Used Internal Grinding Machine for sale (70,919)

Year of construction: 2018, condition: used, overall weight: 10,000 kg, total length: 2,300 mm, total width: 6,500 mm, total height: 2,400 mm, BUDERUS CNC 235 – CNC Grinding and Machining Center Machining / Spindle 2 machining areas / channels Max. machining length: 150 mm Max. swing diameter: Ø 310 mm Workpiece spindle speed: 0–3,000 rpm Spindle bore: Ø 45 mm Ledpfxozwa Rhj Aiysrr Workpiece spindle positioning via C-axis Table speed X/Z: 0–30 m/min Motor Spindle WMZ / DVS Type: GS 205-045/17 Year of manufacture: 2014 Automation Automatic workpiece feed / conveyor system Coolant / Filtration System LIQUI-Filter GmbH System: UR1060 / MW260 / Gamma 13 Tank capacity: 2,400 l Year of manufacture: 2015 Cooling System HYFRA gamma 13-F-S Cooling capacity: 13 kW at 32 °C Year of manufacture: 2015 Measuring Technology JENOPTIK post-process measuring technology Year of manufacture: 2018 Supply Data 3 × 400 V / 50 Hz Installed power: approx. 45 kW Compressed air requirement: 15 Nm³/h at 5 bar Control: Siemens SINUMERIK 840D Travel Z-axis: 300 - mm Workpiece diameter over bed max.: 150 mm Weight approx.: 10,000 kg Dimensions (LxWxH) approx.: 2300 x 6500 x 2400 mm Travel X-axis: 1240 - mm Year of construction: 2,018 Condition: good Terms of payment: 100% prepayment before pick-up Terms of delivery: Free loading on truck under power: No

Condition: ready for operation (used), Year of construction: 2020, Taiwan Palmary Surface Grinding Model : PSG-C60100AHR Lodpfx Asy N Rkxeiysrr Year 2020 Max. Grinding surface 1,000mm x 600mm Electro-Magnetic chuck MPG Overhead Dresser Automatic grinding cycle 0.001mm - 0.03mm auto grind Spindle 1,750 rpm Wheel dia.405x50x127mm Good Operational

Condition: refurbished (used), Year of construction: 2023, operating hours: 3,000 h, functionality: fully functional, center height: 180 mm, workpiece weight (max.): 200 kg, grinding length: 1,000 mm, center width: 1,000 mm, grinding wheel diameter: 500 mm, total width: 2,600 mm, total length: 4,700 mm, total height: 2,200 mm, grinding diameter: 300 mm, workpiece weight between centers: 2,00,000 g, type of input current: three-phase, workpiece diameter between centers: 300 mm, workpiece length between centers: 1,000 mm, grinding wheel width: 100 mm, spindle speed (max.): 1,200 rpm, spindle speed (min.): 10 rpm, feed length X-axis: 320 mm, feed length Z-axis: 1,100 mm, feed rate X-axis: 1,000 m/min, feed rate Y-axis: 1,500 m/min, grinding spindle speed: 1,700 rpm, overall weight: 7,500 kg, pivoting range: 30 °, warranty duration: 12 months, year of last overhaul: 2023, input frequency: 50 Hz, rapid traverse X-axis: 1,000 m/min, rapid traverse Z-axis: 1,500 m/min, input voltage: 400 V, Schaudt PF43 U1000, manufactured in 1994, retrofitted (premium refurbished) by GSN in 2023. Siemens Sinumerik 840 D SL control system. Low operating hours, approximately 3000 hours since the retrofit. MK4 workpiece spindle, MK4 tailstock. Grinding travel: 300mm Workpiece length, including clamping devices, at maximum grinding travel: 450mm Grinding wheel dimensions: 500x100mm Bore diameter: 203.2mm Controlled workpiece circumferential speed (WUG) SUG external cylindrical grinding spindle: 45m/s Freely positionable, automatic B-axis Machine with new, fully enclosed splash guard Ljdpfxszcfnqs Aiyerr GSN measuring head Diatronic 22 including C2 and W axes/turret Touch probe sensor with hydrophone (water jet) including collision monitoring Tailstock retrofitted with automatic cylinder error compensation Clamping/unclamping adjustable via hydraulic clamping device Upgrade to a 15" screen on the control panel NEW PRICE GROSS 2023: €407,432.20 plus additional tools, etc.

