Used Cylindrical Grinding Cnc for sale (12,633)

Condition: used, Year of construction: 1992, Technical details: Tjdpfor R Ek Ssx Ahusf grinding diameter: 50 mm grinding length: 100 mm centre height: 100 mm centre distance: 200 mm

Condition: used, Year of construction: 2023, functionality: fully functional, machine/vehicle number: 1045-0282, center height: 175 mm, center width: 1,000 mm, grinding wheel diameter: 500 mm, CNC Universal External Cylindrical Grinding Machine S33 Machine No.: 1045-0282 Year of Manufacture: 2023 Centre Distance: 1000 mm Tsdpfexy E Rlox Ahuef Centre Height: 175 mm Location: Factory Switzerland. Contact us for a detailed offer.

Condition: ready for operation (used), Year of construction: 1989, CNC Universal Cylindrical Grinding Machine TOS Model: BUA 25 x 1000 Tjdjx Andgopfx Ahujf Year of manufacture: 1989 Completely overhauled and equipped with a new control in 2007, has only been operated occasionally since then Swing diameter: 280 mm Maximum grinding diameter: 250 mm Grinding length: 1000 mm Fitted with a new 2-axis CNC Teach-In control KAVALIR K 51/2 Ball screw spindles, axis drives, and measuring systems on both axes Grinding wheel: 400 x 40 x 127 mm Workpiece spindle speed steplessly adjustable from 30 to 150 rpm Grinding wheel speed: 2036 – 2556 rpm Workpiece spindle head swivels 90 degrees Table swivels plus/minus 9 degrees Internal grinding device Flanges Belt filter system Weight: 5 tons Complete set of accessories Price: EUR 7,500.— plus VAT, ex location

Condition: excellent (used), Year of construction: 2009, functionality: fully functional, The STUDER S242 is a versatile hard-fine machining center for grinding, turning, and milling operations on medium-sized workpieces. It is ideal for complete machining in a single setup – from external and internal grinding to hard turning and drilling/milling with driven tools. With the Studer S242, workpieces in the rotational sector can be finished to very high precision. Thanks to integrated automation, this machine is suitable for both single-part and series production. The S242 is also equipped with a VDI turret featuring driven tools. Center distance: 800 mm Swing diameter: 180 mm Max. workpiece weight: 60 kg X-axis: travel 220 mm, resolution 0.00001 mm Z-axis: travel 1,600 mm, resolution 0.00001 mm Grinding spindle: 6.8 kW, grinding wheel Ø 400 x 50 mm, automatic balancing Tedpfjw Hqm Ijx Ahuef Workpiece spindle head: AC synchronous spindle motor 10.5 kW, up to 7,500 rpm Tailstock variants: quill tailstock with integrated position measuring system Machine bed: Mineral cast Granitan® S103 for excellent damping and thermal stability Software & Control: Fanuc 31i-A control with 15" touchscreen Dialog language: German for StuderWIN Integrated measuring control with Renishaw LP2 touch probe, switchable to the turret Special features & advantages: Complete machining in a single setup → reduced main and secondary times High dimensional accuracy and surface quality due to Granitan® machine bed Short changeover times, suitable for everything from single-part to large-series production Flexible clamping system and modular tool configuration High process reliability thanks to integrated measuring and sensor systems Dimensions & Weight: Total weight: 12,000 kg Connected load: 45 kVA Compressed air requirement: min. 5.5 bar

