Used Precision Universal Grinding Machine for sale (67,248)

Condition: used, Technical details: swing diameter: 200 mm centre distance: 450 mm cross travel: 245 mm longitudinal feed: 830 mm table speed: 0,05-4,5 stufenlos m/min revolution per minute: Schleifspindel 1780, 2050 U/min revolution per minute: Werkstückspindel 50-500 U/min dimensions of grinding wheel: 350x32x127 mm Table dimensions: 2200x280 mm table swivelling to both sides: 9°vor+10°zurück Grad total power requirement: 6,0 kW weight of the machine ca.: 2,2 t dimensions of machine: 2,2x2,05x1,6 m Universal Center Grinding Machine without internal grinding device! - for precision grinding of outer, inner such as cone surfaces - feed of grinding headstock via hydr. or manual possible - table feed hydraulic stepless - grinding spindle swivelable with 60 degrees - workpiece headstock 90 degress swiveable with tapper MK4 - tailstock tapper MK 3 equipment: - dressing device/extruder - coolant tank incl. pump and supply i.D. * Crsdpfx Apju Ng Dgoteg

Condition: good (used), Year of construction: 1984, Used TOS KAMENICEK model BUC63A x 3000 Universal cylindrical grinding machine. YEAR OF MANUFACTURE: 1984. MACHINE FORMERLY INSTALLED AT ROLLS ROYCE PLC IN DERBY UK. IMMEDIATELY FOR SALE AND NOW LOCATED IN BELGUIM WHERE IT CAN BE INSPECTED. SPECIFICATION Max Swing 630 mm Distance between centres 3000 mm Workhead swivel – towards wheelhead only 90 deg. mm Work spindle bored taper No. 6 M.T. Length of stroke of tailstock barrel 70 mm Cjdpfx Apjh U Rznjtjrg Tailstock barrel taper No. 6 M.T. Spindle nose clamping Din 55021 Swivelling of wheelhead + 30 deg – 10 deg Length of adjustment by re-circulating ball screw 290 mm Additional length of adjustment 250 mm Length of rapid feed 90 mm Length of infeed setting per each rev. of handwheel, measured on work diameter 0.5 mm Grinding wheel dia. X width X bore 750 x 80 x 305 mm Min. dia. of worn grinding wheel 570 mm Max. face width of grinding wheel 125 mm Rate of table traverse – steplessly variable 0.5-0.6 m/min Table traverse per 1 rev of handwheel 8 mm Swivelling of table +/- 5 deg. Max. permissible weight of work between centres 2500 kg Max. permissible weight of workpiece in chuck with overhang. (including weight of chuck) 150 kg Wheel spindle speeds (2) 840,970 rpm Grinding wheel surface speed 33 m/sec Work spindle speeds – int. var. in 2 ranges 8-50, 50-315 rpm Drive – total power required rated 31 kva Output of workhead motor 3 kw Output of wheelhead motor Electrics 15 kw 415V ,3Ph,50Hz Equipped with:- Additional wheel flanges, coolant system with clarifier and splash guards. FEATURES AND EQUIPMENT – Swivel Round Internal Grinding Attachment

Condition: used, Surface grinding machine, precision surface grinding machine BRAND (Switzerland) Type Mini 500 Machine No.: 505/86 Year of manufacture: 1986 Electro-magnetic clamping table 450 x 200 mm Grinding length 500 mm Grinding width 240 mm Cross travel 220 mm Table longitudinal travel 550 mm Distance between spindle center and magnet max. 350 mm Grinding wheel diameter 225 mm Grinding wheel width max. 25 mm Grinding wheel bore 50.8 mm Table longitudinal feed 0.5-24 m/min, stepless Table cross feed, pulse 0.05-30 mm Cross feed rate 10 - 1000 mm/min Vertical feed 0.001 - 0.05 mm Vertical feed rate 600 mm/min Grinding wheel speed 2820 rpm Grinding wheel speed 33 m/s Motor power, grinding spindle 2.2 kW Motor power, hydraulics 1.1 kW Mains connection 400 V, 50 Hz, 9.5 kVA - automatic depth feed, vertical feed - mechanical handwheels for axis movements - hydraulic table longitudinal movement - electromagnetic plate WAGNER 450 x 200 mm, height 73 mm - central lubrication system - band filter system with coolant tank and pump, adjacent, L x W x H = 1300 x 500 x 650 mm - 2 additional grinding wheel arbors for grinding wheels with 50.8 mm inner diameter - 1 balancing mandrel and 1 grinding wheel puller - adjacent hydraulic unit, L x W x H = 700 x 300 x 750 mm Cjdpfx Apsd Nrqfstjrg Space requirement L x W x H 2000 x 1400 x 2250 mm Weight approx. 1600 kg Good condition

