7X12 Mini Lathe

August 30th, 2008

A few weeks ago I splashed out on something I have wanted for a long, long time. A lathe!

lathe1 My 7×12 mini lathe.

This is one of the cheap, Chinese mini lathes. The 7X12 means it has a 7 inch swing and 12 inch length. These little lathes are quite crudely made but with a little work they can be made to perform quiet well. They are easily good enough for the generally imprecise things I am making. They do require some fiddling to get them working nicely and there are various modification you can do to make them easier and nicer to use. I have done two so far.

I won’t go into too many details. If you search Google for Mini Lathe you will find some very good sites with far more information that I can post here.  I got the ideas for these two modification off sites such as these. The first is an apron chip guard I found at www.mini-lathe.com

The apron on the mini lathe is completely open at the back meaning chips and swarf can get in between the two gears used to move the carriage along the bed. I did what a lot of others have done and made a plastic cover from 3mm thick acrylic scrap I had laying about. I drilled the hole for the large gears shaft to poke through first. I enlarged it by hand with a tapered reamer until it was a close fit. I then put the plate in position, traced around the outline of the apron and cut the acrylic to size. Next I drilled and tapped three holes to take 3mm screws to hold the plate in place. I did find with the plate screwed down the little wheel was held down by it as this gear protrudes ever so slightly from the apron. I used three small brass washers to allow the plate to stand off slightly. This of course leaves a gap around the edge of the plate which is no good. To fill the gap I simply ran a bead of hot glue around the edge of the acrylic and then screwed it in place. The glue filled the gap nicely even though it doesn’t actually hold anything in place. All the oil on the apron means the glue won’t actually stick to it.

chipguard1 Apron chip guard.

The second modification is  much more complicated. The mini lathe arrives with only a simple nut and plate to lock the tail stock in place.You undo the nut, slide the tail stock into position then tighten the nut using a spanner. This is a major pain in the neck especially since the tail stock doesn’t have a great deal of extension in it. If you want to drill a deep hole you must position the tail stock, drill to the end of the extension, retract the drill, loosen the tail stock, slide it closer and then repeat it all over again.

I found a nice design at http://www.gadgetbuilder.com for a cam lock. Big lathe usually have this feature. It is a lever on the tail stock you use to lock and unlock the tail stock to the bed. It makes reposition it much easier and makes the lathe a hell of a lot easier to use.

Extensive details are available from the site above. The dimensions are not critical so I winged it as I went along and used whatever scrap bits I could find (leftover MGB bolts as it turned out!).  First I made up all the parts. There are three main parts that need machining. Of course you use the lathe to make up the parts to fix the lathe!

camlock1 Cam lock parts.

First, on the left, there is the cam and handle. In this design this passes through a hole you drill in the back of the tail stock. I machined the cam from an old bolt and the handle is just a length of steel I had in the scrap bin. I believe it is an old motor shaft! I brazed the handle to the cam so there is no chance of this coming loose! Next to the cam is the main bolt that passed down to under the bed. To the right of that are the thimble and nut. I had to machine the nut thinner so it would clear the supports under the lathe bed.The steel plate is just some scrap 3mm steel I had lying about.

camlock2 Parts assembled.

This shows the parts in their assembled position outside the tail stock so you can see how they fit together. Basically how it works is the cam passes though both the thimble and the bolt. As you turn the cam the bolt will ride up and down on the cam profile. This changes the length of the entire assembly. On the lathe you set it up so that at the maximum length the tail stock is free to slide upon the bed. As you turn the cam and shorten the entire assembly this brings the lower plate up and into contact with the bottom of the bed clamping the tail stock into position. You only need a quarter of a turn or so to do this.

To get the whole assembly to sit square I did have to mill the base of the tail stock (the casting of it is very rough) so that the thimble is level. I also drilled the hole that the cam passes though. I somehow managed to get this a little off centre but luckily the bolt is much smaller than the hole in the base of the tail stock so there is plenty of room for error here.

modifiedtailstock Milled tail stock base.

Everything is assembled on the tail stock which is then slid into place on the bed. I used some blue Loctite on the nut that holds the locking plate in place and carefully adjusted the nut so that the tail stock is firmly locked in place with the handle vertical. You turn the handle a quarter turn clockwise to unlock it (it actually needs very little turn to unlock). I made the handle short enough so it doesn’t interfere with the locking level on top of the tail stock.To stop it rotating down past 90 degrees I drilled and tapped for a 3mm screw. I didn’t have a long enough screw to make a stop so I am temporarily using a short screw with a length of plastic hose pushed over it.This works quite nicely as you can then easily push the lever to the unlocked position and it just drops silently out of the way against the plastic hose.

camlock3 Handle and stop.

I used bearing grease on the assembly before installing it and then used a small circlip to hold the cam in position once everything was in place. It is all bare steel finish but everything on the lathe is oiled and greased regularly so there is little chance of it rusting.

Now I need to start making things on the lathe rather than making things for the lathe!

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5 Responses to “7X12 Mini Lathe”

  1. Amber Says:

    Just when I thought the A team music box filled my life the Lathe came along. Now I know the true meaning of life….Thanks you mini lathe

  2. Brian Says:

    I’ve never lathed… How do you clamp the shaft off-centre to turn the cam section? Do you need a four-jawed chuck?

  3. Simon Says:

    You can use a four jaw and set it all up that way but it’s easier to use the three jaw and you put a shim against one of the jaws. I just used a thin piece of aluminium about 1.2mm thick.

  4. Cheap 7X12 Chinese Mini Lathe | HACKOLOG - Amazing Hacks and Mods Says:

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  5. Jerry Reyes Says:

    hi, how can i avail this mini lathe machine? i’m very much interested in acquiring this one. i’m from the Philippines.
    thank you