The Holbrook B8 is a classic 4" swing (4 1/4" centre height) tool room lathe with many interesting and useful design features see . Mine has been modified by a previous owner to take a Myford slotted cross slide together with an infinitely variable hydraulic speed controller.
However it has a good but oversize four jaw chuck and a sadly worn three jaw chuck which lacks a set of external jaws. Does any one know where I can source a couple of suitable chuck back plates together with a third for an additional alternative face plate?
The spindle nose measures up at..
7/16" of nominal(?) 1 13/16" register behind the thread (1.810" actual) 1/2" of 1 3/4" x 7tpi thread (N.B. this would seem to be 1 3/4" BSF in which case the core diameter should be 1.567") 9/16" of nominal(?) 1 9/16" register in front of the thread (1.551" actual)Perhaps I ought to be able to make them on my own B8. The standard gear box goes up to (or is it down to?) 14tpi and presumably doubling the size of one of the change gears (or halving the size of the another) is all that is required to get 7tpi. But the process also involves collecting a number of preliminary and necessary round tuits. Of these, the only round tuits already in my possession are three suitably shaped round pieces of cast iron together with what appears to be a round go-no-go gauge marked 1.807" and 1.827".
I presume that another essential round tuit will have to have the shape a dummy spindle nose. A suitably shaped chunk of aluminium is in my possession. In view of its proposed purpose (as a one-time-use gauge and nothing but a gauge) is this suitable material?
However the most significant tuit of all and the one that is not yet in my possession is the necessary courage to start.
Comments (hopefully helpful, encouraging or both) gratefully received. Or is this a suitable exercise for someone in the CNC brigade?