JGBF Oilless Ejector Guide Bearings
We provide custom manufacturing of finished bronze parts and self-lubricating bronze, precisely based on our clients’ drawings.
JGBF Oilless Ejector Guide Bearings: Sizes, Materials and Limits
JGBF is a flanged, solid-lubricated guide bushing built for slow, heavily loaded, short-stroke motion — the duty found in ejector and guide systems, where the bearing moves a few millimetres under high load, sits in a hot or dirty cavity, and cannot be greased in service. The body is a high-strength brass with graphite embedded in the working surface. This page covers the construction, the standard size range, the load and speed envelope, and the cases where a different form is the better choice.
What the JGBF construction consists of
- High-strength brass matrix. The body is cast from a high-tensile brass of the Cu–Zn–Al–Fe–Mn type rather than a plain tin bronze, which gives the compressive strength needed when a long pin side-loads over a short engagement length.
- Embedded solid lubricant. A graphite-based solid lubricant is set into the working surface during manufacture, covering roughly 25–30% of the surface area. As the shaft slides, a transfer film forms on the counterface, which is what keeps friction low without any external oil or grease.
- Machined inner and outer surfaces. Both the bore and the outside diameter are finish machined, so the bushing can be pressed into a housing and still hold its clearance. The flange locates it axially and takes thrust from the ejector plate.
The result is a bushing that runs without a lubrication schedule and does not pump grease into the mould cavity. Comparable parts for mould and die duty are listed under graphite-impregnated bronze bushings.
Typical technical data
Typical technical data
The figures below are typical values for this product family and are for first-pass sizing only; the values on the material certificate and inspection report for your batch take precedence.
| Property | Typical value | Notes |
|---|---|---|
| Matrix alloy | High-strength brass, Cu–Zn–Al–Fe–Mn type | Confirm the grade if the drawing names one |
| Solid lubricant coverage | 25–30% of the working surface | Layout is set during manufacture |
| Tensile strength | About 700–800 MPa (100–115 ksi) | Section dependent |
| Hardness | About 200–250 HB | Sets the shaft hardness requirement |
| Maximum dynamic load | Roughly 100 MPa (14 500 psi) | Static capacity is higher |
| Maximum sliding speed, dry | Below about 0.5 m/s (20 in/s) | Short-stroke ejection duty is well inside this |
| PV limit, dry | About 1.0–1.6 MPa·m/s | Check with margin against the worst case |
| Coefficient of friction, dry | About 0.10–0.16 | Depends on counterface and temperature |
| Service temperature | Roughly −40 °C to +300 °C (−40 °F to 570 °F) | Above this the film degrades faster |
Where JGBF bushings are used
Where JGBF bushings are used
The common thread is slow motion under load, with relubrication either impossible or undesirable:
- Injection and die-casting moulds. Ejector plate guide pillars and ejector pin guides, where grease would migrate into the cavity and mark the part — see bronze bushes for injection moulding and die-casting machine bushings.
- Hydraulic engineering. Dam gate guides, hoist sheaves and turbine linkage, where the bearing is washed by spray or submerged. Related parts: hydropower bearings and spherical bearings for dam gates.
- Steel and metallurgical plant. Guide and linkage positions near furnaces, where heat breaks grease down quickly — see sliding bearings for steel plant.
- Automotive and general manufacturing lines. Transfer, stamping and conveyor mechanisms with many guide points and a fixed maintenance window.
- Chemical, paper, textile and food machinery. Locations where oil or grease would contaminate the product.
Limits: when JGBF is the wrong choice
Limits: when JGBF is the wrong choice
- Continuous rotation or higher sliding speed. The dry PV limit is the binding constraint; a rotating shaft with real surface speed needs an oil-lubricated bronze or a rolling bearing.
- Light load at high frequency. Too little load to generate the transfer film makes wear behaviour less predictable.
- Shock loads beyond the material capacity. Brass tolerates impact less well than a steel-backed bearing; check peak load, not only mean load.
- Soft or rough shafts. A hardened, smooth counterface is required, or the bushing will score rather than polish the shaft.
- Sustained temperature above roughly 300 °C (570 °F). The graphite film oxidises faster and the matrix loses strength.
- Strongly acidic or caustic media. High-zinc brass is vulnerable to dezincification and stress corrosion in some environments; a tin bronze or aluminum bronze body is safer there.
- Graphite dust not permitted at the part or in the process, for example in coating or clean operations.
- A different form fits better. For non-flanged guides see the JGB series or the JEGB / JEGBK type; for heavier flanged duty see JOST flanged guide bearings.
Still can’t find it? Ask us directly.
Send the part number, drawing or a photo — we’ll confirm the equivalent grade and quote, usually within one business day.
