Educate Me On Thread Dials

Another take is to never disengage from the lead screw until the thread is finished. Probably the best course of action for a metric thread on a G0602. This technique has worked extremely well for me.
 
Thanks for all the feedback.

Well I got the dial made last evening and installed it this evening. I think I got lucky on this gear fitting as it turns out this Shepard has a 5 TPI lead screw. I should have checked that before I posted and I would have felt better about this working. I still have to mark the graduations but It should match up in at least 2 places on the dial.

This is an old treadle lathe that was in pretty awful shape when I got it. I got it running on a tread mill motor. I did not wire it so it will reverse so I pretty much have to count on a dial.

This lathe is my winter project and while I will never use this for serious work I do want things to function properly.

I am heading back out to try Derfs suggestion with the sharpie. I will report back on how it works out.
 
This is going to work. I marked on the dial and the outer ring. I marked the carriage position. I moved the carriage until the dial complete one revolution.
I then marked the carriage position again. It measured out to be exactly 2 inches travel. I moved the carriage all around and when I stopped the carriage on the marks on the bed the marks on the dial always lined up.
I chucked up some stock and tomorrow will set up the change gears for some thread cutting.

After reading the posts about not disengaging the halfnuts and running it through the tests I did realize that this thread dial is unnecessary as there is a lever that allows me to reverse the travel of the carriage with out stopping the lathe.

At least it was a fun project and it's there as option if I need it.
 
I think the thread dial is mostly used as an optimization for doing threading, to do it faster. Running the lathe in reverse for the threads probably takes longer than just releasing the half-nut and cranking it back by hand, then tightening the half-nut and lining up the dial to the right spot.
 
:shhh:Just so I don't forget I always just engage the half nuts on the same number every time. So my dial would just need one number.
 
gwarner said:
This is going to work. I marked on the dial and the outer ring. I marked the carriage position. I moved the carriage until the dial complete one revolution.
I then marked the carriage position again. It measured out to be exactly 2 inches travel. I moved the carriage all around and when I stopped the carriage on the marks on the bed the marks on the dial always lined up.
I chucked up some stock and tomorrow will set up the change gears for some thread cutting.

After reading the posts about not disengaging the halfnuts and running it through the tests I did realize that this thread dial is unnecessary as there is a lever that allows me to reverse the travel of the carriage with out stopping the lathe.

At least it was a fun project and it's there as option if I need it.
Click to expand...
You will want to check the reversing mechanism on the lathe. If your reversing system reverses the drive from the motor to the spindle (highly unlikely, since modern lathes reverse the motor rotation) you wold be OK.

The reversing gears on lathes that I have seen disengage the gear train from the spindle to shift from forward to reverse. You should never disengage the gear train while threading as it almost always will lead to a loss of lead screw registration.

To thread while leaving the half nuts engage, you have to reverse the motor direction to run the carriage back.
 
dave_r_1 said:
I think the thread dial is mostly used as an optimization for doing threading, to do it faster. Running the lathe in reverse for the threads probably takes longer than just releasing the half-nut and cranking it back by hand, then tightening the half-nut and lining up the dial to the right spot.
Click to expand...
It also allows threading to a shoulder. You can do so without disengaging the half nuts but you would have to stop the lathe early and finish the thread by hand turning the spindle.
 
Tom Lipton, OX tools, demonstrates a method of cutting metric threads to a shoulder, using the half nuts to disengage. The actual process is shown about 7:20 into the video. I have tried it myself and it works.
 
Without a thread dial it's more difficult to do a multiple start thread which some gun barrels require.


Steve Shannon, P.E.
 
Well I took the dial off tonight because I will never use it on this lathe. It worked just as you would expect a dial to work. If I caught it on an even mark it matched up and cut the same spot.

The reason I took it off is this lathe has a lever that you engage and have to hold in place to make the lead screw turn. Hold it to the left and it rotates clockwise hold it left and it turns counter clock wise. The carriage moves the direction you hold the lever. During my tests tonight It works very well. Engage the half nut Set the depth on the compound. Engage the lever left. Let it travel to the end of the cut. Hit the lever to neutral back off the compound. Hit the lever right Let it travel to the right and set the cut a smidgen deeper. Rinse and repeat until you have threads.

When trying to use the dial I found it difficult to hold the lever, engage the half nut, run the compound and focus on the dial all at the same time.
 
You must log in or register to reply here.
Back
Top