# G0602 threading issues (not disengaging the half nut)



## GunsOfNavarone (Jun 22, 2019)

Hey all,
I have had my G0602z for over a year and finally have been playing with threading. Compound set at 29.5 degrees....threading tool is 60° and used a gauge to make sure it is set with work piece. Not backlash on my slides doing 12tpi on mild hot rolled 1/2" stock. My first scribe line looked good and I I did the reverse direction/ no disengage half nut. It seemed to be slightly scribing in two places right next to each other. My final product looked closed to metric 2.0 threads but we're very thin. Though there is no slop anywhere...there is on the leadscrew...but not how it connects to compound slide, but within the change gears. Lash adjustment is as tight as I can get it....but there is ample back and forth play within the gears. I'll post a picture of threads on a moment. Thoughts?


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## GunsOfNavarone (Jun 22, 2019)

Picture of thread


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## markba633csi (Jun 22, 2019)

Looks like something was moving during the cut- tool, toolpost, compound, leadscrew or even workpiece itself-  something was causing those two scribe lines and it isn't right, there should be only one, especially since you kept the half-nuts engaged
You are pulling the tool away from the work when reversing the carriage correct?


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## GunsOfNavarone (Jun 22, 2019)

I'm not gonna discount what your saying....but I've checked everything...it's all rock solid...it's just that leadscrew/change gears. It has a good 7 degrees of play. I feel like if be better to disengage half nut, pull away from work with compound. I know this is the less preferred technique, and I would really like to figure what's up with my lathe. This thing may have 4 or 5 hours of use on it and none threading.


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## benmychree (Jun 22, 2019)

It is not a good idea to pull out with the compound, it should be left at the same setting that the cut was taken on, pull out with the cross slide only. Start out with the cross feed handle at about the 10:00 or 11:00 position and the dial zeroed, and take each successive cut by feeding the compound in, however much you dare, you can take heavy cuts for the first several passes, then ease up for the finishing passes.  Some folks do the 29.5 deg thing, I do not, I set on 30 deg.  Hot rolled is not a nice thing to thread, it does not cut freely or finish nicely.  I would try disengaging the half nuts ands sucessively take trace cuts with not feeding in and see how the tool tracks on each cut, or rather does the tool track in the same location on the successive cuts.


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## DAT510 (Jun 22, 2019)

It looks like the angles of the two sides of the tread are not symmetric, which could be because your compound is set to 150.5 degrees vs 29.5,


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## darkzero (Jun 22, 2019)

That thread looks like the compound was not set at 29.5°. This happens a lot with people that have smaller asian import lathes. Commonly the compound scale on asian import lathes will read 0° & not 90°. If your scale reads 0° you have to set the compound to 60.5° to get the correct angle for flank threading. Typically the scale won't even read that far (only on lathes where the degree markings are on the cross slide) & you need to set it with a protractor, etc. My 12x36 is this way also, I made my own marks instead of having to use a protractor every time.

Edit: Well the scale should read 0° instead of 90°, what I should have said is that small import lathes usually don't have the additional scale directly on the cross slide like bigger lathes do.


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## benmychree (Jun 22, 2019)

Hold a 60 deg "fishtail" thread gage against the front side of the compound, it should appear to be 90 deg. to the ways.


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## fitterman1 (Jun 22, 2019)

Use your scribe line to verify your tpi.
First passes you can go slightly deeper.
Subsequent passes get shallower as you feed your crosslide in.
If you're leaving your halfnuts engaged, and reversing, then you must back off your crosslide a reasonable amount to clear your thread tops and then reset to depth for the following cut.
Make sure you remember last depth of cut, or write it down to help you.
Backlash in the geartrain can never be eliminated, we all have to wear this one.
Cheers alby


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## benmychree (Jun 22, 2019)

If you reset the cross slide to zero after pulling out at the end of each cut, and do not mess with the compound setting until ready for subsequent cuts, there is no need to remember or write down anything, you just feed the compound in a bit for each successive cut.


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## MontanaLon (Jun 23, 2019)

How are you holding the workpiece? In the chuck? Chuck and center? Between centers?

Your workpiece moved which isn't uncommon. Chuck not tight enough, or tight enough but inadequate engagement with the part.

Slap another piece between centers and see if you can cut a pretty thread. If you can then it eliminates all other possibilities but work movement.

If you had it in a chuck and with tailstock running a center did you inadvertently not lock the quill on the tailstock? I know if I don't lock mine just the weight of the handwheel knob will rotate it down to BDC and there is a bit of mechanical advantage with the threads. Granted, I have never seen it move anything it the chuck but I have seen it move and release tension on the center and with the tool pressure lead to a tapered cut.

