Contents - Index - Previous - Next

Care of a Lathe


Keep all parts of the lathe bright, clean and free from abrasive materials, dirt, dust and corrosion. Lubricate the lathe according to the maker's instructions. Keep all slideways lubricated: use, for example, Rocol Slideway Lubricant Spray, available from Axminster Power Tool Centre www.axminster.co.uk and other suppliers.

What to Check if a 5CNC Lathe Stops Working
The 5CNC lathe is very reliable but electrical or electronic faults sometime occur.

Isolate the lathe from the electricity supply.

Remove the back of the control cabinet.

Check the following possible causes of failure:

1) In the top, right-hand corner of the control cabinet there is a large ceramic fuse in a screw-top fuse holder. Sometimes these fuses just die of old age. Test the fuse and replace it if necessary. In the UK, replacement fuses are available from RS Components Ltd. If the replacement fuse immediately fails check item 2 following;

2) Further down the righthand side of the control cabinet, on the power supply circuit board, there are two (on some lathes three) large electrolytic capacitors (about half the size of a beer can) all mounted in a row. One of these may have developed an internal short circuit. Check them and, if this is the case, replace all of them, not just the one which failed.

3) Just below the fuse, 1) above, there is a bridge rectifier. If the lathe does not move and the fuse, 1) above, is OK, it is likely that this component has failed. Replace it with one with a higher current and peak inverse voltage ratings. Failure of this rectifier does not always cause the fuse, 1) above, to fail.

Speed Readout and/or Threading Synchronisation Failure
The spindle speed sensor is a slotted opto-switch mounted inside the drive belt cover. A metal disk, with 100 holes round its periphery, is mounted on the lathe spindle and passes through the slot of the opto-switch. As the disk turns, the holes make and break a light beam which passes across the opto-switch slot. This generates 100 electrical pulses per spindle revolution which are counted and processed to give a spindle speed readout.

The threading synchronisation sensor is also a slotted opto-switch mounted alongside the speed sensor slotted opto-switch. A single slot in the metal disk triggers a single electrical pulse in each lathe spindle revolution.

If the spindle speed readout or threading synchronisation fail, it could be that dust has clogged the slotted opto-switches. It may be possible to blow, or suck, the dust away. If that fails to resolve the problem, it may be necessary to remove the slotted opto-switches to that their slots can be cleaned with a brush. When the slotted opto-switches are replaced, great care must be taken to re-align them with the 100 hole disk.

If cleaning fails to solve the problem, it is probable that the integrated circuit which receives and conditions the signals from the slotted opto-switches has failed. This integrated circuit is an LM339 operational amplifier and, on the 5PC lathe, it is located on the small circuit board with the four DIP switches in the top righthand corner of the lathe control cabinet. Replace the LM339, taking care to install the new one the right way round. It is suggested that the new one is mounted in a socket for ease of replacement in the event of future failure.

Clean Down at Manual Tool Change