Condition: reconditioned (used), Year of construction: 2008, functionality: fully functional, center height: 175 mm, type of input current: three-phase, spindle speed (max.): 1,500 rpm, spindle speed (min.): 1 rpm, feed length X-axis: 285 mm, feed length Z-axis: 800 mm, overall weight: 4,000 kg, rapid traverse X-axis: 5 m/min, rapid traverse Z-axis: 10 m/min, input voltage: 400 V, CNC Cylindrical grinder STUDER S33 TECHNICAL CHARACTERISTICS: Year of manufacturing: 2008 CNC control: FANUC 21i-TB Software installed: StuderGrind Centre distance: 650 [mm] Height of centers: 175 Stroke X axis: 285 [mm] Min. Stroke speed X axis: 0.001 [mm/min] Max. Stroke speed X axis: 5000 [mm/min] Resolution X axis: 0.0001 [mm] Stroke Z axis: 800 [mm] Min. Stroke speed Z axis: 0.001 [mm/min] Max. Stroke speed Z axis: 10000 [mm/min] Resolution Z axis: 0.0001 [mm] B axis swivelling stroke: -15 [°] / +195 [°] B axis indexing precision: Hirth 1 [°] Workpiece spindle nose: MT5 Workpiece spindle min. speed: 1 [rpm] Workpiece spindle max. speed: 1500 [rpm] Max. part weight in part holder headstock between centres: 80 [Kg] Type of attachment tailstock: MT3 Tailstock quill stroke: 35 [mm] Tailstock quill diameter: 50 [mm] Tailstock fine adjustment: +/- 40 [mm] Supply voltage: 400 [V] Total power required: 20 [kVA] Weight: 4000 [Kg] INCLUDED EQUIPMENT: x1 internal grinding spindle type 102560B – speed: 60,000 [rpm] x1 hydraulic swiveling dressing attachment x1 fixed dressing unit mounted on the table x1 rotating wheel dressing unit (electrical) x1 3-jaw chuck Ø170 [mm] - MT5 x1 4-jaw chuck Ø170 [mm] - MT5 x1 magnetic chuck Ø170 [mm] - MT5 x1 2-point steady rest x1 pneumatic tailstock lift x1 pneumatic upper-table lift x1 longitudinal slide with rotary table - swiveling up to 8.5 [°] x1 automatic B-axis turret wheelhead – Hirth gearing 1 [°] x1 C-axis for thread and form grinding x1 workpiece probe MOVOMATIC C25 x1 contact control device DITTEL SENSITRON 6 x1 semi-automatic wheel balancing device MPM type BMT100M x1 paper filtration unit ARO TECHNOLOGIES type 5491.246A01 Tjdpfxexywhpe Ahusf x1 mist extraction unit AIR-FRESH SERVICE type FMN-V12 x1 foot pedal x1 electrical cabinet air conditioner x4 external grinding wheel flanges x1 set of lifting equipment x1 axis bracket (for transportation of the machine) x1 set of operating manuals (French, English, and German) More information upon request.

Condition: ready for operation (used), Year of construction: 2013, functionality: fully functional, Cylindrical grinding machine – external / Manufacturer: WMW / Type: SA 6U x 3000 / YOM/Completely overhauled: 2013 (machine overhauler/carried out by SerWeMa/Germany) Range of parts: Straightening rollers, grinding spindles, general shaft machining. Tjdpfxjxymdas Ahuef Special feature: Machining with up to 6 steady rests. The machine can be inspected under power by appointment. TECHNICAL DATA: Working range: - Centre height: 260 mm - Max. swing diameter: 515 mm - Max. grinding length: 3.000 mm - Max. grinding diameter: 515 mm - Max. workpiece weight: 500 kg Workpiece headstock: - Speed continuously variable: 12.5 - 355 rpm - Centring tip: Morse K5 Tailstock: - Max. quill stroke: 40 mm - Centring tip: Morse K5 Grinding headstock: - Grinding wheel: * Max. outer diameter: 630 mm * Width max.: 125 mm EQUIPMENT: - Extraction system - Documentation - CE marking No guarantee is given for the completeness and accuracy of the technical data and equipment. - Subject to prior sale -

Condition: used, Year of construction: 2006, Technical data: Working ranges: X-axis: 1870 mm Y-axis: 400 mm Z-axis: 560 mm C-axis speed: 3000 rpm Max. grinding area: 1700 x 620 mm Tedpfx Ahsxzq I Sjusf without table dresser: 1500 x 620 mm Table dressing device, diamond wheel: ø 110 mm Grinding wheel diameter: 400 mm Max. width: 100 mm Grinding wheel bore: 127 mm Distance table to spindle center: 800 mm Table height: 900 mm Max. table load: 2200 kg Weight, approx.: 12,000 kg Equipment: - Siemens SINUMERIK 840D control, OPO12 operator panel - Measuring system - Electro-magnetic clamping plate - Full enclosure - Central lubrication - Mist extraction - Clamping system for automatic wheel change - Coolant unit - Coolant recirculating chiller - Profiling device Water treatment system available at additional cost

