Thread dial indicator.

[Raymond AndersonParticipant @raymondanderson34407]

Hello all,

                   My small lathe required a new TDI although the new one is different my question is as follows,  Can I start a thread on any mark or number regardless of the pitch as long as I  re-engage the half nuts on the same number or mark every time? ie If I start a thread on number 2 can I use 2 every time?

                                                       Regards,

                                                  Raymond. 

[Raymond AndersonParticipant @raymondanderson34407]

[KWILParticipant @kwil]

Generally no is the answer. It depends on the pitch of the leadscrew and the thread being cut. For instance, with an 8tpi screw, any thread can be picked up if it is a multiple of 8, ie 16, 32 tpi etc. Cutting a metric thread on an imperial lathe do not disengage but reverse back and then forward to take up the backlash.

[Raymond AndersonParticipant @raymondanderson34407]

Thanks KWIL,

                              Does it make any difference that the lathe is metric and the threads to be cut are metric? The leadscrew is 4mm pitch acme and the small gear on the TDI has 15 teeth. and the TDI has 4 numbers 1,2,3,and4 and a line between each number.     I don’t really like to reverse the lathe every time so I must try to get this TDI sorted out.

                                                         Best wishes,

                                                      Raymond. 

[Raymond AndersonParticipant @raymondanderson34407]

Hi all,

             Here is some more info for anyone who can help with the above problem, The original TDI had 2 gears 1 with 14 teeth and the other with 15 teeth. The new one has got 12 teeth [I thought it had 15 teeth]  My biggest problem is knowing which marks on the TDI I need to engage on for any given pitch. Also I never have to cut imperial threads so, that will be 1 less complication.  As KWIL said I can cut direct multiples of the leadscrew pitch no problem ie 1.00, 1.50,2.00 3.00, 6.00 and 9.00 but something like 1.75 is a no no. Also what is peculiar is the leadscrew appears to be 4mm pitch acme so why am I able to cut the above threads which are multiples of 3? 

                                                       Regards,

                                                      Raymond.

PS, No such trouble with the DSG 

                                               

                                                  

[Author]

Posts