Condition: used, Year of construction: 1990, grinding diameter 360 mm Crjdpfx Aexbh Eboptsg grinding length 1000 mm centre height 180 mm max. workpiece weight between centres 250 kg Maschine mit sehr wenigen Betriebsstunden nach Überholung beim Karstens Fachbetrieb. Zustellsteuerung Jetter Digitalanzeige Innenschleifvorrichtung Reitstock mit Zylindrizitätsfeinverstellung Hydraulische Reitstockpinole Etc... Luftkissenschnellverstellung Schleifspindelstock

Condition: excellent (used), Year of construction: 2001, Description to follow! Cedezd E Tzspfx Aptorg

Condition: used, Year of construction: 1982, Technical details: grinding diameter: 350 mm grinding length: 1000 mm centre height: 225 mm grinding length: max. 1600 mm centre distance: 1540 mm spindle bore: 38 mm max. swivability: 90 ° weight of the machine ca.: 6,0 t dimension machine xH: 4,4 x 2,45 x 2,3 mm Crjdpfow Rktzsx Aptog Machine with CNC package and DFU connection Multi-range measuring head for interrupted surface Tailstock with cylinder error correction Final balance balancing device *

Condition: ready for operation (used), Weight: 2.2t, including documentation. Cjdemqly Uopfx Aptsrg

Condition: excellent (used), with internal grinding attachment Crodsiu E Trjpfx Aptsg Center height 125 mm Distance between centers 600 mm Grinding wheel 400 x 40 x 127 mm Misc.accessories MARCELS MASCHINEN AG

Condition: used, Year of construction: 1995, grinding diameter 350 mm grinding length 1000 mm centre height 175 mm Crodpfx Apjyatx Soteg Teilüberholte Maschine mit Messprotokoll nach Neumaschinentoleranz NEUE Steuerung Eckelmann ENC mit BEMA Schleifsoftware KEL-ASSIST für Kelco 90 numerisch gesteuerte B-Achse Innnschleifrinrichtung Dia 80mm Schleifscheibe links Durchmesser 400mm Schleifscheibe rechts Durchmesser 300mm Innenschleifspindel HJN 828 hydraulischer Reitstock Mikroverstellung KEL SET Messsystem

Condition: good (used), Year of construction: 2013, grinding diameter 390 mm Csdpfx Aow Inr Nsptsrg grinding length 650 mm centre height 200 mm control Siemens 840D total power requirement 46 kW weight of the machine ca. 6 t dimensions of the machine ca. 3x3x2,4 m Universal cylindrical grinding – Type WUG21 (W27) Grinding length 650 mm EMAG Weiss stands for high-end technology in universal cylindrical grinding between centres. With its CNC-controlled WUG 21 machines, EMAG Weiss offers the right solution for virtually every user. --> Technical data Max. grinding length: 650 mm --> Centre height: 200 mm --> External grinding diameter: 1 – 390 mm --> Max. weight flying MK4: 100 kg --> Max. workpiece weight between centres: 250 kg --> Feed: --> X-axis travel: 480 mm --> Z-axis travel: 1.150 mm --> Workpiece headstock --> Tailstock --> Grinding spindle headstock --> Coolant device, manufacturer HYFRA, --> Belt filter, manufacturer Knoll, type KF 200 - year of manufacture 2012, --> Oil mist filter, manufacturer Cobaron Here are a few specifications for the machine: - Grinding length / max. workpiece length: 650 mm - Max. workpiece diameter: 400 mm (center-to-center distance: 200 mm) - Workpiece headstock: MK4, speed up to 600 rpm, continuously adjustable - Hydraulic NC tailstock with 150 mm stroke, MK4 - 2 external grinding spindles—1 wheel on the left, 1 wheel on the right—B- axis infinitely adjustable - Grinding wheel peripheral speed: 50 m/s - Grinding spindle motors: 7.5 kW each, toothed belt drive - Machine dimensions (without external peripherals): Width 4130 x Depth 2400 x Height 2300 mm - No rotating dressing device for CBN grinding wheels; only a holder for a stationary dressing tile