Condition: good (used), Please refer to the images for all technical specifications. Transport and loading can be arranged throughout Europe for an additional charge upon request. Prices are subject to VAT. Viewing is possible by appointment. Contact us—our team looks forward to assisting you. Machinery purchase / sale PURCHASE / SALE OF PRODUCTION & METALWORKING MACHINES, MACHINE TOOLS, AND MUCH MORE. Do you need a high-quality yet affordable machine for your production? Or are you looking to sell yours? Ljdpfx Aiszvnnfeysrr For further information or contact options, please reach us via the contact form.

Condition: as good as new (ex-display), Year of construction: 2025, functionality: fully functional, grinding length: 500 mm, grinding width: 250 mm, Young, like-new demonstration machine: High-precision surface grinding machine, "Optimal" series, available at a special net price. Grinding area: 500 x 250 mm Features: ● Surface grinding machine with automatic vertical feed ● Grinding sequence: roughing – finishing – spark-out ● Siemens S700 touchscreen panel and electronic handwheel for Y-axis ● Digital display for vertical axis Y and cross axis Z ● Table cover and splash guards in stainless steel design ● Electrical cabinet fitted predominantly with Siemens components ● Includes manual dressing device, electro-magnetic chuck, and coolant filtration system Main technical data: Grinding length mm 500 Grinding width mm 250 Distance table surface to spindle center mm 450 Table drive Hydraulic Table load kg 180 Longitudinal movement X Table speed, steplessly adjustable m/min 7 – 23 Max. longitudinal travel mm 560 Cross movement Z Max. travel speed mm/min 990 Max. cross travel mm 275 Vertical movement Y Max. travel speed mm/min 460 Grinding spindle / Grinding wheel Spindle power kW 2.2 Wheel dimensions mm 200x20x31.75 Spindle speed (speed control optional) min⁻¹ 2850 Dimensions Machine weight (net) kg 1800 Machine dimensions (inc. reciprocation) Width mm 2300 Depth mm 1650 Height mm 1680 Power connection kW 3.7 All model series include standard accessories: ● 1 standard grinding wheel ● 1 wheel flange ● 1 dressing block with diamond ● 1 balancing arbor Lsdpfx Aijyak Dloysrr ● 1 balancing stand ● 1 machine lamp ● 1 set of machine tools ● 1 set of documentation with spare part list ● Machine in CE-conform (metric version) Precision and surface quality at optimal price. Fully equipped for universal use in a wide range of industrial and application areas. Machine comes with a 12-month parts warranty. By the way, aside from affordable new and certified used machines, we offer even more: • On-site consultation and solution finding • Organization of machine transport to your facility • Installation, commissioning, and turnkey handover • Spare parts supply • Control training for Siemens, Heidenhain, and Fanuc • Trained service staff available in your area and more • 24/7 telephone support • Tax-optimized trade-in of your old machine • Attractive financing options, even without down payment

Condition: reconditioned (used), Year of construction: 1970, functionality: fully functional, Table size 800 x 200 mm Magnet table 600 x 200 mm Grinding capacity 630 x 200 mm Max grinding high 320 mm Dia of grinding wheel max:250 mm Spindle speed 2750 rpm Power required 3,6 kW Weight 2200 kgs Dimensions L x W x H =: 1900 x 1500 x 2000 mm Dimensions of coolant tank L x W x H = 400 x 300 x 500 mm Ljdpfxew R Dnxs Aiyjrr

Condition: ready for operation (used), HAGEN & GOEBEL / Internal thread cutting machine -Type HG 22 EB -Speed range 180 - 1120 rpm -Thread size up to max. M22 / steel -Thread size / cast iron up to max. M 27 -Thread size aluminum / brass max. M 33 -Smallest thread size M6 -Single stroke / continuous stroke -Table dimensions 600x500mm Dimensions: L x W x H 1.1 x 0.7 x 2 meters / Weight 1000 kg Lrsdpfx Aszu Nzweiysr Errors and omissions excepted.

