When you buy the collet chuck you have to buy a backplate for your particular lathe. In this case for a Warco WM240B.
The backplate is made from cast iron and was pre-machined to fit the spindle of the Warco WM240 lathe and also came with 3 off 6mm stubs with washers and nuts – this is a touch strange as the normal 3 and 4 jaw chucks supplied with the lathe are fitted with 8mm studs.
The good thing about the 6mm studs is that this ensures that the backplate aligns on the spindle with no offset forces from the studs.
One problem is that the chuck guard interferes with the toolholder and can make it jam when working this close to the spindle. I had to tape a block to the lathe to rest the guard on and give some clearance.
The step in the backplate is machined down.
Take care and measure lots of times and cut just once or you will end up buying another backplate.
The cutting tool is a Glanze TCT indexable tool, lots of cast iron to be machined and these tools make it very easy to get a good finish (see also: machining cast iron).
The step in the back plate machined down to size.
The holes are those for the studs that mount the back plate to the lathe.
Just offering up the collet chuck to ensure a good fit.
I marked the location holes for the chuck by placing it on the back plate and marking through with a scribe, ensuring that these did not line up with the existing holes for the studs that hold the back plate to the lathe.
I marked a 0 (zero) on the edge of the back plate so that I could always align it in exactly the same place on the lathe.
I used a tungsten carbide bit in the Axminster Flexible shaft – great tool, just wear a gardening glove on the hand that you use to hold the workpiece just in case you slip.
Very carefully centre drilling the holes that I had marked earlier.
The threaded hole that you can see in the foreground is the back end of that for the stub – I cleaned material away from these holes as well so that the chuck would seat correctly.
You can see the slight undercut around the base of the boss on the backplate, again to ensure the chuck locates on the correct surfaces.
These holes were then drilled out to 8mm diameter.
Very carefully removing any material from edges.
The backplate is turned over and clamped to the mill table.
Using the laser alignment tool that I made sometime ago it is easy to locate the hole.
The camera has caught the spinning laser light and you can see the circle glinting off the edge of the hole. The steps are:
- change the height of the head to get the circle of light the correct diameter
- move the x-y traverse to align the light
- change the height to get the diameter perfect
- change the x-y to get light aligned perfectly with edge
- stop the mill and lock x and y traverses
- remove alignment tool and fit countersink tool
All of the countersinks made and machined deep enough to sink the caphead bolt below the surface of the backplate.
I used stainless steel capheads for this.
All bolted together and with the studs fitted.
This shows the arrangement of bolts and studs.
In place on the lathe.
The backplate as supplied by Warco is quite large, but this adds to the moment of inertia and if anything helps with machining.
The zeroes align when fitting the chuck to get a very repeatable location of the chuck.
I used a dial gauge to determine the runout, ok at an angle, the needle just shows a hint of movement and no more.
That felt like a great result. I will check this again in a few weeks once it has been on and off the lathe a few times.
I also checked the alignment with a piece of stainless steel held in the chuck.
Again, the needle just moved, but not enough to make a measurement.
Price: approx £40 ER 25 Lathe Collet Chuck 100mm + £30 Lathe Back Plate for WM240 warco.co.uk.
I′m impressed. The price was not too high, the machining of the backplate took a couple of hours to complete, taking time to check and re-check. I have now used the chuck to machine some parts and it works really well. I now have quite a lot of ER25 collet chucks and so a healthy number of collets.