Oil-Free L-Gibs
We provide custom manufacturing of finished bronze parts and self-lubricating bronze, precisely based on our clients’ drawings.
Self-Lubricating Oil-Free L-Gibs for Machine Tool Slideways
Oil-Free L-Gibs are the adjustable strip that sets the running clearance between two sliding machine elements — a saddle on a bed, a knee on a column, a ram in its guides. This page covers bronze gib strips and linear guide wear strips: the forms they come in, why solid-lubricated bronze removes stick-slip, and how a replacement is measured, machined and fitted.
What a Machine Tool Gib Is
A machine tool slide has to be tight enough to hold position and loose enough to move. Those two requirements are set against each other by one part: the gib. It is a strip of bearing material held between the moving member and the way it slides on, and moving it slightly — along a taper, or against a set screw — changes the running clearance.
One face of the gib is fixed to the moving member, usually by countersunk screws; the other slides against the machine way. Because the gib is the cheaper and more accessible surface, it is the part designed to wear — adjusted first, replaced eventually, while the cast iron way survives.
Sets Clearance
Eliminates unwanted play between the sliding members, maintaining the required running clearance.
Carries the Load
Transfers cutting and operating forces from the saddle or ram into the machine way across the contact surface.
Ensures Smooth Sliding
Provides a controlled bearing surface that enables smooth, low-friction movement and helps prevent stick-slip.
Protects the Machine Way
Acts as the sacrificial wear component. It can be adjusted to compensate for wear and replaced when adjustment is no longer sufficient.
Common Names
Depending on the machine builder and region, this component may be called a gib strip, saddle gib, taper gib, keep strip, or L-gib when it incorporates a locating lip. Although the names vary, the basic function remains the same.
For replacement or custom manufacturing, provide a photo, drawing, and key dimensions to help identify the correct gib type and specification.
Gib Forms and How Each Is Adjusted
The form is set by the way geometry — a dovetail needs an angled gib, a flat way a parallel one — and by how the machine is adjusted in service. The table sets out the common sections.
| Form | Section | Adjusted by | Typical place | Notes |
|---|---|---|---|---|
| Flat gib | Parallel strip, constant thickness | Set screws against the back, or shims | Flat ways, straight dovetails | Simplest to make. Wear take-up is stepwise rather than continuous. |
| Taper gib | Thickness tapers along the length | Axial pull from an adjusting screw, locked by a second screw | Lathe cross-slides, mill knees, dovetail ways | The most common form. Continuous take-up; the wedge is largely self-locking. |
| Dovetail gib | One face angled to match the dovetail | Screw or wedge at the narrow end | Column and knee dovetails | Carries side load as well as setting clearance. |
| L-section gib | Strip with a lip or return along one edge | Screws through the web | Retrofits, repair work, enclosed slots | The lip locates the strip and stops it walking out of the slot. |
| Flanged gib | L or T section with a mounting flange | Bolted through the flange; shimmed | Press rams, planer tables, large boring mills | Used where the gib also has to be positively retained. |
| Round gib | Cylindrical or half-round bar | Clamped in a matched groove | Round ways, some grinder tables | Rotates slightly in service, which spreads wear around its circumference. |
| Gib liner | Thin flat strip bonded to the existing gib | Not adjustable itself — it restores the parent gib | Rebuilding a worn gib in situ | A repair route where the original gib is sound but worn thin. |
Why Slideways Stick, and What Solid Lubricant Changes
A machine tool slide runs slowly under high load and reverses constantly. That is precisely the condition in which an oil film cannot build: there is not enough surface speed to drag lubricant into the contact, and every reversal squeezes out what little is there. The result is boundary lubrication.
Under boundary conditions the static coefficient of friction sits meaningfully above the dynamic one. So the slide does not start when the feed screw pushes — it stays put, the drive winds up, and then it releases in a jump. That is stick-slip: on a lathe or grinder, poor finish and an inability to hold a fine feed; on a mill, chatter marks and a table that will not feed smoothly.
Solid lubricant changes the ratio rather than the absolute value. Graphite plugs transfer a film to the counterface in the first hours of running, after which friction is far less dependent on velocity. The gap between static and dynamic friction narrows, and the slide creeps smoothly.