Year of construction: 2015, condition: new, functionality: fully functional, machine/vehicle number: 051, We offer this new Kohlbacher BARACUDA 750 side grinding machine for band saws, year of construction 2015. Manufacturer: Kohlbacher GmbH Model: BARACUDA 750 Serial number: 05N Type: BARACUDA 750 Manufacturing date: 06/2015 Construction year: 2015 Condition: new Technical details: - CNC control - Bosch Rexroth controller - Central electrical blade height adjustment - Saw blade clamping system, clamps the blade automatically tight when grinding - Grinding wheel is direct driven, eliminates vibrations and deep pass (heavy removal) operation is possible - Grinding heads are guided by pre loaded ball rail systems to assure optimum accuracy - Width of band saw blades 30 – 260 mm - Blade thickness 0,6 – 2 mm - Pitch min./max. 15 – 60 mm - Working speed 0 – 12 Teeth/min. Lodpfozuc Uqex Aiyerr - Grinding wheel diameter 125 mm CBN - Grinding wheel motor 2 x 1,5 kW - Pump cooling system 60 l/min. - Weight 1050 kg If you have any questions or need more information, feel free to send us a message or give us a call.

Condition: good (used), Year of construction: 1972, max. wheel diameter 80 mm Lodpfx Ajw N S D Seiysrr gear width 60 mm max. module 3 min. module 0,1 total power requirement 0,4 kW weight of the machine ca. 120 kg dimensions of the machine ca. 0,6x0,6x0,75 m

Condition: repair required (used), Year of construction: 1981, grinding length: 6,600 mm, grinding width: 520 mm, grinding height: 260 mm, table width: 550 mm, grinding spindle motor power: 52,000 W, We are offering this Göckel G 80 eL surface grinding machine, manufactured in 1981, which requires repair. Ledozvqh Ujpfx Aiyjrr Manufacturer: Gustav Göckel Maschinenfabrik GmbH D-6100 Darmstadt Machine type: G 80 eL Serial number: 6062 If you have any questions or would like more information, please feel free to send us a message or call us. - Grinding length: 6600 mm - Width: 550 mm - Magnet width: 300 mm - Grinding width: 520 mm - Grinding height: 260 mm - Grinding height at right angles: 150 mm - Grinding motor: 52 KW Please note: the machine is delivered without a water tank. Pumps, hoses, and accessories are included.

Condition: used, Year of construction: 1990, grinding diameter max. 1-150 mm Lrsdjztfz Dopfx Aiyer regulating wheel width 100-200 mm weight 5 t

Condition: new, Year of construction: 2024, functionality: fully functional, Universal CNC cylindrical grinding machine for high-precision internal & external cylindrical grinding MBF 453U from the MaiBase platform The machine is a completely new development with strong dimensions in a small space! Technical data: Center width: 430 mm Standard center height: 200 mm Grinding length: 400 mm Grinding wheel diameter: 500 mm Z-axis adjustment path: 550 mm X-axis travel: 385 mm Dimensions and weight: 2200 x 2500 x 2400 mm // 6500 kg Equipment of the machine: - FANUC Oi-F Plus control system - Grinding headstock (swiveling) with 15kW motor spindle - Workpiece headstock MK5 - Tailstock MK3 with 20 mm stroke (optional 60 mm / 120 mm) - Handwheel for manual axis movement Lrsdpfx Aotrf Smjiyjr - Z-axis - X-axis - C-axis - B-axis - Glass scales for X- and Z-axis - Internal grinding spindle FISCHER UJ80 - Internal grinding spindle (GMN motor spindle) optional - Dressing spindle attached to the workpiece headstock for rotary dressing - Automatic door drive

Condition: ready for operation (used), Year of construction: 1998, Available immediately, ex works: Console milling machine REFORM Type UF 32 Year of manufacture 1998 Lsdpfx Aezvv N Rjiyerr Table 1400 x 300 mm Travel distances X/Y/Z 1100/300/520 mm SK 50 Spindle speeds 31.5 – 1400 rpm Drive power 7.5 kW Digital display Hydraulic vice Weight 2.7 tons Many tools, milling cutters Price: Euro 3,000.00 plus VAT, ex works

