Here's a post about an adaptor I have just completed. It replicates the D1-3 spindle nose of my lathe as a stand-alone body that can be bolted to a machine table or rotary table, allowing my lathe chucks to be used for work holding elsewhere.

It's been quite an interesting exercise figuring out how to design, machine and assemble it to deliver the functionality I wanted from it. I'm not patient enough to be able to write this up as a magazine article and it's questionable if many people would want to make one anyway. However, I like reading about other people's exploits and ideas, so it seemed only reasonable to post some info on the forum in return.

I have a variety of chucks and fittings for my Colchester Bantam, all of which share the D1-3 Camlock system. The Camlock system uses a combination of a taper and a flat face to locate the chuck concentric and perpendicular to the lathe axis. The D1-3 size also uses 3 eccentric cams to pull the chuck against said face and taper. They act against 3 pins that stick out of the back of the chuck. As I now have 3-jaw, 4-jaw and collet chucks as well as a large faceplate and driver plate, it seemed to me that for some applications it would be very handy to be able to mount any of these either directly onto the milling machine table or onto the face of the rotary table.

The Camlock series dimensions are defined in the international standard ISO 702-2. I was able to locate a copy using the combined power and might of the internet and the MEW forum and thus work to the specification rather than having to rely on my own measurements. I started out by procuring a 2" length piece of mild steel of the nearest nominal diameter (4&quot. I set this up carefully in the 4-jaw, faced it off at both ends and then bored it out to 43mm to maximise the work holding capability. Finally, I formed the locating face and taper. At this point I had a spindle nose that fitted the chuck nicely but without any means of holding it on or driving it.

As I would be mounting the adaptor with bolts into the table in use, I drilled and recessed 2 holes at this stage, figuring that I'd find them useful for holding the adaptor during the machining operations. In some ways it would have been more convenient to have had 3 bolts but my rotary table has 4 slots. It was about then that I started to consider what a tricky challenge it would be to position all of the various radial and axial bores within the adaptor body along with the existing 2 bolt holes. It would require some devilish 3D calculations to place them all without clashing.

At this point I installed a 30 day trial demo of Alibre (now called Geomagic Design, baby) and created 3D models for the existing body and the key elements of the D1-3 system, namely the 3 cams and the 3 radial (cam) and 3 axial (pin) bores. I was able to vary the angle between the 2 existing bolt holes and the rest of the components to end up with the best relative positioning by trial and error. With the hindsight now provided I could see that a larger diameter body would have been advisable but I wasn't about to copper up again for another lump of steel. I was unable to avoid one of the bolt head recesses breaking through into one of the cam bores but I figured I'd be able to modify one of the cams and thus make the whole thing workable. I also placed the cam retainer pins on the rear face of the adaptor for simplicity (you can't do this on a lathe nose). I didn't fancy trying to machine the square chuck key holes in the cams, so changed them to external hex heads that I could mill on the rotary table and tighten with a spanner or socket. I also altered the length of the cams to suit the diameter and bore of the existing body. With these 3D CAD systems you can actually spin the cams in their bores and see how the eccentrics move. Groovy.

The blessed thing actually went together like the CAD model and it works like the Real Thing fitted to the lathe. I hardened and tempered the cams using a blow lamp and a bucket of water.

One of the first jobs for the adaptor may be to machine some extra slots in the faceplate. It only has 4 radial slots and I fancy a couple of extra slots to give more options for holding work. I'll mount it on the rotary table and then cut said slots with the aid of the DRO for accurate positioning.

There are several things I’d conclude from this exercise. I certainly wouldn’t have been able to calculate and optimise the correct positioning of the various bores manually. I couldn’t have positioned them correctly at the machining stage without the rotary table and the 3-axis DRO. The 3D CAD (the basic version of Albre) was relatively straightforward to get up to speed with, despite some undocumented features and indifferent technical support. And finally, I would have saved myself a fair bit of time and effort if I’d coughed up for a slightly larger blank to begin with. Overall a fairly satisfying result and one that pleasantly surprised me in terms of accuracy and relative lack of human error.

Hope that was interesting!

Muzzer