Condition: reconditioned (used), KELLENBERGER KEL-VISTA UR 175X600 is a CNC cylindrical grinder engineered for precision, high accuracy and reliability. Capacity: centre height 175 mm; between centres 800 mm; grinding length 600 mm; max Ø 349 mm; max weight 100 kg. Key specs: Z 750 mm; X 320 mm; left wheel Ø400×80×127, right Ø300×40×127; wheel speeds 875–1900 rpm (stepless); wheel motor 5 kW; work spindle 8–800 rpm (stepless), taper 5 CM; rapid 12 m/min; air 6 bar; 3×400 V 50 Hz; machine ≈3000 kg; 3200×1700×2000 mm. Accessories: coolant, coolant-through-spindle (IKZ), paper filter, MARPOSS probe, MOVOMATIC measuring control, internal grinding attachment, balancing, RS‑232. Suited for tight tolerances in automotive, watchmaking, machine tools, aerospace, medical. Tedpfx Ahoxx U Tasuef

Condition: used, Year of construction: 1981, Technical details: grinding diameter: 240 mm grinding length: 700 mm centre height: 125 mm table length: 1525 (schwenkbar) mm distance grinding spindle - table min./max.: 225/410 mm rpm speed range - grinding wheel: 1590 U/min grinding wheel dia. (unused wheel): 600 mm Tedpfsu Ng Avox Ahusf grinding wheel dia. (used wheel): 450 mm cutting speed: 50 m/s total power requirement: 13 kW weight of the machine ca.: 5,5 t space requirements of the machine approx.: L:2,8xB:2,2xH:1,8 m Cylindrical grinding machine, semi-automatic operation - grinding spindle head -adjustment 185mm - grinding spindle head-infeed 0,001-0,05 mm/min continuous - rotation workpiece 50-500 rpm continuous machine is equipped: - sleeve with hydr. retraction - cooling device - trueing device - grinding wheel balancing - transverse delivering device for grinding spindle head - hydr. adjustment of grinding table. Upper table swivable. Documentation i.D. *

Condition: good (used), Year of construction: 1974, Ref. -No.: 10159 Manufacturer: KELLENBERGER Type: 1000 U Year of construction: 1974 Storage location: Halberstadt Todpexxn Udefx Ahujf Country of origin: Schweiz Grinding Length: 1000 mm Grinding Diameter: 250 mm

Condition: good (used), Year of construction: 2006, functionality: fully functional, center height: 100 mm, workpiece weight (max.): 35 kg, grinding length: 500 mm, grinding diameter: 125 mm, overall weight: 1,800 kg, input voltage: 400 V, For sale: 1 used grinding machine. Manufacturer: Knuth Werkzeugmaschinen GmbH. Model: RSM 500. Year of manufacture: 2006. Technical data: Centre height: 100 mm; Max. grinding diameter: 125 mm; Distance between centres: 520 mm; Max. grinding length: 500 mm; Max. workpiece weight: 35 kg; Internal grinding diameter: 10 - 40 mm; Internal grinding depth: 50 mm; Spindle taper: MK4; Tailstock: MK2; Weight: 1,800 kg. Documentation available. The machine can be inspected at our warehouse in 09599 Freiberg. Tedpfxsxzrvws Ahuof

Condition: used, Year of construction: 1980, Technical details: grinding diameter: 380 mm grinding length: 1000 mm centre height: 180 mm grinding wheel diameter: 400 mm max. workpiece weight between centres: 250 kg total power requirement: 10 kW weight of the machine ca.: 4,1 t dimensions of the machine ca.: 3 x 2 x 1,6 m with internal grinding attachment with fixed and swivelling headstock with coolant tank * Tsdpfewy Ri Njx Ahusf

Condition: ready for operation (used), Year of construction: 2007, operating hours: 11,960 h, functionality: fully functional, machine/vehicle number: 2416, grinding length: 1,500 mm, overall weight: 24,000 kg, TECHNICAL DETAILS Grinding length: 1,500 mm MACHINE DETAILS Dimensions & Weight Space requirement: 3,900 x 3,500 x 2,500 m Machine weight: 24 t Operating Hours Operating time: 21,727 h Production time: 11,960 h Todpsxvxn Aefx Ahujf EQUIPMENT Hoffmann KSM filter system 2 spare measuring heads Marposs S/500 Prismatic supports