Just spitballing, but I would lean toward the work moving in the chuck and try it again. But the tailstock losing pressure is within the realm of possibility too.


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## fitterman1 (Jun 23, 2019)

benmychree said:


> If you reset the cross slide to zero after pulling out at the end of each cut, and do not mess with the compound setting until ready for subsequent cuts, there is no need to remember or write down anything, you just feed the compound in a bit for each successive cut.


Why would i reset my crosslide to zero every time? Its the only thing telling my depth.
Oh i see, you swing your compound around and feed in with that.
My bad, i dont do that, i keep it normal and feed in with the crosslide.


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## GunsOfNavarone (Jun 23, 2019)

I really appreciate the info guys. I mis-spoke...I feed in with the coumpond, not the cross slide. I have tried to use between centers and also no tail suppport. I am using a 3 jaw...super tight and I can confirm my work is not shift. I did stay up last night researching...I did come across the Asian scale theory, I need to check that angle. 
this play i speak of can be felt the most when turning the spindle/chuck...changing directions (which being that I am reversing direction without disengaging, I feel like there could be something to this...that whole gear train has a lot of slop! I did try to to disengage the half nut and use the dial to drop in...being that I was doing 12 tpi,.I used different numbers on indicator (thought that was ok, my works was ALL OVER the place then. Seemed like every pass was somewhere new. I guess to keep it simple, i could try to thread at 60°. I new threading was difficult, this has just thrown it through the roof.


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## GunsOfNavarone (Jun 23, 2019)

markba633csi said:


> Looks like something was moving during the cut- tool, toolpost, compound, leadscrew or even workpiece itself-  something was causing those two scribe lines and it isn't right, there should be only one, especially since you kept the half-nuts engaged
> You are pulling the tool away from the work when reversing the carriage correct?


I am not pulling the work away when I reverse....should I? I am taking such light cuts, it's removing the stock so I feel it's just a light graze.


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## GunsOfNavarone (Jun 23, 2019)

benmychree said:


> It is not a good idea to pull out with the compound, it should be left at the same setting that the cut was taken on, pull out with the cross slide only. Start out with the cross feed handle at about the 10:00 or 11:00 position and the dial zeroed, and take each successive cut by feeding the compound in, however much you dare, you can take heavy cuts for the first several passes, then ease up for the finishing passes.  Some folks do the 29.5 deg thing, I do not, I set on 30 deg.  Hot rolled is not a nice thing to thread, it does not cut freely or finish nicely.  I would try disengaging the half nuts ands sucessively take trace cuts with not feeding in and see how the tool tracks on each cut, or rather does the tool track in the same location on the successive cuts.


Sorry, i meant cross slide...Compound is for feeding only.


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## GunsOfNavarone (Jun 23, 2019)

DAT510 said:


> It looks like the angles of the two sides of the tread are not symmetric, which could be because your compound is set to 150.5 degrees vs 29.5,


from my late night readings, this is starting to lead the pack in possibilities. I guess I am confused how I am to set it if my compound is off. If like to use my compound, but until I know what that is, am I trying to turn it 29.5° from being 90° perpendicular?


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## GunsOfNavarone (Jun 23, 2019)

darkzero said:


> That thread looks like the compound was not set at 29.5°. This happens a lot with people that have smaller asian import lathes. Commonly the compound scale on asian import lathes will read 0° & not 90°. If your scale reads 0° you have to set the compound to 60.5° to get the correct angle for flank threading. Typically the scale won't even read that far (only on lathes where the degree markings are on the cross slide) & you need to set it with a protractor, etc. My 12x36 is this way also, I made my own marks instead of having to use a protractor every time.
> 
> Edit: Well the scale should read 0° instead of 90°, what I should have said is that small import lathes usually don't have the additional scale directly on the cross slide like bigger lathes do.
> 
> ...


I couldn't explain my frustration if this is it. Bad enough I'm trying to learn...throw this curve ball at me....why would they do this?? (Rhetorical)


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## jcp (Jun 23, 2019)

GunsOfNavarone said:


> I am not pulling the work away when I reverse....should I? I am taking such light cuts, it's removing the stock so I feel it's just a light graze.


Retracting the tool with the cross slide at the end of the cut is mandatory.


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## Janderso (Jun 23, 2019)

Let us know what you find, that's an interesting thread you cut.


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## GunsOfNavarone (Jun 23, 2019)

benmychree said:


> Hold a 60 deg "fishtail" thread gage against the front side of the compound, it should appear to be 90 deg. to the ways.


