Who Needs A Thread Chasing Dial?

[MetalMuncher]

George,

There must be more to the blinking light scheme than a contact that causes the light to blink with each rotation of the leadscrew. My leadscrew rotates 16 times for each rotation of the thread dial so the blinking light would only work for certain thread pitches.

I do a fair amount of threading in both metric and Imperial so I added a dog clutch to my 7x12. The dog clutch automatically synchronizes for either thread type and does it in one spindle rotation so it's faster than a thread chasing dial.
Video of it in use here:

John

Whether or not the leadscrew dog clutch is useful for threading, it is definitely a useful and interesting accessory! Do you have information available on how you made one?

 

[eeler1]

And, besides, threading with the dial is kinda fun. Without it is not so fun.

 

[MetalMuncher]

And, besides, threading with the dial is kinda fun. Without it is not so fun.

I agree! When I bought my mini lathe several years ago, the very first thing I taught myself on it was how to single point turn threads, thanks to some great internet resources, and a good friend of mine who is a toolmaker by trade. Personally, I think the threading dial was a very cool invention. I can't imagine single point turning threads without it.

 

[machinistmarty]

If you thread much metric with an inch leadscrew, you will appreciate a thread chasing dial. Even using the method Conrad Hoffman suggests, You still have to wait on the lathe to reverse. After cutting threads for years with a chase dial, Its just too laborious to wait on a lathe to reverse its way out.

 

[higgite]

Whether or not the leadscrew dog clutch is useful for threading, it is definitely a useful and interesting accessory! Do you have information available on how you made one?

I'm not John, but here's a link to his web page with the info you're looking for:
http://www.gadgetbuilder.com/Dog_Clutch.html

Tom

 

[John Hasler]

The only way I can see that would work would require two contacts in series. One would be closed by a cam on the spindle and one by a (movable) cam on the leadscrew. You would turn the spindle by hand until the contact on it closed, and then adjust the cam on the leadscrew until that contact closed and the lamp came on. You would then do your threading, closing the halfnuts only when the light blinked on signaling that the spindle and leadscrew were back in the same phase relationship they were in last time the light blinked. I think I'd rather have a noisemaker go "ding", though.

Maybe I'll try this some day. Two microswitches, a battery, a couple of LEDs, a beeper, something for cams...

Ok, I tried it with a lashup of microswitches and clip leads. Works a treat. I did need to add a right-hand carriage stop to resolve the ambiguity when you close the halfnuts at a random spot.
I tried it out with 12 TPI, 11.5 TPI, and 9 TPI. I don't have the gears for metric.

I position the spindle so that both switches are closed and I hear the beeper/see the LED. I then position the carriage at my start point and close the halfnuts. I then position the right hand carriage stop to stop it there. I then start up the lathe and start threading. To start a pass I run the carriage to the right against the stop with the halfnuts open, wait for the beep and/or LED flash, and close the halfnuts. Works just like a threading dial but no need to remember whether to start on odd numbers, even numbers, full marks, half marks, etc.

I found myself anticipating the beep: I could tell when it was coming by the sound of the gears. Wouldn't want to rely on that, though.

 

[John Hasler]

Ok, I tried it with a lashup of microswitches and clip leads. Works a treat. I did need to add a right-hand carriage stop to resolve the ambiguity when you close the halfnuts at a random spot.
I tried it out with 12 TPI, 11.5 TPI, and 9 TPI. I don't have the gears for metric.

I position the spindle so that both switches are closed and I hear the beeper/see the LED. I then position the carriage at my start point and close the halfnuts. I then position the right hand carriage stop to stop it there. I then start up the lathe and start threading. To start a pass I run the carriage to the right against the stop with the halfnuts open, wait for the beep and/or LED flash, and close the halfnuts. Works just like a threading dial but no need to remember whether to start on odd numbers, even numbers, full marks, half marks, etc.

I found myself anticipating the beep: I could tell when it was coming by the sound of the gears. Wouldn't want to rely on that, though.

One of the cams needs to be movable.

 

[rick9345]

There are countless pages written on this subject that more than adequately explain threading,from "Machinery Handbook" to the "Atlas" and "South Bend" how to run a lathe.

 

[lawlessman]

If the thread you're cutting can be divided evenly by the pitch of the leadscrew I think you could engage the half nuts at any point. I could be wrong too......
[/QUOTEMy father was a master lathe hand, with over 50 years of hands-on experience. He taught me how to run a lathe, and had one simple rule for using the threading dial - here it is: When using the threading dial (and you should), for Even pitch threads, engage at any mark; odd pitch threads, engage at the same mark each time; metric threads, stop and reverse unless you have metric change gears. It has worked for me for years. If your dial doesn't have numbers, number it. Mine has 8 marks, every other one is numbered.
To avoid excessive wear on the gear that engages the lead screw, dis-engage the dial when not in use.

 

[rick9345]

Disengage? Probably not a very critical factor on a non load bearing gear spinning freely in a clean hobby type environment . Don't get hung up on minutia . It is hobby work/enjoyment.