Magnetic drill maintenance: magnet base, cable and brushes

The advice is taken from Rotabroach's operating instructions for the Commando 40, the air-powered Eagle and the hydraulic Gator. Disconnect the power, compressed air or hydraulics before adjustment, servicing and maintenance.

Before each job

• Before you start, secure the machine to something solid with the RD4329 safety strap or by another safe method. Always do this, so that the machine cannot move freely if the magnet loses its grip
• Inspect the machine for damage that could affect its use, paying particular attention to the power cable. If the machine appears damaged, do not use it
• Check that there are no damaged or loose parts. Loose parts should be tightened
• Check that the magnet base is flat and undamaged. An uneven magnet base holds less securely and can injure the operator
• Keep the workplace and the machine free of swarf and dirt, especially the underside of the magnet base
• The machine must not be used if parts are missing or damaged
• If the machine has been dropped, examine it thoroughly for damage and check that it works before you continue drilling

Damage to the magnet base

Pits and other damage to the magnet base weaken the holding force. Any unevenness on the magnet base or the workpiece can be filed flush with the surface, but this must be done with great care. The guide Magnetic drill holding force explains more about what affects the grip.

Cable and power on the Commando 40

• Check the cable at regular intervals. If it is damaged, it must be repaired by an authorised Rotabroach service centre
• Do not pull the cable to unplug it, and keep it away from heat, oil and sharp edges
• The machine has 3 metres of 1.5 mm² three-core cable. With a 3 × 1.5 mm² extension cable, Rotabroach recommends a maximum of 3.5 metres at 110 V and 26 metres at 230 V. An undersized extension cable gives a weaker magnet and less motor power
• A high-sensitivity 30 mA residual current device improves electrical safety
• Do not use the magnetic drilling machine on the same structure while welding is in progress. The direct current can then go to earth through the magnet and cause irreparable damage

Carbon brushes, armature and gearbox

The carbon brushes should be checked for abnormal wear, at least once a week if the machine is used heavily. If they have worn down too far compared with their original length, they must be replaced, or the machine may be damaged. The contents list in the operating instructions includes a spare carbon brush, part number RD35612.

The armature should be checked at least once a month for visible damage to the armature itself and to the commutator, the part the brushes bear against. Some wear on the commutator over time is normal, but if there is abnormal damage, the part must be replaced.

The grease in the gearbox should be checked once a month to make sure that all moving parts are covered. The grease should be changed at least once a year.

The troubleshooting list points to the wear parts as follows:

• The motor hums, sparks heavily and lacks power: burnt armature or field, or worn-out carbon brushes
• The magnet works, but the motor does not: causes include carbon brushes that have stuck or are worn out
• The motor rattles: worn bearing at the bottom of the armature, worn gears or a lack of grease in the gearbox

Slide and bearing bracket

The slide should run smoothly and in a controlled way, without sideways play or vibration. Keep it that way by adjusting it at regular intervals:

• Run the slide all the way up, clean the brass strips and lubricate the wear surfaces with a little light machine oil
• Run the slide all the way down, centre it in the dovetail and loosen the screws
• Tighten the screws, starting with the middle ones, until you feel slight resistance. Run the slide up and down, and adjust until it moves freely without sideways movement
• Run the slide all the way up, loosen the bearing bracket slightly and tighten the screws finger-tight
• Place the machine on a steel plate, switch on the magnet and start the motor. If the bearing bracket swings, the spindle is not aligned. Adjust, tighten the screws and finally the bearing bracket

Lubrication and stiff feed

The Gator operating instructions ask you to lubricate the slide and the bearing in the spindle support regularly with a little light oil. Rotabroach states that annular cutter breakage is usually caused by poor clamping, a loose slide or a worn bearing in the spindle support.

If the feed is stiff, the guide may be overtightened or dry, or the guide, rack or rotation system may be dirty or damaged.

Eagle and Gator: air and hydraulics

The Eagle should have a filter and lubricator in the air line, no more than 5 metres from the machine. To get the most out of the machine and the longest possible service life, Rotabroach specifies a lubrication rate of 50 cubic millimetres per cubic metre of air the machine uses.

Both the Eagle and the Gator should have their motors flushed through with light lubricating oil after use. Depending on the couplings, it may be necessary to bleed the supply to disconnect the Eagle.

The Gator must be disconnected from the hydraulics when you change cutters or work on the machine.

Use and storage

• Do not expose the machine to rain, and do not use it in damp or wet places
• Do not spray water or flammable liquids over the machine
• When drilling overhead, use as little cutting fluid as possible and make sure it does not run into the motor
• Store the machine in a dry, locked place when it is not in use

Repairs and parts

Rotabroach states that all repairs must be carried out by an authorised Rotabroach service centre, and that modifications to the machine invalidate the warranty.

Parts for the machines we sell can be ordered from rail parts sales on +47 23 26 78 00 or using the parts order form on Spare parts. For daytime support, call +47 900 44 148.