Year of construction: 2024, condition: ready for operation (used), An almost like-new and high-precision CNC centerless grinding machine Monzesi is available. Grinding wheel outer diameter min./max.: 406mm/280mm, inner diameter: 152mm, max. width: 200mm, speed: 2100rpm, power: 11kW. Regulating wheel outer diameter min./max.: 160mm/254mm, inner diameter: 115mm, max. width: 200mm, speed: 285rpm. Workpiece diameter: 100mm, workpiece length: 200mm, regulating wheel axial adjustment: +/-10mm, taper setting: -2°/6°, tilt adjustment: +/-5°, accuracy: 0.0001mm. Machine dimensions X/Y/Z: approx. 3800mm/2000mm/21500mm, weight: approx. 4500kg, control: CNC Fanuc 35i-B Digital, operating hours April/2026: 481h. Documentation available. An on-site inspection is possible. Expected to be available from end of July/August 2026. Lodpjyyb Tlofx Aiyorr

Condition: used, Year of construction: 2005, grinding diameter max. 500-600 mm regulating wheel width 100-200 mm weight 5 t grinding diameter 1-150 mm grinding wheel width 150–250 mm mm Lrodpsztfzqefx Aiyer with water treatment

Condition: used, Year of construction: 2020, controller manufacturer: Sonstige, controller model: WEISS CNC, _____ Description: Year of manuf. : 2020 Control : Sonstige WEISS CNC Centre width : 650 mm In Generel: ear of construction:2020 Control system:WEISS CNC Centre width:650 mm Centre height:200 mm Grinding wheel dimensions:400x60 mm + 500x60 mm Workpiece headstock: Speed:10 -650 rpm Workpiece weight max.:250 (100) kg Sanding diameter max.:390 mm Mounting:MK4 Grinding headstock: Peripheral speed:20 - 50 m/s Grinding disc dimensions right:500 x 60 mm Grinding disc dimensions left:400 x 60 mm X-axis:380 mm Z-axis:700 mm B-axis:torque motor, infinitely variable Tailstock: Pinole diameter:50 mm Pionole stroke:45 mm Mounting:MK 4 Cylinder fine adjustment:+/- 0.04 mm Equipment: Positioning sensors:Direct scales Grinding spindles:2x grinding spindle (left/right) Lsdpszvt Iqefx Aiyerr GAP / Crash Controll:Structure-borne sound (Sensotronik) Balancing:MPM balancing device Workpiece measurement:Marposs PF ME Automation:Robot interface prepared Set-up mode:Electronic handwheel Emulsion mist separator:Mechanical Dresser:For external grinding wheel left/right Accessories:Various grinding discs + flanges

