# Help with threading dial



## ddillman (Apr 17, 2021)

So I have an older Grizzly G1031 13 X40 lathe. I am not an expert but have had good luck threading. The thread dial has always been off a little bit. I start to close the half nut on one and it drops into place just after the line. So I decided to adjust it. I took the dial apart and there is a screw that holds the gear in place with friction holding the gear from turning. I locked the half nut down and set the dial on one. Tried threading a 5/8-11 thread. First pass was good measured 11Tpi. Second pass split the thread. tried several times always on the one. Works fine if I leave the half nut locked. I am feeding straight in. The lead screw is 4Tpi


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## Ken226 (Apr 17, 2021)

I'm not sure that I understand your question.    

Are you asking how to make minor adjustments to where the thread dial markings align with the index mark?   

One way is to pull the screw that attaches the dial to the carriage, and put a washer or spacer between the dial and carriage.   Adjust the thickness or number of spacers until it aligns the way you want.   

Adjusting the gear the way you did can work fine too.  But, if it's not a keyed or a press fit, you'll have to make sure it's secure and doesn't slip.   

When you say it's a friction fit, like tapered, held by screw pressure? 

As to the other issue,  So, are you saying that you removed the gear and reinstalled it in with a different positioning, and now the thread dial doesn't hit the same thread consistently?   If so, the gear is likely slipping on the shaft.

Disclaimer:  everything I typed above assumes I understood your questions correctly.


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## ddillman (Apr 17, 2021)

the gear is held by friction. it is not slipping. Yes I  disassembled and now it seems off. Almost like if you are cutting a metric thread where you have to leave the half nut engaged.


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## Ken226 (Apr 17, 2021)

If all that is correct,  then the gear tooth count to leadscrew pitch ratio is unchanged.  

The only thing that your modification changed was the alignment of the markings.  Adjust it until you get the alignment correct.

If it's the same gear and leadscrew as before,  and there gear isn't slipping, then it's fine.   Perhaps the misaligned index markings caused you to engage in the wrong spot.


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## benmychree (Apr 17, 2021)

With 11 TPI, you should be able to engage the half nuts on opposite numbered lines, like one or three or two and four, if you engage on any numbered line, you will split the lead.  With a thread as coarse as 11 TPI, you should be feeding in with the compound at 30 degrees to ease the chip load on the tool.


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## Ken226 (Apr 17, 2021)

benmychree said:


> With 11 TPI, you should be able to engage the half nuts on opposite numbered lines, like one or three or two and four, if you engage on any numbered line, you will split the lead.  With a thread as coarse as 11 TPI, you should be feeding in with the compound at 30 degrees to ease the chip load on the tool.


Exactly.


I was a little baffled by what he said.   

First he said
"Second pass split the thread. tried several times always on the one."  

  Assuming this to mean he engaged on #1 for each pass.

Then this
"the gear is held by friction. it is not slipping".


So, if the dial was engaged on #1 for each pass,   also was actually physically verified to NOT be slipping.  

That only leaves a few possibilities, like a sheared leadscrew pin, wrong size dial gear, slipping dial face,  wrong bi-focal prescription, or fundamental flaw in my understanding of physics.  

Any one of which is possible.


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## MyLilMule (Apr 18, 2021)

ddillman said:


> Almost like if you are cutting a metric thread where you have to leave the half nut engaged.


I have never heard of half engaging a half nut. This makes no sense to me at all.


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## BROCKWOOD (Apr 18, 2021)

I am just a beginner, but I do dabble in the English language some. I believe, as you indicate that there is no such thing as half engaging. Yet from the results posted, the point of engagement is off due to your readjustment of the dial. Given the dial is simply a reference point for proper engagement, it is possible to clock it to where it should be by simply hand rotating the spindle with an even number selected for your TPI & engage the threader (correct term please). You can calibrate it from there. It is my experience (with my Grizzly) that the dial has an infinite adjustability (set it wherever you want).


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## SLK001 (Apr 18, 2021)

When you engaged the half-nut on the other passes, what number did you use?

Here's a chart for SOUTH BEND lathes on using the threading dial.  If you use this, TEST IT FIRST to see if it is compatible with your lathe.


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## Video_man (Apr 18, 2021)

I have the same lathe.  The friction fit is apparently to prevent damage if there's a crash, letting the gear slip to protect it.  You have checked to see if the gear is loose; look for a damaged tooth that prevents full engagement with the lead screw, and then check for lateral movement in the lead screw.  If it moves left to right, check the thrust bearings.  You can adjust the gear on the indicator line by engaging the threading lever, engaging the slightly loosened dial gear with the lead screw, and turning the indictor to match the index line, then tightening the retaining screw on the gear.  FWIW I've found the lines on the indicator dial don't all line up exactly, and I re-marked a couple that didn't.  Not off by much, but enough for a rough engagement with the leadscrew.

/// EDIT ///  Out of curiosity, I ran a couple of 11 tpi threads, and like you, got split threads.  Positions 1-4 on the dial are supposed to be OK for that pitch, but I tried 1 and 3  on different parts (that is, 1 on one test and 3 on the other) and the thread split every time.  Never ran into this before.  It must be some design problem with that particular thread, I'm guessing, as in over 20 years with this lathe (bought new) I've never encountered this before.