Solid lubricant does not replace a way-lubrication system that works — it covers the cases where oil cannot: vertical ways that drain, very slow feeds, long dwell times. The bronze helps too: it is conformable enough to spread load along the way rather than concentrating it, which is what wears a slide tight at one end of its travel.
Material Options
Material choice turns on whether the machine has working way lubrication, how heavily the slide is loaded, and what the counterface is. The table sets out the options we supply most often.
| Material | Lubrication | Load | Where it is used | Notes |
|---|---|---|---|---|
| Graphite-plugged tin bronze C93200 / CuSn8 base |
None — runs dry | Moderate to high | Lathe and mill dovetails, grinder tables, retrofit work | The default choice where maintenance-free operation is wanted. |
| Graphite-plugged aluminum bronze C95400 / C95500 |
None — runs dry | High | Press rams, planers, heavily loaded vertical slides | Carries more load than tin bronze but wants a hard counterface. |
| Leaded tin bronze C93200 |
Way oil or grease | High | Machines with a working way-lube system | Tolerant of grit and of a soft cast iron way; lower cost than plugged material. |
| Phosphor bronze C52100 / CuSn8 |
Way oil or grease | Moderate to high | Thin strips, spring elements, wrapped sections | High fatigue strength; used where the gib also has to flex. |
| Manganese bronze C86300 |
Grease, or plugged | Very high | Forging and press equipment, heavy planers | Used in heavy section; absorbs shock better than the tin bronzes. |
| Steel-backed bronze | Dry or oil | Moderate | Where the available depth is small | Bimetal construction; see composite bushings. |
Sizing, Fit and Adjustment
Three dimensions govern: length, which sets how much of the way is supported; width, fixed by the slot; and thickness, the dimension being adjusted. Machine tool gibs typically run 3–12 mm thick, with heavier sections on press and planer work.
Thickness and take-up
A gib should start with adjustment remaining in both directions. A replacement made to the same thickness as the worn part will be tight from the start, with no room to take up future wear. We normally supply slightly thicker than the sample and let the fitter bring it down at fitting.
Length
Longer is better, up to the limit of the slot. A short gib concentrates load into a small area of the way, and high local pressure over a short length produces the classic failure: a slide that is tight at one end of travel and slack at the other.
Clearance and preload
On a precision machine the target is a clearance small enough that a dial indicator barely moves when the slide is pushed by hand — typically 0.01–0.03 mm — with no tight spot anywhere in the travel. A small preload improves stiffness and damping; too much generates heat and makes the handwheel stiff.
The counterface
The way should be smoother than about Ra 0.8 µm and free of score marks. Against soft grey cast iron, a conformable leaded tin bronze runs better than a hard aluminum bronze, which polishes unevenly and can pick up. Where the slide is steel-on-bronze, hardening the way is worth doing at the same time. Measuring thin strip accurately needs care — see reading and measuring of bearing tolerance.
Machining, Drilling and Fitting a Replacement
Bronze machines easily, but thin strip and plugged stock each have one trap. The sequence below is the one we follow in our own shop.
- Measure the originalLength, width, thickness at both ends, taper, and hole positions from a common datum. On a taper gib measure thickness at three points so the taper is confirmed rather than assumed.
- Cut and drill on backingClamp the strip to a sacrificial backing plate — held directly in a vice jaw it will bow and spring out of flat. Drill with a sharp bit at reduced rake: bronze grabs on breakthrough. Peck and clear the flutes.
- Countersink and deburrCountersink so screw heads sit below the sliding surface, and stone off raised metal at the edges. A burr on the sliding face scores the way on the first stroke.
- Fit to the wayUse marking compound to check contact along the length and width, then scrape the high spots until contact is even. On a plugged strip, work the back face.
- Set the clearanceRun the slide through full travel and measure play with a dial indicator at both ends. Adjust, lock the screw, then re-check — locking usually moves the setting.
- Run in, then re-checkOn a graphite gib run the slide through several full strokes at low feed so the film forms, without cleaning the face with solvent. Re-check clearance after the first warm-up.
