Thanks to those who responded on this topic. I was trying to identify the thread in order to buy a tap having avoided thread cutting in the lathe for so many years I had become paranoid about it. Well, since running was rained off today I grasped the nettle, called up reserves of "the old magic", took the stripped tube end and screw cut the existing thread further up the tube. I then cut off the stripped portion and relieved the other end to make up for the offcut. Bingo - collets are back in business. Truth is I have spent the last year working on a certain 5" Duchess and become slightly obsessed with it to the point where all workshop maintenance work was ignored. However the engine is now up and running and I have a few pictures to prove it. Would it be possible to put them on your website Alan? Regards, Barrie MODEL ENGINEERING DISCUSSION LIST. To UNSUBSCRIBE from this list, send a blank email to, modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line.