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Model 312 Maintenance Guide

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Model 312 Maintenance Guide

The Mereen-Johnson Model 312-DC is a fixed arbor rip saw built for reliable, high-production straight-line ripping. Like every precision rip saw, it delivers its best yield, cut quality, and uptime when it’s on a disciplined preventive maintenance program. Effective maintenance on the Model 312 spans the anti-kickback safety fingers, the oil mist lubrication system, the feed chains and dip cams, the press roll and bed plate relationship, the arbor and bearings, and the feed drive.

This guide covers the complete Model 312 maintenance program organized by service interval, plus the key procedures every maintenance team should understand. For full step-by-step disassembly and rebuild procedures, the complete manual is available as a download.

Safety first: Always disconnect the main power supply before servicing the machine. Clean anti-kickback fingers daily with air only — never oil them.

For the complete reference, view the full Model 312 Maintenance Guide PDF.

Daily Maintenance

Daily maintenance focuses on cleanliness, lubrication levels, and the anti-kickback safety system. These checks take 15–20 minutes and prevent the majority of wear and downtime issues.

  • Fill all oil cups with 10W non-detergent oil
  • Check anti-kickback fingers for wear, stuck or bent fingers, and free swinging — fingers must return to their starting position. Clean with air only; do not oil
  • Walk around the machine to inspect for developing problems
  • Blow all debris off the machine with compressed air
  • Clean the arbor shaft with solvent and apply a light film of 10W non-detergent oil
  • Check oil mist nozzles for proper aim, oil output, and any damage

Monthly Maintenance

  • Check arbor shaft run-out and bearing integrity — run-out should be less than .002″
  • Check arbor sleeves for damage and excessive wear
  • Clean and flat-file all aluminum spacers
  • Check the #3 rubber-covered press roll and rubber feed slat inserts for wear
  • Check the press roll to bed plate relationship

Quarterly Maintenance

Four times a year, perform these deeper inspections and adjustments:

  • Check and adjust all air pressures as needed
  • Check Bijur mist oil units oil output quantity
  • Check feed drive chain sprocket condition and check for loose set screws
  • Check dip cams, feed sprockets, feed chains, and chainway for wear
  • Check and adjust the press roll housing gib and the arbor motor gibs
  • Check lube level in the feed drive gear box
  • Check press roll housing adjust screws and brass nuts for wear
  • Check the arbor motor hoist for wear (if equipped)
  • Tighten all electrical connections and inspect all electrical components

Hour-Based and Annual Maintenance

Every 400 Hours

  • Grease the entire machine — do not over-grease the arbor bearings

Annually

  • Check the gib screws (if equipped): Hold the set screw in place with an Allen wrench, loosen the jam nut, tighten the set screw just enough to feel it touch the gib, then hold that position and tighten the jam nut
  • Replace the oil mist filter group once a year

Anti-Kickback Finger Maintenance

The anti-kickback fingers are the Model 312’s primary operator protection against material kickback, and they require specific daily attention:

  • Clean daily with air only — never oil the fingers
  • Replace any worn kickback fingers. Test for sharpness using the cardboard strip provided in the back of the manual
  • Confirm free movement — fingers should always swing freely and return to their original position
  • Lower kickback finger positioning: 1.75″–2.00″ above the table top
  • Optional guide assembly positioning: between .03″ and .06″ below the table top
  • Dust collection at the kickback hood: 680 CFM, 4″ water gauge, 5000 FPM minimum velocity

For additional safety system background, see our general saw safety guide and fixed arbor safety features.

Oil Mist Generator System

The oil mist generator provides essential lubrication to the bottom chain vees and chain pins. Without proper oil mist, the feed chains, extended pins, and cams will wear excessively. Depending on age and configuration, the Model 312 may be equipped with a Bijur (Type Z), an Alemite (Type 3942-BC), or — on machines built prior to mid-2011 — an earlier oil mist unit. All function the same way.

Weekly Nozzle Verification Procedure

Check the position of the four spray nozzles weekly to confirm they’re spraying on the chain vees and pins. The feed chains must be running to check the nozzles — use extreme caution and have someone standing by the main power switch.

  1. With the feed chains running, hold a piece of white paper in front of each nozzle for 30 to 40 seconds
  2. After 40 seconds, there should be an oil spot the size of a quarter
  3. If there’s no stain, check the nozzles for obstructions — dust collects at the nozzle discharge fitting and should be removed during weekly cleaning

Oil Mist Maintenance

  • Check the oil level daily and refill the reservoir as required (fill to, but never above, the top of the Liquid Sight Gauge)
  • Use only clean oil of the type and viscosity recommended by the machine manufacturer
  • Never remove the filler plug when the unit is in operation
  • Check filters periodically and clean or replace as necessary
  • Drain accumulated water and impurities from the air reservoir as needed
  • Replace the filter group once a year (Alemite part #387295 for Alemite units)

For detailed lubricator service procedures, see our Alemite lubricator service guide.

Press Roll and Bed Plate Relationship

The relationship between the press rolls and bed plate is factory-preset and critical to cut quality. On the Model 312’s 3″ air-loaded press roll system, with the relationship preset for 1/8″ smooth material:

  • The press rolls yield (raise) 3/16″
  • The bed plate yields (raise) 1/16″

Press roll height adjustment: Use the press roll height adjustment bolts to reset the rolls from 1/8″ yield (smooth material) to 1/4″ yield (rough material).

