Who Needs A Thread Chasing Dial?

[Franko]

I've ordered a new PM lathe, and it doesn't come stock with a thread chasing dial.

I'm wondering why I would want one. I've cut several dozen good successful threads on my old lathe, and though it has a thread dial, but I've never used it. Partly, because I don't really understand it.

I've watched 30 minute uTube videos by guys who sure seemed to understand every aspect of thread chasing, as well as every tooth on every gear in their machines., not to mention every turn on their lead screws. A couple of them commented that a machinist using a thread dial can cut twice as many threads with a dial that a machinist not using one. That makes me deduce that thread chasing dials are good for production work, but I don't see why.

I'm willing to be convinced to purchase and use a thread chasing dial, but I don't see how there are less steps with a dial as opposed to reversing out and forwarding back in. You have to back the bit out and back in plus advance both ways.

 

[stupoty]

I havnt got a brake on my lathe so coasting to a stop each pass might be fun

I did set my vfd to stop very quickly one day and the chuck unscrewd a little but thats another story.

Stuart

 

[GK1918]

Just my thoughts that reversing only creates more wear on half nuts. I made my own chasing dial.
So what I do is to engauge half nut by hand (motor off) then where it engages I mark the dial with
a sharpie and use that mark every time so I have no concern what the books says -odds & evens-
lines & numbers . to each his own but thats my way. As far as being "speedy" when returning
the carrage just watch the dial bringing the dial a little before the witness mark.then close the
half nut. Just like playing in a band, you aquire a rythem In high school we had a program
early release to go out in the real world. So being a gear head I chose Textile plant. I got to
operate 10 massive Crompton Knowles weaving machines built in 1933. You bet to get a
rythem real fast. The massive shuttle travels about 60mph back and forth. Again playin in
a band perfect timing >to stop you throw the clutch apply brakes< Kid next to me didn't
have the drum beat, just like a lathe crash the shuttle flew out and took out the line
forman to the hospitol he went, not only "we call a smash" which is ripping a million
ends (think of threads) means that machines down for a month. all in your timing..
ah memories
sam

 

[darkzero]

I do & I wouldn't want to be without one. A thread dial makes threading much easier & quicker. I hate threading using the stop the spindle & reverse method, such a waste of time IMO. My lathe has an imperial leadscrew so that is how I had to thread metric pitches & because of which I avoided metric threading as much as I could. That is until I learned about Conrad Hoffman's method for metric threading. Now I don't mind single pointing metric threads on my lathe.

Often I use very short thread reliefs, like .05"-.07" which doubles as an oring groove. I also often thread without a thread relief. I also make parts with internal threads leaving only .01"-.015" from the end of the thread to the bottom of the bore with no thread relief. Without a thread dial allowing me to disengage & reengage the half nuts on point I wouldn't be able to thread so close to a shoulder. I don't have a VFD or clutch on my lathe, by simply turning off the spindle during threading I still have to wait for the spindle to coast to a stop as Stuart mentioned. Before I learned about the method I mentioned, when threading metric close to a shoulder, I would have to use my foot brake & I didn't like doing that.

Probably not a need for most people but without a thread dial I wouldn't be able to single point multi start threads either. I don't often need to thread multi start threads but I have needed to.

 

[pineyfolks]

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......

 

[Mark_f]

I didn't have a thread dial when I got my lathe and threading was NOT fun. It was tedious and very time consuming. Now that I have a thread dial, I actually enjoy threading. It is much easier and faster plus I feel all that running back and forth with the half nuts engaged will wear them out.

 

[george wilson]

In one of my English published lathe books,I can't recall which,alternatives to not having a thread dial were listed. One I recall was to have a contact at the tail end of the lathe. Every time the lead screw revolved,it would blink on a light bulb. The operator would close the half nuts exactly when the light blinked. That way,he was closing the half nuts in the same place in the leadscrew's rotation. You can cut ANY thread,odd or even #,if you close the half nuts on the same revolution spot every time.

I might find it distracting to have a light beeping on and off all the time I was cutting a thread. Maybe a very small light? I'd more likely find a small gear that meshed with the lead screw and make myself a thread dial.

 

[brino]

Partly, because I don't really understand it.

Hi Franko,

To be able to put the cutting tool back in the same groove to take another deeper cut you need a way to have the cutting tool synchronized to the rotation of the work. Leaving the half-nut engaged is certainly one option. If that works for you and meets all of your needs then happy threading! I believe the benefit of using a threading dial is only in speed, which in a hobby shop may not be a priority.....

However, understanding another technique will sometimes come in useful. For me, I may not recall all the details, but at least I am aware there are some to look up. My biggest problems are: i) seemingly very limited number of grey cells for storage, and ii) what little stays in my memory is not accessed often enough to make those paths nimble......if I do not do an operation for a while it gets a little "foggy". As for the why and how of the threading dial here's how I think of it.......

If you think about the half-nut (with the lathe off) if you do dis-engage it and move the carriage exactly one lead-screw thread to either side, you would then be able to engage the half-nut again, but the tool point will be one lead-screw pitch off from where it was. Obviously that could mess with a second pass (depending on the screw pitch being cut).

The threading dial just gives you an indication of how the lathe spindle and tool were synchronized for the first pass. If you use that same position for each subsequent pass then you do not need to leave the half-nut engaged. This means you can return the carriage to the "start" of the next pass by hand, and not throw the machine into reverse and wait for the (thread cutting slow) feed to bring it back.

I never even try to remember all the details about cutting a thread that's a multiple of the lead screw you can engage the feed lever when the threading dial is on any line.......or is it any numbered line?, or any even numbered line? .....except in February that has only 28 days, but every four years it's 29.......

I simple note the exact number on the dial for my first pass, and always go back to exactly that number for subsequent passes.....it's just easier on my brain.

All the cautions above and complications of cutting metric on an imperial machine still apply.

-brino

 

[4GSR]

My luck would be: First thread needing to cut, a 1/2-13 UNC. Single point without a thread dial? At 325 RPM? Won't happen in my shop!

Get the thread dial!!! You will thank us later for doing so.

 

[4GSR]

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