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7x12 mini lathe in fetching blue!

Carriage lock for 7x12 mini-lathe

When performing an operation on the mini-lathe that does not involve moving the carriage back and forth, eg facing or parting, one locks the carriage in position with the half nut level. This does not work very well. In fact, its utterly useless. Wobble the carriage wheel back and forth and you will find that the carriage does move around a bit.

There are two movements. First, the carriage moves along the bed slightly with the backlash in the halfnuts. Secondly, the carriage will twist slightly. Adjusting your mini-lathe properly will minimise this effect, but to remove it completely would entail tightening the carriage gibs to the point where they do not move any more.

If the carriage moves during a facing or parting operation, problems occur. The tool wedges in the job, ruining the job and stalling the lathe. The facing operation ends up with a curved end instead of flat. All bad.

The solution is to use a carriage lock. The normal Chinese mini-lathes do not feature carriage locks, but there are many ways to fit one. I have seen a lot of extremely complex designs on the Internet for carriage locks. I soon decided they were too complicated for me. The very simplest approach is to drill a hole right through the carriage and tap it. Then screw in a brass bolt - tightening this bolt wedges the lathe in place. However, this does tend to lift the carriage off the bed of the lathe slightly.

My approach was to drill a hole in the carriage aligned with the gap between the ways. I then cut a 37x20x4mm piece of iron from a bar purchased in B+Q. I drilled a hole roughly in the centre and tapped it. The small strip of metal goes under the ways, and a hex head bolt is used for screw down the hole in the lathe and screws into your tapped hole. The scrap iron needs to be cut wide enough to fit easily between the ways, and it needs to be thick enough to allow enough thread to hold the bolt. At least 5mm.

To engage the carriage lock on the mini-lathe you just need to tighten the bolt with a hex driver. The clamps the carriage down onto the ways. Ideally I should make another one on the other end of the carriage to apply even pressure.

There was already half a hole in the carriage, perhaps for holding a traveling steady. I don't have a traveling steady, and if I did use one, I'd not be needing the carriage lock at the same time.

I advise removing this metal strip when doing power driven cuts such as threading to prevent any risk of the metal snagging and mucking up your cut.

Mini-lathe Carriage lock pictures

carriage lock on a mini-lathe

carriage lock on a mini-lathe carriage lock on a mini-lathe

The 2 silver nuts in the pictures are just used as spacers to save the hassle of shortening the bolt.

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