Condition: used, KELLENBERGER KEL-VARIA R175 x 1500 is a CNC cylindrical grinder engineered for high precision, top accuracy and reliable production. Capacities: centre height 175 mm, distance between centres 1500 mm, Z-axis 1650 mm, workpiece weight on centres max. 150 kg; grinding wheel Ø500×80 mm (bore 203 mm) or Ø400×63 mm (bore 127 mm); max wheel travel 320 mm. Key specs: wheel speeds stepless 1000–2150 rpm (peripheral speed 45 m/s); feed 7500 mm/min; work spindle swivels -10/+100° with 8–800 rpm; permitted load 160 Nm; grinding spindle motor 7.5 kW; work spindle motor 2 kW; 3×400 V 50 Hz; rapid 15 m/min; approx. weight 6000 kg; dimensions 4700×2300×2000 mm; air 6 bar. Accessories: coolant system, paper filtration, MARPOSS touch probe, set of grinding wheels, rotary centre, set of centers, set of workpiece drivers, set of throat gauges, lamp, 2 tool cabinets, tailstock with fine adjustment, oil mist extractor, spindle nose for collets. Achieves tight tolerances; typical applications: automotive, watchmaking, machine tool Tedpfxjxx U S As Ahujf

Condition: used, Year of construction: 1993, Technical details: rotary table diameter: 2x700 mm grinding height: 200 mm grinding head - power requirement: 15 kW max. dia. of grinding wheel: 400 mm grinding spindle speed: 1400-2800 stufenlos /continous U/min automatic feeds: 0,001-0,02 weight of tools max.: 650 kg table speed: 5-10 m/min rotary table revolutions per minute : 5-10 stufenlos U/min rotary table: Querbewg. 0,2...10 m/min total power requirement: 49 kW weight of the machine ca.: ca. 12,0 t dimension machine xH: 6,0x3,0x2,8 m dimensions electric cabinet LxWxH: 2,0x0,55x2,2 m ROTARY TABLE SURFACE GRINDING MACHINE - 2 magnetic rotary tables each Ø=700mm - diamond roller dressing device - without coolant unit Todeu Ngp Nspfx Ahujf i.D. *

Year of construction: 2005, operating hours: 22,640 h, condition: ready for operation (used), Control Unit Brand FANUC Model 21i-TB This 4-axis STUDER S33 cylindrical grinding machine was manufactured in 2005. It features a dynamic balancing unit, Marposs push button insert, and includes 2 CBN grinding discs. The machine also comes with approximately 20 internal grinding mandrels and 3 collets. Consider the opportunity to buy this STUDER S33 cylindrical grinding machine. Contact us for more information about this machine. Tedoxwzzzjpfx Ahusf Application Types Grinding

Condition: used, Year of construction: 2006, grinding diameter - cylindrical max. 650 mm grinding diameter - internal max. 600 mm control Siemens Sinumerik 840 D internal grinding depth max. 600 mm External grinding length max. 600 mm workpiece length - max. 380 mm turning speed range - stepless 1-795 U/min Workpiece spindle unit (U/B1/L adjustment): -Travel (U axis) 300 mm -Swivel angle (B1 axis) -1°/+12° -Speed range (infinitely variable) 1-795 rpm Todpfx Asw Rf Tvjhusf -Setup speed (tapping) 10 rpm -Spindle head size A 8 according to DIN 55026 -Through bore 58.5 mm -Workpiece diameter max. 830 mm -Workpiece length max. 600 mm -Load capacity at spindle head max. 6100 N Internal grinding device (Z1/X1/B2): -Travel (Z1 axis) 800 mm -Travel (X1 axis) 150 mm -Swivel angle (B2 axis) 270° -Drive power of internal grinding spindles (infinitely variable) 7.5 kW -Grinding block mounting bore (diameter) 100 mm -Grinding block mounting length (diameter) 100 mm -Grinding diameter max. 600 mm -Grinding depth max. 860 mm -Manual longitudinal adjustment of internal grinding axis on table 530 mm External and surface grinding device (Z2/X2): -Travel (Z2 axis) 800 mm -Travel (X2 axis) 470 mm -Drive power of external grinding spindles 5.5 kW -Mounting bore grinding block Ø 120 mm -Grinding diameter max. 650 mm -Grinding length max. 600 mm -Grinding wheel diameter max. 500 mm Equipment/accessories: -Various grinding spindles -Various flanges/grinding wheel holders -Various clamping jaws -Coolant system -Oil mist filter -Cooler -Technical documentation