Pressure adjustment:

  • Roll pressure: turn the air regulator up — 25–35 PSI is normal, with a maximum of 60 PSI. When resetting rolls from 1/8″ to 1/4″ for rough material, do not increase the pressure
  • Bed plate pressure: turn tension nut counterclockwise. Check four times a year to maintain .080″–.100″ clearance between the spring coils

Important: Never attempt to achieve more holddown pressure by lowering the press roll assembly. Doing so damages the press roll to bed plate relationship.

Spring-Loaded Press Rolls (Older Machines)

Machines with the older spring-loaded press roll system follow the same yield specs (3/16″ press roll, 1/16″ bed plate for 1/8″ smooth material). On these models, check the spring pressure on the press rolls every 90 days — the gap between spring coils should maintain 1/8″ of clearance. Compression of the urethane grommets from normal wear will eventually require readjustment of the vertical height adjustment nuts.

Feed Chain and Dip Cam Maintenance

  • Dip cams are designed to be switched left-to-right once when worn on one side. Before switching, remove the outside tie bar, bed plates, and inside tie bar. After the cams are worn a second time, install new cams.
  • Feed chains: Over time the chain pins wear on top. If the flat spot on the chain pin is 3/16″ or greater, replace or rebuild the feed chain (56 links).
  • Daily compressed-air cleaning dramatically reduces the sawdust buildup that accelerates feed chain and dip cam wear.

Contact Mereen-Johnson Customer Service to order new dip cams or feed chains.

Electronic Shear Pin (Current Sensor)

The Model 312 uses a current sensor as an electronic shear pin — it monitors normal current draw on the feed motor, and if current climbs above the set level, it trips out and shuts off the feed drive to protect the machine.

  • Trip delay potentiometer should be set full counterclockwise for no delay
  • Adjust the trip point clockwise until the red LED light goes out. Turning this adjustment up too far can cause severe damage to the feed drive system
  • Automatic reset: If the sensor trips, it resets itself automatically. Before restarting the feed, locate and correct the reason it tripped
  • VFD-equipped machines: The frequency controller has a built-in, factory-set current sensor

Caution: Disconnect all voltages before making connections to the current sensor.

Machines built prior to the “J” Model use this electronic shear pin system. Very old machines may use a mechanical shear pin, which is replaced by aligning the shear hub and bushings and installing a new pin flush with the bushing.

Feed Drive (Variable Frequency Drive)

If your Model 312 is equipped with a Variable Frequency Drive controlling feed bed speed, all drive parameters are factory set and should not require modification. For specific drive values, refer to the electrical schematic. Before changing any drive parameters, contact the Mereen-Johnson Service Representative at 612-302-3323.

Varimot Drive (Older Machines)

Machines built prior to the “J” Model may use a Varimot variable speed drive instead of a VFD. The Varimot consists of a motor with dovetail slide, drive disc, hollow shaft with friction ring, and torque compensator (lobe cams). Friction disc replacement, bearing regreasing (Shell Alvania or equivalent for needle bearings; Lubriplate GR-132 for cam lobes), and driving cone removal procedures are detailed in the downloadable manual. When regreasing, do not overfill the cavity — too much grease generates excessive heat.

Arbor Motor and Bearing Service

Model 312 arbor motor bearing replacement is a detailed procedure requiring a dead-blow hammer and careful bearing handling. Key points:

  • Hand-pack bearings 1/3 full with Molylube 126-EP grease or equivalent
  • Heat the front bearing inner race to approximately 120°F–140°F using a bearing core heater, oven, or light bulb to slide it onto the journal
  • Apply anti-seize compound to the arbor shaft before final assembly to ease future disassembly
  • If equipped with an arbor brake, remove the brake assembly before removing the arbor (mark air lines for reassembly)

The complete step-by-step disassembly and reassembly procedure (with numbered part references) is in the downloadable PDF. Given the precision required, arbor motor service is a good candidate for factory technician support.

Infeed and Outfeed Conveyor Setup

Proper conveyor integration directly affects cut quality on the Model 312.

Infeed conveyors should:

  • Run at the same speed as the rip saw feed bed (speed mismatches affect cut quality, jam the feed bed, double-feed, or kick boards to one side)
  • Be parallel with the direction of feed
  • Have at least the closest roller parallel to the saw arbor

Outfeed conveyors should:

  • Run no more than 10% faster than the saw’s feed bed
  • Accept material straight out of the saw
  • Be level with the saw’s outfeed

Infeed nip rolls should jump down as material passes under, raise off the material by the time the 2nd press roll touches it, run at the same speed as the feed bed, and be positioned parallel to the arbor and level with the infeed table.

Related Troubleshooting and Reference Guides

For complete coverage of your Model 312 fixed arbor rip saw, review these related resources:

Need Service or Replacement Parts?

The Model 312 is a precision machine, and some maintenance — particularly arbor motor bearing replacement, Varimot drive service, and current sensor adjustment — benefits from factory expertise. If you’re planning a major service event, training your maintenance team, or need exact-fit replacement parts (dip cams, feed chains, bearings, anti-kickback fingers), our factory team can help. Mereen-Johnson maintains the original manufacturing records and parts inventory for every Model 312 we’ve built.

Contact Mereen-Johnson service or call (612) 529-7791 to speak with a factory technician about your Model 312.