I have a set of ER32 collets and am considering making a collet chuck for my Viceroy Lathe. It would be similar to the ERM100 shown on
The only question is what material? As this is going to screw onto the spindle chuck mount 1.5 inch x 8 TPI I feel that Cast Iron would be best, though I am a bit concerned about the longevity of the relatively fine Collet nut thread.
Obviously my existing collet head fits the MT3 spindle taper but does not allow bar "up the spout". Overhang would also be reduced with a proper spindle mount head.
Richard Hi, I made one of this type of collet chuck several years ago for my Boxford which has the same spindle nose thread as your Viceroy. I adapted a design that was published in EIM in 2003 (check your mail) and it has worked hard with no problem whatsoever. I made mine from a piece of "free cutting mild steel" I bought from my local stockholder; at the time enough to make three bodies cost =A315. The nuts were made from the same material. While I haven't been in the shop much over the last 6 months prior to that they were in almost daily use for three years and show few signs of wear. I do take the trouble to keep them really clean though as the relatively "soft" collet seat would no doubt mark with any chips. I did think of using a "hardening" steel but decided that I could just recut the seat if, at any time, it showed any damage; it hasn't yet. If you are using these in a professional shop then something more exotic might be justified.
The closing force required on the nut, particularly when holding imperial sizes in the metric collets is quite large and I'm not sure I would be confident using Cast Iron. I've not got time to "do the maths" on the thread strength but just feel that steel would be much better in this situation, particularly if you ever need to hold a milling cutter in the chuck. These nuts which are the most "trying" part to make are now available form several suppliers at reasonable cost if you feel flush, I found the exercise interesting so made my own.
The last collet chuck I needed was for my BH600 and as time is currently short I bought a backplate mounted version from ArcEuroTrade. This has been excellent and once set up (easy with the backplate mounting) has proven to be accurate and repeatable. While many think the overhang would be increased with this type it is actually the same as the Boxford one I made.
Apologies for another rushed response and on this occaision my "opinion" is born purely of experience, I just haven't had the time to do the research and thought for a "theoretical" response.
Tony I have made an ER32 collet, chuck for a lathe I have been making, from mild steel and it seems ok so far. I made it from 3" bar and it has a
1.875 x 16 tpi nut I also made. To avoid making the eccentric removal part I made two .312" dia x .040 thick washers csk for 6 BA screws. The washers were made from silver steel hardened and tempered. I fitted the washers on an 18.5mm pcd at 120 degrees to each other inside the nut instead of the eccentric extractor. The collet can be easily fitted in the same manner as for the eccentric nut. The dimensions are just a guide. Regards Alan
Thanks for all the comments with a particular "thank you" to Keith for a long scribe and a PDF. I will be using steel, got an offcut allocated. I will buy the nut, in fact a bearing type which increases the available clamping force. I did consider the backplate and bought collet chuck option but felt it looked "ungainly". The "bought direct from Hong Kong" items were interesting. Particularly as the ER11 range did not go as small a bar size as the ER16 and ER20. My collet set is 18 off from Nominal 3 to 20. If I find I need smaller then a few ER16 plus another "home made" chuck would be the way to go. The vendor is noted.
All I need to do now is work out the change wheel set to give me 8 TPI from my 3mm leadscrew.
BTW If anyone needs any 1 3/4 brass bar I know of a source at a good price. 4 foot lengths. (they are bar ends!)