A 7x12" mini lathe is an excellent addition to the home workshop. With some patience it can produce parts to a high standard. As with most cheap import tools, the mini lathe will require modification and repair upon purchase.
Initial Modifications
Visually inspect the earth connection behind the motor controller housing. Unscrew the terminal from the headstock and remove any paint from the contact area. Reconnect the earth and test with a multimeter. Earth continuity must be less than 1Ω from the chassis to the earth pin of the cord.
Inspect the mains fuse and confirm that it is T4A. A higher value will cause significant damage to the controller board under fault conditions.
Mechanical:
Take apart carriage, slides and apron, and clean with kerosene to remove grinding dust from the factory.
Deburr all sharp edges, including the bed, carriage assembly, and tool post.
Glue sheet metal over holes in chassis to prevent swarf getting into the motor.
Use short screws to fill tapped holes in carriage, again to prevent swarf ingress.
After the lathe is full re-assembled, take some time to carefully adjust the gib screws in the cross slide and compound slide.
Align the tailstock. This can be done quickly by putting a centre in the tailstock and aligning it to a piece of stock in the 3 jaw chuck which has been turned to a point. Having the two points aligned when the tailstock is both the fully extended and fully retracted will ensure that the tailstock is parallel to the lathe bed.
A more accurate test is to turn a piece of stock, held between centres and driven by a dog, along the length of the bed. The diameter is measured at each end to determine the tailstock offset.
Periodic Maintenance
Remove the sheet metal motor cover and check that no swarf has entered the motor housing. If chips short against the motor brushes, the control board will fail.
Oil the bearing surfaces and lead screws, and apply lithium grease to the change gears.
Repairs
The printed board assembly of the mini lathe is commonly marked SCR-340 with a sticker on the heatsink. The silkscreen on my printed board is marked FzDz Ver1.33.16.08.08 A, but this seems to vary between manufacturers.
The circuit and printed board design appears to be a copy of the KBLC-240D. Unfortunately, the component names are different.
Use a multimeter to diode check D2 and D3, and check resistance of R8. Replace any blown components.
Further modifications
- A sheet metal chip tray was added to the front of the carriage to prevent swarf building up on the ways.
- DRO made with cheap digital calipers