JGBF Oilless Ejector Guide Bearings Size
| Standard No. | d | L | d G6 | D m6 | D1 | T | L1 | Standard No. | d | L | d G6 | D m6 | D1 | T | L1 | |||||||
| JGBF-12×19 | 12 | 19 | 12 | +0.016 +0.006 |
18 | +0.018 +0.007 |
25 | 4 | 19 | JGBF-35×39 | 35 | 39 | 35 | +0.025 +0.009 |
48 | +0.025 +0.009 |
54 | 10 | 39 | |||
| JGBF-12×24 | 24 | 24 | JGBF-35×49 | 49 | 49 | |||||||||||||||||
| JGBF-12×29 | 29 | 29 | JGBF-35×59 | 59 | 59 | |||||||||||||||||
| JGBF-12×34 | 34 | 34 | JGBF-35×69 | 69 | 69 | |||||||||||||||||
| JGBF-16×19 | 16 | 19 | 16 | 25 | +0.025 +0.009 |
30 | 6 | 19 | JGBF-35×79 | 79 | 70 | |||||||||||
| JGBF-16×24 | 24 | 24 | JGBF-35×89 | 89 | 70 | |||||||||||||||||
| JGBF-16×29 | 29 | 29 | JGBF-35×99 | 99 | 70 | |||||||||||||||||
| JGBF-16×34 | 34 | 30 | JGBF-40×39 | 40 | 39 | 40 | 55 | +0.030 +0.011 |
61 | 39 | ||||||||||||
| JGBF-16×39 | 39 | 30 | JGBF-40×49 | 49 | 49 | |||||||||||||||||
| JGBF-16×49 | 49 | 30 | JGBF-40×59 | 59 | 59 | |||||||||||||||||
| JGBF-20×24 | 20 | 24 | 20 | +0.020 +0.007 |
30 | 35 | 8 | 24 | JGBF-40×69 | 69 | 69 | |||||||||||
| JGBF-20×29 | 29 | 29 | JGBF-40×79 | 79 | 79 | |||||||||||||||||
| JGBF-20×34 | 34 | 34 | JGBF-40×89 | 89 | 80 | |||||||||||||||||
| JGBF-20×39 | 39 | 39 | JGBF-40×99 | 99 | 80 | |||||||||||||||||
| JGBF-20×49 | 49 | 40 | JGBF-40×109 | 109 | 80 | |||||||||||||||||
| JGBF-20×59 | 59 | 40 | JGBF-50×49 | 50 | 49 | 50 | 70 | 76 | 12 | 49 | ||||||||||||
| JGBF-25×24 | 25 | 24 | 25 | 35 | +0.025 +0.009 |
40 | 24 | JGBF-50×59 | 59 | 59 | ||||||||||||
| JGBF-25×29 | 29 | 29 | JGBF-50×69 | 69 | 69 | |||||||||||||||||
| JGBF-25×34 | 34 | 34 | JGBF-50×79 | 79 | 79 | |||||||||||||||||
| JGBF-25×39 | 39 | 39 | JGBF-50×89 | 89 | 89 | |||||||||||||||||
| JGBF-25×49 | 49 | 49 | JGBF-50×99 | 99 | 90 | |||||||||||||||||
| JGBF-25×59 | 59 | 50 | JGBF-50×109 | 109 | 90 | |||||||||||||||||
| JGBF-25×69 | 69 | 50 | JGBF-50×119 | 119 | 90 | |||||||||||||||||
| JGBF-30×29 | 30 | 29 | 30 | 42 | 47 | 10 | 29 | JGBF-60×99 | 60 | 99 | 60 | +0.029 +0.010 |
80 | 86 | 15 | 99 | ||||||
| JGBF-30×34 | 34 | 34 | JGBF-60×109 | 109 | 109 | |||||||||||||||||
| JGBF-30×39 | 39 | 39 | JGBF-60×119 | 119 | 110 | |||||||||||||||||
| JGBF-30×49 | 49 | 49 | JGBF-60×129 | 129 | 110 | |||||||||||||||||
| JGBF-30×59 | 59 | 59 | JGBF-60×149 | 149 | 110 | |||||||||||||||||
| JGBF-30×69 | 69 | 60 | ||||||||||||||||||||
| JGBF-30×79 | 79 | 60 | ||||||||||||||||||||
Frequently asked questions
What does JGBF mean and how does it differ from JGB?
Both are solid-lubricated ejector guide bushings in the same family. JGBF is the flanged version, so the standard list carries flange diameter and flange thickness alongside bore, outside diameter and length.
Can JGBF bushings run completely dry?
Yes, that is the intended duty. The graphite-based lubricant covering 25–30% of the working surface supplies the film. The condition attached is the PV limit: dry running works while load times speed stays inside the envelope.
What shaft hardness and finish are required?
A hardened, ground counterface is standard practice, typically 300 HB or harder with a finish around Ra 0.4–0.8 µm (16–32 µin). Softer or rougher shafts wear the film off and increase the risk of scoring.
Are non-standard sizes available?
Yes. Bore, outside diameter, length and flange dimensions are machined to drawing, and the lubricant layout can be adjusted for the duty — see calculating plug size for graphite-plugged bronze for the layout logic.
How long will a JGBF bushing last in a mould?
Life depends mainly on side load, alignment and temperature rather than on cycle count. Within the PV envelope and with good alignment, service is normally measured in years. Where pins are heavily side-loaded, life drops sharply — measure wear on the first set and set the interval from that.
