# Clausing Colchester Threading Issue.



## tecteachr (Apr 22, 2015)

I set the control levers to LB1SW to cut 16 TPI on a 3/4 shaft. When I tried to chase the thread with a 3/4-16 die, I found the thread did not match the die. I ran the die over a known good 16 TPI 3/4 shaft & it matched perfectly. Either I am not making the correct lever position setting, or my lathe gearing is not what I thought it was. The lead screw is 1-1/4 D & 4 TPI. I did it twice to check my procedure & it did exactly the same thing. The pitches don't match. both the crossfeed & compound screws are English thread. Any help appreciated


----------



## wa5cab (Apr 22, 2015)

tecteachr,

I have no idea what the answer to your question is.  But unless Clausing never made but one lathe with a 1-1/4" dia. lead screw, you should state the model number of your machine and in some cases, probably the serial number.


----------



## seasicksteve (Apr 22, 2015)

On my colchester the L setting is established by the position of the change gears under the cover have you verified that the change gears are oriented correctly. Is your threading tool geometry correct? If you are feeding with the compound is it set correctly? Try verifying the pitch with a gauge or a tap of the same pitch. Can you determine if the pitch is incorrect or if the thread form is wrong?


----------



## T Bredehoft (Apr 22, 2015)

Put the drive in neutral, (with the electricity off) put a 1" dial indicator on the way, measuring movement of the saddle. engage the threading gear and by hand rotate the chuck,   observing how much the saddle moves. This will tell what pitch it's set to.  (divide one inch by the movement of the saddle, this will tell you the pitch.)


----------



## tecteachr (Apr 22, 2015)

The lathe is a model 8000, 15". I got in too big a hurry with my frustration. I wondered if the work had somehow slipped a bit but don't see how it could happen the same with two attempts.


----------



## Carlboe (Apr 23, 2015)

tecteachr said:


> The lathe is a model 8000, 15". I got in too big a hurry with my frustration. I wondered if the work had somehow slipped a bit but don't see how it could happen the same with two attempts.


Try engaging about a inch or so before cutting  to remove all play in the apron. Are you backing out on the cross slide and coming back in to remove play? I hope this helps


----------



## seasicksteve (Apr 23, 2015)

tecteachr said:


> The lathe is a model 8000, 15". I got in too big a hurry with my frustration. I wondered if the work had somehow slipped a bit but don't see how it could happen the same with two attempts.


On that model IIRC the L is set by the lever L or H so ignore previous reply. Im not sure if the gears under the end cover can be set up in different configurations to achieve certain thread pitches, you might want to check there and see if they are set up correctly. There is a shear pin on the lead screw where it exits the gearbox, it is under a spring loaded washer that can be rotated to expose the pin cant hurt to look there to be certain its driving 100% from the gearbox. Just a couple ideas


----------



## tecteachr (Apr 25, 2015)

Many thanks to all who replied. I found it had to be slippage of the part in the rubber collet that caused the problem. I mounted an indicator against the carriage & the value was as it should be. (.0626/revolution) I don't see how that small a load could slip.


----------



## seasicksteve (Apr 25, 2015)

Glad you got it figured out. I have a Pratt Burnerd collet chuck on mine that chuck is the shizz for sure.


----------