Condition: used, Year of construction: 1994, Technical details: grinding diameter: 300 mm grinding length: 600 mm centre height: 190 mm z-axis: 865 mm x-axis: 250 mm clamping length: 1000 mm peripheral speed: 45 m/sec grinding slide swivable +/-: 8 ° grinding wheel width x diameter: 80 x 508 mm work piece spindle speed: 1 - 800 U/min weight of the machine ca.: 5 t Machine with SIemens 840 C control Tjdpfx Aevgbzdjhuof - coolant device - Marposs measuring device *

Condition: ready for operation (used), Year of construction: 2006, functionality: fully functional, machine/vehicle number: 2352, center height: 200 mm, grinding length: 500 mm, grinding diameter: 55 mm, rotational speed (max.): 5,970 rpm, controller model: Siemens Sinumerik 840-D, TECHNICAL DETAILS Grinding diameter: 5–55 mm Grinding length: 500 mm Workpiece diameter: 5–55 mm Workpiece length: max. 500 mm Grinding wheel arrangement: right, 30° inclined Grinding wheel dimensions: 600 x 30 x 203.2 mm Drive power: 7 kW X/Z-axis drive: ball screw Travel speed: 0.01 – 10,000 mm/min Resolution: 1 µm Workpiece spindle runout: < 1 µm Spindle speed max.: 5,970 rpm Workpiece changing system: Fanuc robot Control system: Siemens Sinumerik 840-D MACHINE DETAILS Total power requirement: 44 kW Centre height: 200 mm Machine weight: 7,000 kg EQUIPMENT Tailstock Tsdpexvxl Iefx Ahuof Longitudinal adjustment: manual Rotating centre: Junker standard, diameter 75 mm Clamping pressure: adjustable via hydraulic system Tailstock dimensions: diameter 100 mm × 430 mm

Condition: used, KELLENBERGER KEL-VARIA 2RU 225/1500 is a CNC cylindrical grinder engineered for precision, high accuracy and reliability. Capacities: centre height 225 mm, distance 1500 mm, max grinding Ø 432 mm, workpiece weight 150 kg; wheels L 400×63×127, R 500×80×127. Wheel speeds 1000–2150 rpm (45 m/s); work spindle 8–800 rpm, taper 5 CM, permitted load 160 Nm. Tailstock taper 4 CM, stroke 50 mm, pressure 200–700 N; supply 3×400 V 50 Hz. Options: KEL‑ASSIST 100, MOVOMATIC, KEL‑SET, MOVOMATIC C25, KEL‑BALANCE, coolant through spindle, paper filtration, 400 mm magnetic chuck, dressing, swivel diamond holder. Enables tight tolerances; sectors: automotive, watchmaking, machine tools, aerospace, medical. Todpfoxx U Hajx Ahujf

Condition: used, Year of construction: 1994, Technical details: grinding diameter: 198 mm grinding length: 200 mm z-axis: längs:240 mm x-axis: quer: 340 mm control: Tschudin CNC E 9034B grinding wheel diameter: 500 mm centre height: 100 mm Distance between centres: 300 mm max. workpiece weight between centres: 100 kg interface: RS 232 total power requirement: 16 kVA weight of the machine ca.: 4,5 t space requirement of the machine approx.: L:3,1xT:3,2xH:2,0 m Plunge type grinding automatic technical specifications: - grinding spindle tool intake: 203,2mm - grinding spindle not swiveling - workpiece spindle swivelling : +30° to -90° - tailstock collet cone = MK 3 - control: ISO - and graphically programing equipment: - electronical balancing device : AB 100 T.K. - grindig wheel changing aid - grinding disc dressing device (also for grinding forms programable) Tedpfx Aou Ng A Nehuof - cooling system with paper filtering system - Measuring device (out of function, integrated measuring control not connected) *