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## ddillman (Apr 19, 2021)

just did some testing. chucked up some bolts this is what I got. 3/4-10 ok  5/8-11 no go unless you leave the half nut engaged
7/16 -14 ok  3/8-16 ok  I will just have to test whenever I do a different thread.


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## ddillman (Apr 19, 2021)

Video Man thanks for checking now I know I am not a complete idiot


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## ericc (Apr 19, 2021)

Uh oh.  Sounds like the wrong number of teeth on the gear.  It looks like something like this will happen if the dial is geared to turn too fast (too few teeth on the worm).  So it will only work with even numbers of threads.  What a drag.  I have never used the thread dial.  There is none on my home lathe, and the thread dial on the TechShop (maker space) lathe was not working.  At the TechShop, I used the reverse and never disengaged the half nuts.  Somebody said the sound of my threading makes me sound like a hobbyist who has no sense of working on the clock.  Best to ignore those sorts of comments; that person is just distracting.  Side note: in a community shop, do not distract the operator if he is in the middle of a cut.  It is not safe.  At home, I use the sharpie method of lining up three pen lines.


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## MyLilMule (Apr 19, 2021)

The number of gears on your threading dial should be related to the lead screw pitch. My 13" SBL is a 6 TPI lead screw, and the threading dial has 4 times that number of teeth, 24. So for every inch of carriage travel, my threading dial moves one whole number.

If that all matches up, then you may have a problem in your gearbox causing the labeled pitch to be incorrect.


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## Video_man (Apr 19, 2021)

There is something wonky with the gearing, apparently a design problem.  If you lock into one position, a la Metric threading, the pitch from one particular combination of quick-change levers (Q -Z) cuts an accurate pitch.  But that combination doesn't work with the thread dial.  There are four possible threads in Q-Z, 5 1/2, 11, 22 and 44.  None work with the dial but all if locked down will cut accurate TPI.  Two lathes, same model with same problem, it's something odd in the gearbox design.  I've cut many different threads on this lathe in other quick-change positions with no problem, so it must be limited to this particular group of settings.


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## rjs44032 (Apr 19, 2021)

Please let us know the number of teeth on the thread-dial worm-gear that meshes with the leadscrew. Also a pic of the dial itselft or how it's numbered. Then we can suggest how to proceed.

In previous examples, folks posted specs for typical thread dial with 4:1 worm-gear tooth count. If yours is different then you will have limitations.

Best Regards,
Bob


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## Video_man (Apr 19, 2021)

rjs44032 said:


> Please let us know the number of teeth on the thread-dial worm-gear that meshes with the leadscrew. Also a pic of the dial itselft or how it's numbered. Then we can suggest how to proceed.
> 
> In previous examples, folks posted specs for typical thread dial with 4:1 worm-gear tooth count. If yours is different then you will have limitations.
> 
> ...


Thank you for your interest, please see the attached image.  I think the problem is not with the thread dial, as every other thread except in one particular quick-change setting works perfectly well.  Oddly, as I mentioned, if the thread dial is not used, the pitches cut are accurate from this same problematic qc setting.


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## Video_man (Apr 19, 2021)

Here is the entire threading chart.


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## ddillman (Apr 19, 2021)

Yes it has to be something with that particular quick change gear setting


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## ddillman (Apr 19, 2021)

Problem solved


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## MyLilMule (Apr 20, 2021)

Not unlocking the half nut and running the lathe in reverse is the "solution" to any TPI. You overcame the challenge, but you did not solve the problem.


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## rjs44032 (Apr 20, 2021)

Video_man said:


> Thank you for your interest, please see the attached image.  I think the problem is not with the thread dial, as every other thread except in one particular quick-change setting works perfectly well.  Oddly, as I mentioned, if the thread dial is not used, the pitches cut are accurate from this same problematic qc setting.
> 
> 
> 
> ...



Video_man, Sorry I got called into work shortly after I posted.

Your thread dial is a bit different from mine but still usable for all imperial threads. You have 4 times the number to teeth on the worm wheel. So you should be able to use it as standard, except for the dashes being odd numbers on the dial. So you could think of the odd numbers on the dial as dashes.


For any even thread engage on any number.
For any odd thread engage on any odd number.
For any 1/2 thread engage on 1 or 5
For 1/4 threads engage on 1
Using this method, you can engage on any odd number for a 5/8-11 thread. You should not have to keep the half-nuts engaged. If that does not work then there is something mechanically wrong. Or the gearing is not set up correctly for that thread. Hope this helps.

Best Regards,
Bob


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## Video_man (Apr 20, 2021)

Thanks for your input, Bob.  Actually, though some anomaly in the design, it doesn't work on this lathe in the "Z" selections.  However, on a hunch, I tried using the unmarked dial positions halfway between 2 and 3 and the opposite position 6-7, and found that the 5 1/2, 11 and 22 threads tracked the dial perfectly.  Didn't try the 44 thread but assume the same.  But, a solution at last.  Thanks to everyone who replied.


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## rjs44032 (Apr 20, 2021)

Video_man said:


> Thanks for your input, Bob.  Actually, though some anomaly in the design, it doesn't work on this lathe in the "Z" selections.  However, on a hunch, I tried using the unmarked dial positions halfway between 2 and 3 and the opposite position 6-7, and found that the 5 1/2, 11 and 22 threads tracked the dial perfectly.  Didn't try the 44 thread but assume the same.  But, a solution at last.  Thanks to everyone who replied.


Great!. Glad you got it worked out.

Best Regards,
Bob


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