Condition: used, Year of construction: 1980, Technical details: Cedpfx Aowy Ri Nepterg 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 *

Condition: good (used), grinding diameter 450 mm grinding length 600 mm centre height 140 mm workpiece dia. 280 mm Crjdpjxcblqsfx Aptsg number of turns of spindle head 63 - 400 U/min grinding wheel speeds 20-35 m/s dimensions of the machine ca. 2,4 x 1,9 x 2,1 m

Condition: excellent (used), with internal grinding attachment Center height 125 mm Codpfoy H Dq Hox Aptorg Distance between centers 1000 mm Table size 1650 x 145 mm Grinding wheel 400 x 50 x 127 mm Grinding wheel speeds 1'500 - 2'200 rpm Grinding head turnable 270° Grinding wheel 225 x 20 x 76.2 mm Misc. accessories MARCELS MASCHINEN AG

Condition: as good as new (ex-display), Year of construction: 2025, Offered is a CNC controled universal cylindrical grinding machine EMAG Weiss W 11 CNC. The machine is suitable for external-interna- face and cylindrical grinding. The W 11 CNC cylindrical grinding machine is perfect for one-offs- / prototype- and serial production. This cylindrical grinding machine is also used for sample production in the field of training and maintenance. CONTROL Eckelmann TECHNICAL DATA Workpiece length: max. 1.500 mm Center height: 200 mm | Option 320 mm Workpiece weight: 250 kg Workhead: MK 4 | Option MK5 / MK6 Tailstock: MK 4 TOOL CARRIER Single wheel straight / incliend, but also possible 2 wheels on B-axis combined with internal grinding spindle. Price, delivery time and equipment of the machine according to agreement. Crjder Ey Huopfx Apteg

Condition: used, Year of construction: 2002, grinding diameter 350 mm grinding length 1000 mm centre height 175 mm dimensions of the machine ca. 3,6/3,5 m Photos of identical machine with centre height 225mm Base: Kellenberger Kel-Varia UR175-1000 Kelco 120 Grinding head UR with T1-T2-T3 Basic equipment: -T1 500mm grinding disc diameter -T2 400mm grinding wheel diameter -Infinitely variable, high-resolution axis -Marposs measuring device for tool measurement -Active longitudinal positioning -GAP on T1 and T2 from ELASO contactless integrated in the control interface Semi-automatic balancing from ELASO integrated into the control interface -Tailstock with manual retraction -MK5 workpiece headstock with short taper DIN 55026 Belt-driven internal grinding device Options at an extra charge: - New high-precision workhead with torque drive - Internal grinding device for high-frequency spindles diameter 120mm -HF internal grinding spindle Fischer MFM-1224/42/31 D-21 -HF spindle with HSK holder 24,000 rpm with integrated GAP sensor. (delivery time) -CNC-controlled C-axis non-circular grinding -hydrostatic threaded spindle in x -new hydrostatic unit with only 1 pump and pressure accumulator thus better energy efficiency. -monitoring of the water content in the hydrostatic system -Suction system Further options available on request Mechanical overhaul: -Complete machine overhauled according to Kellenberger measurement protocol -New service-friendly cab -repainting Electrical overhaul: -New modern CNC CIRCULAR GRINDING MACHINE control with BEMA rough grinding surface -New control cabinet -New drive technology -Replacement of all electrical cables Berus pressure switches etc. -New absolute glass scales in x and z -New absolute rotary encoder (for B-axis) Control system: The grinding software consists of a basic licence and various options that are possible depending depending on the equipment of the machine. Basic software - External and internal pendulum grinding - External and internal plunge-cut grinding - External and internal pendulum grinding - External and internal plunge-cut grinding - External and internal taper pendulum grinding - External and internal radius grinding, radius dressed on disc - Semi-automatic pendulum grinding - Workpiece zeroing - Grinding wheel zeroing - Measuring the dressing diamonds - 2 moulding diamonds - 1 shaped diamond or dressing roll (dressing roll required) - Moulding roller (dressing roller required) - 3 Flat dresser - Corrections - Z-position measurement (probe required) - GAP probing (grinding device required) OPTIONS at an extra charge: Software profile plunge-cut grinding: - External and internal profile plunge-cut grinding with profile disc Profile grinding software: - External and internal profile grinding with straight disc Software thread grinding: - Single and multi-start external and internal thread grinding with thread on the disc disc Dressing. Dressing of single and multi-groove discs. Flank angle freely selectable. Trapezoidal thread grinding software: - Additional dressing of trapezoidal threads possible External and internal non-circular plunge-cut grinding: - External and internal non-circular plunge-cut grinding Non-circular grinding software: A prerequisite for non-circular grinding is that the workpiece axis is equipped with a high-resolution rotary encoder so th... Credpsuxfucefx Aptog

