Who Needs A Thread Chasing Dial?

[GadgetBuilder]

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

 

[Doubleeboy]

I can't believe someone selling a NEW lathe without a thread dial today. Just unheard of today.

yup, what 4gsr said. Sounds like a kit lathe to me, makes ya wonder if it comes with a tailstock, or maybe that is extra too. Even a HF mini lathe comes with a thread dial.

michael

 

[RJSakowski]

Years ago, when I first started threading with my 6" Atlas, I didn't use the thread dial. No manual for my lathe and no internet to go to in those days. The belt tightener lever was easily available and I never threaded to a shoulder so it worked....sort of.

My Grizzly G0602 does not have a clutch or any other way to quickly stop the spindle so the only recourse is to disengage the half nuts (I suppose that I could thread outward by reversing the spindle rotation and inverting the cutting tool or cutting from the backside). I started using the thread dial and would not go back to the old method again.

BTW, the Ox Tool video linked by Will in post #4 is an excellent demo of cutting metric threads with an inch leadscrew using the thread dial.

 

[f350ca]

Does the lathe you ordered have a metric pitch lead screw? If so I don't think a thread dial would work.

Greg

 

[Franko]

Greg, it says it has a NCH PITCH main lead screw.

Maybe I should have said, but I've posted it all over the place and didn't think which lathe was of importance. I figured this would be a good discussion of the advantage of using a thread chasing dial on any lathe.

The lathe I ordered is Matt's new model PM 1228-VF-LB. For the most part it is identical to the PM1127, but with a D1-4 chuck, a lead screw clutch and a 2HP brushless DC motor — and it is an inch longer. Don't bother looking for it on the internet, even on Quality Machine's web site, it can't be found. If you are interested, I've posted the spec sheets in the PM 1228-VF-LB thread. I think there is a photo of it near the first post.

Thanks so much for all the thoughtful comments. It has been illuminating.

So, I'm seeing that one of the main advantages of a thread chasing dial is that you can disengage the half-nut for a faster stop at or near the shoulder, rather than stopping the motor and letting it spin down. That's a valid point. I've always cut threads by killing the motor ahead of the shoulder and hand turning the chuck to the end of the thread. That wouldn't work if the half-nut is disengaged.

I don't know that I have enough nerve to run a tool all the way to a shoulder under power feed. My new lathe's lowest speed is 50 rpm, so that may not be as scary as the much higher low speed on the lathe I have. I've seen videos where people cut threads by hand turning the chuck and not using the motor except to back out.

One question: I see mention of a "clutch" in several replies. By clutch, are you referring to an emergency brake, or the clutch on the lead screw, or some other clutch?

I don't find it that unnerving that a lathe would be sold without a thread chasing dial. I've noticed that a lot of high end lathes don't even come with a chuck, because it is high end and experienced machinists may have different needs and preferences on chucks. I've noticed that when I've purchased a package of accessories that I end up replacing most of the items at some point.

I'm not completely sure the 1228 doesn't come with a dial. I don't see one on the photograph and it isn't mentioned in the description.

 

[John Hasler]

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.

John

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...

 

[eeler1]

Bingo, easier threading to shoulder, faster threading speeds, immediate stop of the tool advancing, don't have to power down, reverse, power down, and advance again.. For 95% of threads, the dial makes life way easier and faster. Plus, as others noted, less lead screw wear. That's about it. But, suit yourself.

 

[brino]

Thanks so much for all the thoughtful comments. It has been illuminating.

Agreed! Franko thanks for the great topic; everyone else thanks for the great discussion.
Very enjoyable!

 

[Tony Wells]

If there weren't advantages or benefits, they wouldn't exist.
I wouldn't thread without one. On larger lathes, stopping and reversing the spindle can be quite a hassle. I understand about Metric threading, of course, but if I got into doing it regularly, I'd have a dedicated machine. In fact, I may just do that. I have a spare lathe.

 

[planeflyer21]

As stated above, it is hard to believe that lathes can come without a threading dial these days. Even the cheapest mini-lathes have them.

I would ask "Why do the big production lathes all have threading dials? What benefits does a production shop gain from having them installed?"

Quicker time between passes, less scrapping of parts, less crashing of machines, it works forward or reverse, for right- and left-hand threads, internal or external threading, whether cutting from the front or back of the work piece.

Does the lathe you ordered have a metric pitch lead screw? If so I don't think a thread dial would work.

Greg

You can find lots of information online about the difference between metric and imperial/inch threading dials, lathes equipped with the incorrect dial, the number of teeth per gear on each, etc.