Condition: excellent (used), Year of construction: 2010, grinding length: 330 mm, grinding wheel diameter: 250 mm, total width: 1,765 mm, total length: 1,830 mm, total height: 2,441 mm, grinding diameter: 20 mm, type of input current: three-phase, workpiece diameter between centers: 20 mm, spindle speed (max.): 10,000 rpm, feed length X-axis: 29 mm, feed length Y-axis: 350 mm, feed length Z-axis: 100 mm, feed rate X-axis: 29 m/min, feed rate Y-axis: 350 m/min, feed rate Z-axis: 100 m/min, grinding spindle motor power: 9 W, grinding spindle speed: 7,600 rpm, overall weight: 3,000 kg, input frequency: 50 Hz, rapid traverse X-axis: 15 m/min, rapid traverse Y-axis: 15 m/min, rapid traverse Z-axis: 15 m/min, input voltage: 400 V, workpiece spindle speed (max.): 3,000 rpm, Equipment: rotational speed infinitely variable, Rollomatic ShapeSmart NP5 — CNC cylindrical grinding machine (pinch/peel) with 3-axis loading robot Year of manufacture 2010 · CNC pinch/peel cylindrical grinding machine · Ø 0.025–20 mm · 3-axis loading robot Five-axis pinch/peel cylindrical grinding machine from Rollomatic SA (Le Landeron, Switzerland) for the rough and finish machining of cutting tools, punches, micro-drills, and forming and ejector pins. The original factory invoice from Rollomatic from 2010 for this machine is available, which documents the design, drives, axis travels, and included equipment. KEY DATA - Grinding diameter Ø 0.025 – 20.0 mm · Shank diameter Ø 1.0 – 20.0 mm · Grinding length max. 330 mm - Control system GE FANUC 320iA, 8 axes (5 machine axes + 3 robot axes), NanoGrind user interface on PC - Roughing spindle 8.5 kW, wheel Ø 250 mm, max. 7,600 min⁻¹ · Finishing spindle 1.4 kW, wheel Ø 150 mm, max. 10,000 min⁻¹ - Workpiece spindle with collet chuck W20, 0 – 3,000 min⁻¹ - Axis travels Y 350 mm · Z 100 mm · X and V each 29 mm with glass scale, resolution 0.00005 mm - Loading robot 3 axes, workpieces Ø 1.0 – 16.0 mm, length 30 – 300 mm, magazine 150 – 1,000 pieces - 1830 × 1765 × 2441 mm · approx. 3,000 kg · 3 × 400 V, 50 Hz, max. 15 kW Ledpozvh Uxefx Aiyorr WHAT MAKES THIS MACHINE SPECIAL - Pinch/peel process: Roughing and finishing wheels engage with the workpiece simultaneously — high accuracy of roundness and short cycle times in one pass SCOPE OF DELIVERY - Machine complete: Machine bed, full splash guard, electrical cabinet, pneumatics unit, control panel with 15" screen and PC keyboard - Control system GE FANUC 320iA with 8 axes, Rollomatic NanoGrind user interface on PC - P4Smart software for offline programming and simulation - Roughing station with 8.5 kW spindle (90° design) and finishing station with 1.4 kW direct drive spindle, both with PerfectArbor mounting - Monoblock shank guide with pneumatic pressure lever - Workpiece spindle with collet chuck W20 - Integrated three-axis loading robot with base plate for Rollomatic cassettes - Cassettes and collet chucks from the machine's inventory — the exact scope will be listed definitively for the shipping date - Transport-safe packaging on a wooden pallet, loading onto your truck included - Coolant filter and cooling system as well as extraction are not included in the scope of delivery — both were centrally installed at the previous owner - Fire extinguishing system and grinding wheels are not included in the scope of delivery AVAILABILITY AND INSPECTION Availability: End of September 2026, ex warehouse Velten. Demonstration, trial grinding and measurement only after prior appointment — installation and commissioning will be carried out by an external service partner. PROCESSING Location 16727 Velten near Berlin (Germany) · FCA Velten incl. loading · 100% prepayment · Delivery 1–2 working days after payment receipt · Price on request · All technical data in the attached data sheet. Technical data according to manufacturer's documents (Rollomatic factory invoice from 2010 for this machine and series catalog) — information provided, no agreement on characteristics within the meaning of §§ 434, 443 BGB. We will confirm individual values definitively during the inspection or upon specific request. Subject to errors and prior sale.

Year of construction: 2021, condition: ready for operation (used), A Timesavers (Grindingmaster) wide belt grinding machine with two upper wide belt grinding units and one brushing unit is available. Contact roller diameter: 180mm/280mm, grinding belt accuracy: 0.01mm, brushing unit outer diameter: 300mm, brush oscillation: 150strokes/min, brush motor speed range: 8m-22m/s, table height adjustment: 1mm-100mm, grinding belt dimensions X/Y: 1630mm/2620mm. Machine dimensions X/Y/Z: approx. 4300mm/2650mm/2650mm, weight: approx. 5500kg, control: Siemens PLC. Including one IEP nanofilter cartridge extraction system. Documentation vorhanden. An on-site inspection is possible. Ledpfx Aisy D Tq Rsyerr

Condition: excellent (used), Year of construction: 2021, machine/vehicle number: 8398, functionality: fully functional, power: 15 kW (20.39 HP), input voltage: 400 V, input current: 32 A, input frequency: 50 Hz, type of input current: three-phase, grinding belt width: 150 mm, grinding belt length: 2,500 mm, actuation type: mechanical, total height: 2,200 mm, total length: 3,800 mm, total width: 2,000 mm, Equipment: CE marking, documentation/manual, Löser external cylindrical grinding machine for grinding the outer circumference of pipes 1.3. Technical data Dimensions: Width approx. 3.8 m | Height approx. 2.2 m | Depth approx. 2.0 m Power supply Electrical connection: 3 x 400 V AC | 50 Hz Total power: 15 kW Fuse: 32 A Pneumatic connection Main supply: 6 bar | approx. 5 m3/h Supply for air nozzles: 6 bar | approx. 30 m3/h Workpieces that can be processed Pipes made of steel or stainless steel with the following dimensions: Length: from 10 mm to 100 mm Diameter: from 50 mm to 1000 mm Grinding station type L Number of grinding stations: 1 Grinding mode: Wet machining Grinding technology: Grinding with a grinding belt and contact wheel | Grinding with a grinding wheel Cutting speed: continuously adjustable | max. 30 m/s Power: 7.5 kW per station Current consumption: maximum 14 amps per station Dimensions of grinding belt: Width 150 mm | Length 2,500 mm Dimensions of contact wheel: Width 150 mm | Diameter 400 mm Dimensions of grinding wheel: Width 150 mm | Diameter 400 mm Belt tension: Pneumatic | manually adjustable Station positioning: Manual Workpiece transport Workpiece support: V-groove | Angle 120° Height adjustment of V-groove: Manual Feed devices: 1 Positioning of feed device: Manual Feed speed: approx. 1 m/min to 10 m/min; depending on the workpiece diameter Coolant management The machine is prepared for wet machining. A Stevens paper band filter, type PF 120, machine no. 322177, is included in the scope of supply. Lrjdpfxjzvn Uro Aiyor