Condition: used, Year of construction: 2002, grinding diameter 450 mm grinding length 1500 mm centre height 225 mm Control FAGOR EQUIPEMENT - T1: grinding wheel diameter 500 mm - T2: grinding wheel diameter 400 mm - T6: HF Fischer spindle MFV or MFZ 1224/1242/1260 - T7: HF Fischer spindle MFV or MFZ 1224/1242/1260 - Marposs tool measurement - active longitudinal positioning - Elaso GAP-control on T1 and T2 contactless integrated in the control surface - Elaso GAP internal grinding with fluid sensor for T6 and T7 - semi-automatic balancing by Elaso integrated in the control surface for T1/T2 - tailstock hydraulic with fine adjustment +/- 150 microns - dresser on workpiece spindle side table mounted - dresser on tailstock side table mounted - dresser on upper table - new service- and userfriendly housing SPECIAL EQUPEMENT: Workhead with direct drive - strongly recommended for non-circular grinding - workpiece weight flying max. 75kg - workpiece weight between centres 150kg - water-cooled B-axis with direct drive - center height 225 mm - extremely torsionally stiff Cjdouxfu Nopfx Aptsrg - highly accurate positioning - resolution ° - water-cooled Hydrostatic ball screw - x-axis - wear-free, as there is no contact during operation - no loss of precision, even during long-term use at full load and maximum speed - no friction at low speeds - no friction force backlash when the direction of rotation changes - translates even the smallest rotational movements - no stick-slip effect even at low speeds - no fluctuations in frictional torque due to ball circulation - higher axial stiffness compared to ball screws - significant improvement in damping, resulting in better workpiece surface finish and tool life - no oscillations due to ball circulation - also suitable for high speeds and accelerations - cost-effective alternative to the linear motor with greater precision and significantly lower heat generation - significantly less power dissipation and, as a result, no problems with swarf on permanent magnets New hydraulic unit - optimized temperature control (chiller) - Energy-saving Only one pump controlled by VFD - Pressure monitoring - monitoring of the hydrostatic oil for water content. (Damage to the bellows is recognised and detected prematurely) -fine adjustment +/- 150 microns Paper belt filter 375l – alternative 480l Grinding mist extraction system – emulsion MECHANICAL OVERHAUL -complete machine according to Kellenberger protocoll -new painting ELECTRICAL OVERHAUL - new modern Fagor CNC with BEMA HMI - new electric cabinet - new digital drive technology - replacement of all electrical cables, switches etc. - new absolute external scales in x- and z-axis - new absolute encoder (B-axis) Grinding software BEMA-Standard: - workpiece zeroing - grinding wheel zeroing - dressing diamond measuring - corrections - external and internal surface grinding - external and internal angle grinding (turning of the b-axis, dressing with straight wheel) - external and internal radius grinding (radius dressed on wheel) - semi-automatic traverse grinding - workpiece zeroing - 2 dressing diamonds - 1 dressing blade - dressing roll - 3 flat dresser - corrections - Z-position measurement - GAP control Optional grinding cycles at no extra charge: Profile plunge grinding: - external and internal profile plunge grinding with profile wheel Pr...