Year of construction: 2022, operating hours: 7,315 h, condition: used, machine/vehicle number: 100644, Max. grinding wheel diameter: approx. Ø 915 mm, max. workpiece diameter: approx. Ø 440 mm, max. workpiece weight: approx. 250 kg, max. grinding wheel speed: approx. 80 m/s, operating pressure: approx. 6 bar, control system, manufacturer: DANOBAT/SIEMENS/MARPOS, type: Sinumerik/P7, 1 automated workpiece removal station JOVI 1113B, year of manufacture: 2022, net weight: approx. 300 kg, 1 air filter unit IFS M 1600, year of manufacture: 2022, serial no.: 567663, net weight: approx. 85 kg, connected load: 380-460 V, 50/60 Hz, 0.7 kW, 1.5-2.1 A, 1 hydraulic unit REXROTH Depósito HE-16120, 1 coolant filtration unit MICRONFILTER Easy 250/KMT350, year of manufacture: 2022, serial no.: 0201, tank capacity: approx. 2,300 l, connected load: 400 V/50 Hz, 2.44 kW, 1 immersion cooler HASCH MCS-120ST-05AOP6R7S7UZ1-3405C, year of manufacture: 2022, serial no.: 1003220300954, net weight: approx. 206 kg, 1 magnetic separator MICRONFILTER KMT350, serial no.: 0211, 1 tool loading unit, DANOBAT rotary table lift, year of manufacture: 2022, serial no.: 3130490901, net weight: approx. 350 kg, max. payload: approx. 360 kg Tedpfx Ahjx Aklajusf

Condition: used, Year of construction: 1982, Technical details: grinding diameter: 600 mm grinding length: 3000 mm centre height: 315 mm workpiece weight max.: 3000 kg work piece spindle speed: 8 - 120 U/min grinding wheel motor: 25 kW grinding wheel speed: 45 m/sec grinding wheel width x diameter: 750 x 80 mm table speeds: 30 - 4500 mm/min feeds of grinding head: 0 - 5 mm/min table swivelabel +/-: 7,5 ° total power requirement: 55 kVA weight of the machine ca.: 18 t dimensions of the machine ca.: 11,5 x 4 x 2,2 m - Internal grinding device Tedpfxjvb Dl Uo Ahuof - taper grinding up to 10,1° based on diameter - automatic grinding cycle - grinding wheels and flanges - dressing device - coolant attachment - dust exhauster, various steady rests *

Condition: used, STUDER S41 is a CNC cylindrical grinder engineered for precision, high accuracy and reliability. Capacities: centre height 275 mm, distance between centres 1000 mm, max workpiece Ø 550 mm, workpiece height 1000 mm, Z 1150 mm, X 350 mm, workpiece weight 250 kg. Specs: grinding wheel Ø500×100 mm, peripheral speed 50/80 m/s, spindle speeds 0–4500 rpm, wheel head swivel -45/+225°, workpiece spindle motor 15 kW, 3x400 V 50 Hz, air 5 bar, tailstock stroke 60 mm (Ø 60 mm), machine weight ≈9000 kg. Accessories: high‑res C‑axis, B1+B2 axes, coolant system, internal grinding attachment, 2 spindles, lamp, status light, PC system, electronic handheld control, foot pedal. Achieves tight tolerances; typical in automotive, aerospace, toolmaking, medical and watchmaking. Todsxx U Dfjpfx Ahuef

Year of construction: 2023, operating hours: 1,376 h, condition: used, machine/vehicle number: 180073, Swivel range: approx. 200 mm, machining length travel: approx. 100 mm, number of axes: 3 axes (X/Y/Z), SIEMENS Sinumerik control, IFS IFMC 1800 air filter unit, year of manufacture: 2021, serial no.: 565760-02, HYFRA E-Chilly 5-400V-S cooling unit, year of manufacture: 2022, serial no.: 10129303PC01240522, cooling capacity: approx. 5,480 m³/32° Celsius, LEHMANN UMT KSS0119 hydraulic unit, year of manufacture: 2022, net weight: approx. 610 kg, comprising: 1 HYFRA TRK-Chilly-45-EF-S cooling unit, year of manufacture: 2022, serial no.: 10132616PC01290722, 1 LEHMANN UMT FB100 chip conveyor, year of manufacture: 2022, serial no.: AUF007093-1, net weight: approx. 80 kg, 1 LEHMANN UMT VMA 100S GM WA magnetic unit, year of manufacture: 2022, serial no.: AUF007093-1, net weight: approx. 60 kg, 1 JOTKEL two-door steel cabinet, contents: various consumables. Tsdpfjx Akkpex Ahujf