A site dedicated to CNC of Mini lathes - the 7x10, 7x12, 7x14, and 7x16

Welcome to 7xCNC!

A site dedicated to computer numeric control (CNC) of Mini lathes - the 7x10, 7x12, 7x14, and 7x16

The chinese made mini lathes are cheap, widely available, and capable (with a little work). They are made in a number of factories and rebadged under many names including Sieg, LMS, Micromark, Harbour Freight, Grizzly, and Homier. The basic design is common to all but details and finish do vary.

Have a look at my conversion, or see what other conversions people have done.

I've just put up an article on a spindle encoder that allows software speed sensing and CNC threading.

I'm working on some software guides (mainly for linuxcnc, as that's what I use).

Posted by  7xCNC  March 28, 2013

Turn ABS pellets (cheap) in to filament (expensive)

Based on work by Hugh Lyman (Extruder I, Extruder II), FilaStruder, and bobt.

 

Parts:

Power supply: 12v 10a from Ebay for $12.25 shipped (search "12v 10a power supply")

12v 10a Power Supply

Posted by  7xCNC  January 6, 2013

Tooling is central to performance of any lathe.

Quick Change Tool Post

The best investment for a lathe is a quick change tool post (QCTP), and could be regarded as essential for a CNC lathe.

I'm using the 0XA QCTP from Little Machine Shop. It's designed specifically for small lathes and is a wedge type QCTP. It cost me $130 plus shipping but worth every penny. It comes with the tool post plus 5 holders - you'll want a few more, which can be bought for not too much (though a few certainly adds up) or made relatively easy if you have a mill. I'd heavily suggest getting the 2MT (Morse Taper 2) holder - it will allow you to mount drill chucks / collet chucks easily and therefore do peck drilling (no need to use the tailstock).

The 0XA QCTP was a simple bolt on for my 7x14 - just remove the old toolpost and stud and put on the new stud and toolpost.

Indexable tooling

Using standardised indexable tooling has a number of advantages on a CNC lathe. Firstly you can replace the cutting edge without having to redo offsets / tool information, and the geometry is always the same. Secondly most CAM programs have libraries of inserts built in, so you can easily have your tools set up in CAM and therefore have appropriate tool paths and avoid clashes with the workpiece etc.

Posted by  7xCNC  December 29, 2012

If you are going to use more than one tool in a part with a CNC lathe, you'll need an accurate tool table.

The tool table tells the controller software where the cutting edge is in space. This is necessary as the G Code tells the controller to move, for example from Z0 to Z10 but doesn't contain any information about where the cutting edge is relative to the lathe. For instance, if you are using a left cutting tool and a right cutting tool, the Z position of the cutting edge will be different (Z offset). Or tools might protrude different distances from the tool post (X offset).

Decide on a system for numbering your tools. Label your tools with these numbers (whiteout correction fluid works well for this).

In LinuxCNC the tool table can be edited manually - either by text file, or more easily via the tool table editor, found in the file menu. You'll need to do some manual entry to set up tool angles for tool display in the preview.

Posted by  7xCNC  November 10, 2012

5Bears (a great site on CNC machine building) has a good technique for turning down screws. It involves making a tight fitting collar to allow the screw to be accurately indicated mounted in a four jaw chuck. This is to ensure concentricity.

Posted by  7xCNC  November 9, 2012

NGCGUI is a subroutine system for LinuxCNC. It's conversational CNC programming. That means rather than designing a model in CAD then running it through CAM to get Gcode which you run via LinuxCNC, you can enter a few parameters directly into LinuxCNC and go.

It's great for simple machining, and in fact can cover the majority of lathe operations. You can build a whole program from a number of different subroutines. For example, you can turn a length to size, then thread part of it and put a radius on the end. There are all sorts of combinations possible.

There are a whole bunch of subroutines available (most in the LinuxCNC forum) and you can easily write your own.

Posted by  7xCNC  November 9, 2012

Z is the long axis of the lathe

Z0 is the end of the stock

-Z is then towards the chuck, and +Z towards the tailstock.

X is the cross slide

X0 is the centreline - the very point of the tool should be on the centreline at X0

+X depends on the machine, but in a converted manual lathe is usually towards the operator. And -X away from the operator.

Posted by  7xCNC  November 9, 2012

Simon C has done a very nice conversion, thread at cnczone.com. He's done a neat job with stepper covers, new coolant tray.

blades started with neat solutions using the stock screws and then built on it from there. Thread at cnczone.com

Posted by  7xCNC  November 4, 2012

My conversion is based on a Titan TL180V Minilathe from Titan Machinery, a machine tool importer in Australia. In stock form the lathe has ~400mm between centres, 65mm cross slide travel, 110mm swing over saddle, and 180mm swing over bed.

I'm using Probotix Probostep drivers + 280ozin steppers. I had this 3 axis left over from an upgrade to my CNC router. If I had my time over I'd go with a g540 - it does have two suplus axes, but has many features and easy wiring that make it well worth it. However, I can't fault the service from Probotix. I managed to fry a breakout board by shorting 5V with the USB power plugged in - Probotix sent me a new board, free!, when I emailed them about the problem.

I wanted a conversion that didn't increase the footprint of the lathe (much) but maximised the travel. I wanted an X axis that increased the travel to allow gang tooling.

I'm using 1/2" 6TPI ACME thread. It's very hard to find ACME thread in Australia. Fortunately there is a good bolt supplier close by that can get it. It cost me $50 for enough thread to do the lathe twice over. I made nuts out of plastic.

X Axis

X Axis V1.0.jpg

Posted by  7xCNC  November 3, 2012

For the princely sum of $6.50 I was able to get a jogging pendant going.

I bought a cheap imitation PS2 controller from ebay:

Ebay Joypad

I then followed a LinuxCNC wiki guide: Simple Remote Pendant using a $10-20 joypad with halui and hal_input and the adding more controls to pendant page

Note: To get the more complex joypad code working (with incremental jog) I had to comment out "loadrt near" and "addf near.0 servo-thread" in my main .hal file. I believe these are there for the spindle speed sensor, added by stepconf. In custom_postgui.hal I then increased the count of 'near' and renumbered the "near.n" (in the code example from the 2nd LinuxCNC page) for my spindle sensor.

Posted by  7xCNC  November 3, 2012

LinuxCNC (as of 2.5) has great lathe support.

LinuxCNC can seem daunting at first, and there is a common perception that you need to edit lots of code, but it's actually very easy to get going.

The stepconf wizard provides a graphical interface for setting up you machine. You can set lathe mode, driver settings, ports & pins, axis settings (and test them), spindles settings - all without digging through menus and obscure setting pages.