Condition: used, Technical details: grinding length: 300 mm 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 Credezaunzepfx Aptjg 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: as good as new (ex-display), Year of construction: 2025, Offered is a external cylindrical grinding machine EMAG WPG 7 - external cylindrical grinding at the highest level and on the smallest footprint. Footprint of the WPG 7 is only 1,800 x 2,400 mm. The machine is perfect for machining small shafts or pinions. The WPG 7 can be loaded manually as well as by automated solutions (such as chain conveyors and linear gantry). CONTROL Fanuc 0i TECHNICAL DATA Workpiece length: max. 250 mm grinding Ø: max. 80 mm Center height: 100 mm Center length: 380 mm Workpiece weight: max. 30kg Grinding wheel Ø: max. 500x 80 mm Price, delivery time and equipment of the machine according to agreement. Csdpfx Aotlrkbsptjrg

Condition: reconditioned (used), Year of construction: 1985, functionality: fully functional, Completely overhauled by the original manufacturer's staff. Cedpfx Apoychhtotsrg Max. grinding diameter: 250 mm Grindable length: 750 mm Accessories: - Auxiliary hydraulic unit and control cabinet - Tailstock - Work spindle - Wet grinding attachment - Internal grinding unit - Balancing mandrel - Further accessories available upon request The machine is currently powered up and located in Hungary. An inspection is possible by appointment. The overhaul warranty is 6 months within Hungary.

Condition: used, grinding diameter 250,350,450 mm grinding length 1000 mm centre height 125,175,225 mm grinding wheel diameter 400 mm grinding wheel width 50 mm bore 127 mm MK5 work piece spindle speed 20-400 U/min grinding head swivelling 360 ° grinding spindle head - swivable 180 + - ° grinding spindle speed 1500,1700,2200 U/min 0,001-0,030 mm/Ø 0-0,95 mm/Ø ±8 ° longitudinal feed of the table 1300 mm table speeds 0,02-6 m/min 130 kg 130 inkl. Spannugkg kg 70 mm total power requirement 6,5 kW weight of the machine ca. 2,5 t dimensions of the machine ca. 4,2 x 2,0 m As the world’s leading company in Kellenberger overhaul and retrofit we are not Codpfx Apst Ii Nuotjrg only able to deliver machines in a quality similar to a new machine and with warranty, but we can also offer you the service for your machines. Geometrically overhauled with new paint and original electrics. Foto of a 600U which we already have delivered. -Digital display in 2 axes. Resolution of x-Achse 0,5my Options: -Encoder with digital display in workpiece spindle head -Encoder with digital display in grinding spindle head (Height adjustment with spindle not possible) -New stable internal grinding diameter 80mm oder 100mm with height-adjustment. -Increase the center heigh to max. 225mm -Speed control of the grinding spindle Including:: -Adjustment tool -Draw tube for chucks other accessories on reqeust Die Werkzeugmaschine entspricht zum derzeitigen Zeitpunkt nicht den grundlegenden Sicherheits- und Schutzanforderungen wie in der BetrSichV 2015 genannt. Eine Anhebung des erforderlichen Mindest-Schutzzieles ist mittels einer Gefährdungsbeurteilung nach BetrSichV zu ermitteln.

Condition: used, grinding diameter 360 mm grinding length 1000 mm centre height 260 mm grinding wheel dia. x width 500x80 mm Csdpfx Aeyqv Udoptsrg The tech. Data are manufacturer or operator information and therefore non- binding. We reserve the right to prior sale; Our terms and conditions of sale apply exclusively. About us More than 400 of our own machines in stock Over 15,000 m² of storage space, 70 t crane capacity More than 10,000 items and accessories for your workshop If you are interested in selling machines, production lines, or your business, please contact us. You can find further offers on our website. Tours are possible by appointment. We look forward to your visit. Your Markus Hirsch Team