Gibs, Wear Plates and Rolling Linear Guides
Three solutions exist for the same problem, and picking the wrong one wastes work.
| Bronze gib | Wear plate / liner | Rolling linear guide | |
|---|---|---|---|
| Adjustable? | Yes — that is its function | No — fixed thickness, shimmed at most | Preloaded at assembly |
| Stick-slip | Suppressed by solid lubricant | Suppressed by the liner material | Absent — rolling, not sliding |
| Damping | Good | Good | Low |
| Shock and swarf | Tolerant | Tolerant | Sensitive — needs seals and wipers |
| Retrofit | Made to the existing slot | Needs a machined recess | Needs a machined rail seat |
| Typical use | Replacement on existing machines | New build, way rebuilding | High-speed positioning axes |
Where an existing gib is worn, replacing it in bronze is the least invasive repair — the slot is already there and no machining of the casting is needed. Where the way is scored, a wear plate bonded to a rebuilt surface is better. Rolling guides suit new high-speed axes, rarely a retrofit to a slideway designed for sliding.
Where Bronze Gibs Are Used
Centre lathes
Cross-slide and top-slide dovetails, and the saddle on the bed ways. These run slowly, heavily loaded, and are fed by hand for much of their life — the finish on a facing cut depends directly on how smoothly the slide feeds.
Milling machines
The knee on the column dovetail and the saddle under the table carry the cutting load and the workpiece. Climb milling reverses the load direction on the gib, so a strip with no play is what keeps the table from rocking.
Grinders
Table ways and wheelhead slides are where stick-slip shows most, because infeed is measured in microns. Plugged gibs are a common retrofit on surface grinders that will not hold a fine down-feed.
Presses, planers and forging plant
Ram gibs here are large, thick and shock-loaded. Aluminum bronze and manganese bronze wear plates are usual, often in segments so the gib can be replaced without stripping the ram.
Woodworking and stone cutting
Dust and abrasive swarf rule out a rolling guide and contaminate an oil film quickly. Solid-lubricated bronze runs without attracting grit.
Frequently Asked Questions
What is a gib on a machine tool?
An adjustable strip of bearing material fitted between a sliding member and the way it runs on. It sets the running clearance, carries the cutting load into the way, and is the part designed to wear so the machine way does not.
What is an L-gib?
A shop term rather than a standard designation, usually applied to a gib whose section includes a lip or return that locates the strip in its slot. Flat, taper and dovetail are the more precise names for the common forms.
Why does my slide stick and then jump?
Stick-slip. At the low speeds and high loads a slideway sees, an oil film cannot form, so static friction sits well above dynamic friction. The slide holds, the drive winds up, then it releases. A graphite-plugged gib narrows that gap.
Do graphite-plugged gibs still need way oil?
No. Oil does no harm if a way-lubrication system is already running, but it is not required, and on vertical ways where oil drains away the graphite does work the oil cannot.
Can I replace a polymer liner with a bronze gib?
Usually yes, provided the slot has the depth. Polymer liners are thin, so a bronze replacement may be thicker than the space allows. Send the slot depth and available thickness.
How do I know when a gib is worn out?
When the adjusting screw has run out of travel and the slide still has play, or when the slide can be set tight at one end of travel only.
What taper should I specify?
Match the original — commonly around 1:50 to 1:60. The ratio has to match the mating surface or the gib contacts along a line instead of a face. If you cannot measure it, send the old part.
Can you make a gib from a sample rather than a drawing?
Yes — the common route for older machines with no documentation. Send the original part, or a sketch with length, width, thickness at both ends and hole positions from one datum.
Can the sliding face be machined to thickness?
Only lightly. A plugged strip is supplied finished; cutting deep across the plugs closes them with swarf. Machine or scrape the back face.
What quantities and lead times apply?
A single gib is accepted, which is usually the sensible order for a one-off repair. Lead time depends on whether the section comes from stock or has to be cast.
Durable Oil-Free Wear Plates for Heavy-Duty Applications
Email us your production files, or reach out to schedule a call with our expert team.
Email us your production files, or reach out to schedule a call with our expert team.
Email us your production files, or reach out to schedule a call with our expert team.
Email us your production files, or reach out to schedule a call with our expert team.
Email us your production files, or reach out to schedule a call with our expert team.
Email us your production files, or reach out to schedule a call with our expert team.
