Well tonight I finished (well not quite, more on that later) my ER11 collet system for my lathe. After cleaning everything up I decided I might snap some pics to show everyone exactly what I've been ranting about these last couple of pages
First up I've got a picture of the lathe as it sits on my desk. I had just cleaned up after cutting down the drawbar hand wheel so there is no cutter mounted in the tool holder. Additionally you can see my shiny new collet chuck and drawbar mounted instead of the normal chuck:
OK so normally it turning anything with a decent diameter (greater than say 3mm) we use the normal 3-Jaw chuck, as seen in the next photo. It's really quick and easy to use but as I said has size limitations: anything less than 2mm diameter it simply can't hold properly. It's important that the lathe is able to hold the material perfectly centred for machining. The shaft that the chuck is mounted on is hollow all of the way through, so you can stick really long bits of material in there and they just protrude out the other end of the headstock.
In order to machine very small diameter material (down to 0.5mm styrene rod) I bought an ER11 collet set and an ER11 Morse Taper #1 (MT1) collet chuck. This mounts onto the lathe in place of the standard 3-jaw chuck (as seen in pic 1). I chose the ER11 collet size because the same size is used on my new CNC router. The collets themselves can only hold a piece of material within about 0.5mm of the collet's rated diameter, so you need a full set to cover all sizes. I got a set from 0.5 to 7mm in 0.5mm increments.
Here's a picture of the collet chuck holding some 2mm styrene rod:
The collet chuck is tapered to that it fits into the headstock spindle, however there's nothing to really hold it in place. What is required for this is a drawbar: simply a threaded rod which screws into the back of the collet chuck and locks it in place. I elected to make a drawbar from an M6 by 100mm long steel bolt. I sawed off the bolt head and then tapped about 6mm of thread onto that end so that I could thread on a handwheel for tightening. The handwheel I had a friend machine out of steel (because he has a knurling attachment to finish it off with) and which I then did final machining of the surface which contacts the spindle on this lathe. The poor little lathe didn't like cutting steel but she soldiered on and I got there in the end.
Man it made a mess! I don't recommend machining steel on the hobby desk in your bedroom. I had to get the vacuum cleaner out afterwards to clean up...
Here's a breakdown of the collet system parts for the lathe. Starting top left and working clockwise we have:
- Collet chuck
- Collet
- Collet nut
- Drawbar
- Drawbar handwheel
Already I've been machining styrene rod as small as 1mm diameter and the collet chuck system works perfectly. In all I'm very happy with it!
Oh the reason I said that it's not quite finished is that I need to drill a hold down the centre of the drawbar so that material can extend out the back of the headstock like when using a normal chuck. I can use this lathe to do that (but I'll be sure to take it into the garage for more metal machining!).
Next trick will be to make a radius turning tool (since the Taig one I bought has no chance of fitting on the Sherline machine) and vertical slide.
Oh yeah I can make that....