Year of construction: 1979, condition: refurbished (used), functionality: fully functional, TECHNICAL DETAILS Maximum height: 125 mm + 50 mm height adjustment Distance between centers: 1,000 mm Grinding wheel › Diameter: 400 mm › Width: 50 mm › Bore: 127.0 mm Angle adjustment: 270° Workpiece spindle head: 20 - 400 rpm Spindle taper: 5 MT Tailstock taper: 3 MT Table angle adjustment: 8° Table speed: continuously variable up to 6.0 m/min Internal grinding spindle with 60,000 rpm External grinding wheel motor: 4.0 kW Workpiece spindle motor: 1.5 kW Machine weight: 3,100 kg Overall machine dimensions: 2,860 × 1,680 × 1,670 mm (L × W × H) EQUIPMENT & SCOPE OF DELIVERY • Machine completely refurbished • New control cabinet & new wiring diagram • New motor & frequency inverter for the working head • 2-axis DRO • Coolant tank with paper filter Crjdpsk H Hp Nsfx Aptjg • Geometry manufactured according to the Kellenberger protocol • Internal grinding spindle • Numerous accessories Please refer to the test report for the machine in the appendix below.

Condition: used, grinding diameter 350 mm grinding length 1500 mm centre height 175 mm weight of the machine ca. 3 t High-End Kellenberger 1500U Ideal for spindle producer or overhauler -BEMA Internal grinding device with separate, cooled motor. Grinding spindle and internal grinding spindle motor electrically interlocked! Internal grinding spindle can only be switched on when it is in position. A quantum leap in safety -Infinitely variable grinding spindle speed 1000-1500 rpm -Infinitely variable internal grinding spindle speed 0-100%. -Digital display of grinding spindle speeds Credpfx Apst Ii Rretjg -Swivelling angle display top table -swivel angle display grinding headstock -Marposs gaper sensor for external grinding only -fluid gating sensor Marposs internal grinding -Center height up to 250mm possible Machine is already delivered. Identical machine can be built with additional with additional options. Die Werkzeugmaschine entspricht zum derzeitigen Zeitpunkt nicht den grundlegenden Sicherheits- und Schutzanforderungen wie in der BetrSichV 2015 genannt. Eine Anhebung des erforderlichen Mindest-Schutzzieles ist mittels einer Gefährdungsbeurteilung nach BetrSichV zu ermitteln.

Condition: used, grinding diameter 450 mm grinding length 1000 mm centre height 225 mm Fotos von bereits gelieferten Maschinen. Mechanische Überholung: -komplette Maschine nach Kellenberger Messprotokoll überholt -Neue servicefreundliche Kabine -Neulackierung Elektrische Überholung: -FANUC Steuerung mit BLUE-SOLUTION -Neu aufgebauter Schaltschrank -Neue Antriebstechnik Credpfx Apjzkvucotog -Austausch sämtlicher elektrischer Leitungen Berus Druckschalter etc. -Neue Absolut-Glasmaßstäbe in x- und z -Neuer Absolut Drehgeber (Bei-B-Achse) Fotos von bereits gelieferter Maschine mit anderen Optionen. Schleikopfvariante UR/RS: -Schleifscheibenanordnung für Aussen -und für Schrägeinstichschleifen hintereinander! -Dadurch jeweils 400mm Scheibendurchmesser! -Dadurch wesentlich geringere Kollisionsgefahr -Einfacheres programmieren -Schleifscheibenausrüstung jeweils 400x63x127mm -Einrichtung zum Betrieb einer HF-Spindel -Spindel optional gegen Aufpreis -B-Achse CNC gesteuert zum Aussen-Plan- und Innenschleifen in einer Aufspannung. Schwenkbereich +10°/-270° -C-Achse zum Polygonschleifen -Unterteil fest -Schleifkopfmotor 10,0 KW -Reitstock -Marposs Messsystem zur Schleifscheibenvermessung. -Längspositionierung Marposs

Condition: used, Year of construction: 2017, Technical details: grinding diameter: 280/320 mm grinding length: 750 mm centre height: 170 mm weight of the machine ca.: 22,5 t Crodpettxg Ssfx Aptjg dimensions of the machine ca.: 4,7 x 3,65 x 3,0 m