Condition: ready for operation (used), Year of construction: 2016, total length: 2,600 mm, total width: 1,600 mm, BUSETTI F10 Lrsdpfezunbpsx Aiysr USED, EXCELLENT CONDITION 2016 COLLECTION IN WROCLAW

Condition: used, • Grinding machine for straight edges. Equipped with two processing stations. Depending on the selected diamond grinding wheel, the desired profile is created and polished. All settings are easily and conveniently adjusted from the front (cup wheel, material removal rate, angle of attack). • Serial number: 84082 • Width – 0.90 m • Infeed – 1.40 m, Outfeed – 1.40 m • Machine length – 1.33 m • Height – 2.05 m • Overall length – 4.13 m • Weight 1050 kg • Price: Available upon request. Lrodpezr Iyajfx Aiyjr

Condition: used, Year of construction: 2003, CNC External Cylindrical Grinding Machine: total connected load 67 kW, voltage 3x400V 50Hz, nominal current 121A, weight approx. 9500 kg Data Ljdpfjzwf Uxex Aiyorr Kelvin Chiller (Model KRA45): serial number 0304666, year 2003, cooling capacity 4500W Data Ritz Coolant Pump (Type F2506): serial number 3196140, manufactured in 1994, 2.9kW

Year of construction: 2016, condition: ready for operation (used), A Jung CNC surface and profile grinding machine is available. Grinding dimensions X/Y: 300mm/600mm, table dimensions X/Y: 300mm/1000mm, spindle center to table distance: 150mm-600mm, max. table load: 400kg, table height: 925mm, travel X/Y/Z: 600mm/450mm/345mm, feed rate X: 40m/min, feed rate Y/Z: 4m/min, grinding spindle speed: 5000rpm, max. grinding wheel dimensions X/Y/Z: 400mm/60mm/127mm. Machine dimensions X/Y: approx. 3300mm/2300mm, weight: approx. 4500kg, control: Siemens 840D sl. Including accessories. Documentation available. An on-site inspection is possible. Lodpfszg Iqnox Aiyerr

Condition: used, Technical details: grinding length: 300 mm Lsdpfx Aijzaunzeysrr centre height: 175 mm swing diameter: 315 mm table clamping surface LxW: 1.800 x 200 mm control: Heidenhain Longitudinal adjustment of grinding unit on table max.: 1100 mm work piece spindle speed: 3steps/1500-2200 U/min feed continuous: 0,001-1 mm Max. travel x-axis: 300 weight of the machine ca.: 3,1 t dimension machine approx.LxWxH: 2,9 x 1,6 x 1,4 mm Swivel for right and left machining Automatic table reversal Tailstock: MK3 holder Operation: Manual control unit/foot switch Coolant: System with feed Heidenhain measuring device *

Condition: used, Year of construction: 1986, Surface Grinding Machine MONOPRECIS 1DR - #2 Travel X: 400 mm Travel Y: 150 mm Lodjzwgrrjpfx Aiyjrr Maxi grinding height (Z): 220 mm Year of construction: 1986 Axes X - Y - Z manual Magnetic chuck: manual / tilted Magnetic chuck dimensions: 255 x 130 mm Grinding wheel dimensions: Ø max 170 mm Voltage: 380 V Dimensions (L x W x H): 1300 x 1100 x 1600 mm Weight: approx 500 kg