens saleable again without a replacement. See the screen polishing tools at Digi4u.
Frequently Asked Questions
Does the TBK 938S remove deep scratches?
No. It improves light surface wear. Deep scratches and cracks still need glass or screen replacement.
Is screen polishing safe?
Yes, when done in short passes with the correct compound. Over-polishing can thin the glass or damage edges.
What do I need after polishing?
Clean the residue and re-apply a protective film or tempered glass, because polishing can remove the original coating.
