Milling with a lathe

Milling can be carried out on a lathe, and it can do a good job, once a few small modifications have been made.  A resonably solid lathe can mill steel quite capably.

Accuracy within a thou of an inch is no problem.

Before the advent of relatively cheap Asian milling machines it was quite common for this type of work to be carried out on a lathe.

Considering the limited amount of milling I do, I couldn't justify the space nor expense of a large and heavy stand alone milling machine, and a close examination of the lightweight hobby versions left me decidedly unimpressed.

So I set up my Chinese CQ9325  10 x 18 lathe to do the odd job that came along  - see below. 

mill in lathe

Asian lathes are well suited to this sort of work as they generally have a flat cross slide, which allows easy installation of a generic mill slide.

This video shows how easily the lathe machines a 10 mm slot into some hard steel plate.

Being able to do jobs such as slotting and cutting keyways on a lathe is a big plus.

I deliberately bought a lathe with a Morse No. 4 headstock to keep costs down.  Anything larger than this will be much more expensive to purchase spindle accessories for.

It's a fairly simple and quite cheap exercise to set up the lathe.

What you need

You require:

- a vertical mill slide able to be attached to the cross slide,

- a small vice to be mounted on the vertical mill slide,

- a collet chuck and draw bar to fit the lathe spindle,

- some collets,

- and some milling cutters.

The vertical mill slide I purchased is a fairly solid Chinese made unit, cast iron, with a 6 x 4" table and milled T slots - $200 AUS.  The table pivots across a 180 degree axis.  It's OK for the money, but there is slight divergence in the dovetails.

Setting up the lathe

If your lathe has "T" slots in the cross slide you can simply use those to mount the mill slide.

To fit my lathe I had to precisely drill and tap three 10mm holes into the top of the cross slide, to bolt the vertical slide down - see below.

The two smaller holes on the left mount the tool post,  the other three are for the mill slide.

This is not a particularly difficult job, it just requires care in aligning and drilling the holes.

As you are tapping into cast iron (which is relatively soft) make sure you get maximum thread depth and penetration. 

milling with a lathe

Set it up so that a cutter can can traverse the full width of the vice jaws in relation to the available cross slide travel.

The tool post is removed for the vertical mill slide to be used - you can see two Allen headed bolts where it used to be.

Here's a video giving an insight into setup and effectiveness.

On some jobs, regularly switching between the lathe and the mill can be a nuisance, but that's the price you pay for using one machine for two functions.

If you intend to do a lot of milling, then it would be worthwhile buying a decent full sized, dovetail column milling machine.  These cost more than most small lathes.

mill slide

But for small jobs and occasional use a mill slide on a lathe works well.

You do have less travel in comparison to a full sized milling machine, and it's a bit harder to set up jobs accurately - as work is orientated on a vertical plane.

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