So.....using that technique.....I end up with the compound at.......60.5° Perhaps this is why some people are running 60.5 and not having issues. I will run some more today and see....how ridiculous. I think you guys got this thing figured out without even breaking a sweat. I'll keep you posted. You saved me a lot of angry disassembly!


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## RJSakowski (Jun 23, 2019)

I have a 602 and the scale reads zero when the compound travel is parallel to the spindle axis.  If you elect to use the compound to in-feed when cutting, you need to set the compound to 60.5º to achieve the 29.5º feed angle.  Also, keep in mind that the divisions on the scale are actually 2.5º so you would set to just a bit past the 60º mark. 

There have been a number of discussions on this forum about this same problem. Once you get it figured out, I think you will find threading with the 602 to be simple.  Here is how I set mine up. https://www.hobby-machinist.com/threads/29-5-deg-angle-tool-for-lathe.34541/#post-299219


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## higgite (Jun 23, 2019)

GunsOfNavarone said:


> from my late night readings, this is starting to lead the pack in possibilities. I guess I am confused how I am to set it if my compound is off. If like to use my compound, but until I know what that is, am I trying to turn it 29.5° from being 90° perpendicular?


That is correct. But your problem has nothing to do with compound angle.


GunsOfNavarone said:


> I am not pulling the work away when I reverse....should I?


Yes, you should.


jcp said:


> Retracting the tool with the cross slide at the end of the cut is mandatory.


This ^^^. There is backlash in the gearing and lead screw, so simply reversing the direction of travel changes the timing between the spindle and the carriage. The track in one direction is offset from the track in the other direction by the amount of backlash in the system. When you reverse direction, the work turns a split second before the tool moves. That's why you saw two scribe marks on your first forward and reverse passes.


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## markba633csi (Jun 23, 2019)

Important point:  Whether you feed in with the compound or the cross slide (and you can do it either way) you MUST pull back the tool when you reverse because of the slop in the geartrain, that's what can ruin the thread. Most engine lathes have lots of play in the gears so you have to take that into account
Mark


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## GunsOfNavarone (Jun 23, 2019)

RJSakowski said:


> I have a 602 and the scale reads zero when the compound travel is parallel to the spindle axis.  If you elect to use the compound to in-feed when cutting, you need to set the compound to 60.5º to achieve the 29.5º feed angle.  Also, keep in mind that the divisions on the scale are actually 2.5º so you would set to just a bit past the 60º mark.
> 
> There have been a number of discussions on this forum about this same problem. Once you get it figured out, I think you will find threading with the 602 to be simple.  Here is how I set mine up. https://www.hobby-machinist.com/threads/29-5-deg-angle-tool-for-lathe.34541/#post-299219


RJ....I guess you don't know what you don't know. Had I read that thread earlier...would I have put the pieces together...I'm not sure. In hindsight, i see that I was coming in at such a "parallel" angle that any movement in was also a lot of movement left (on the threads) slowly thinning out the threads the "deeper" I went. I haven't even tried the new angle...but pretty sure it the culprit.
I have watched your builds on the 602 lathe for a while, even on another site which I believe is gone now. Your indispensable for info on making the 602 better. As I am learning the very basic and on, it's detrimental for the 602 to have things like this or the indicator dial being off, i will be working on your improvements in the future.


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## GunsOfNavarone (Jun 23, 2019)

higgite said:


> That is correct. But your problem has nothing to do with compound angle.
> 
> Yes, you should.
> 
> This ^^^. There is backlash in the gearing and lead screw, so simply reversing the direction of travel changes the timing between the spindle and the carriage. The track in one direction is offset from the track in the other direction by the amount of backlash in the system. When you reverse direction, the work turns a split second before the tool moves. That's why you saw two scribe marks on your first forward and reverse passes.


I'm pretty sure that flat angle has huge implications on the issue with that wacky thread...but yeah, there are other issues.
it makes sense to pull the work away when moving...that backlash will cause it to score at a different location, that will be changed now as well!


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## markba633csi (Jun 23, 2019)

It's like riding a bike, once you get it you'll say "how simple"!  It can get tedious though, making all those passes and focusing intently to not mess it up
Mark


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## GunsOfNavarone (Jun 23, 2019)

markba633csi said:


> It's like riding a bike, once you get it you'll say "how simple"!  It can get tedious though, making all those passes and focusing intently to not mess it up
> Mark


it's funny....Once things were going more as I expected....it was fun. Now, I'm not sure why screws/bolts don't cost $30 each and up, but whatever. Looking at these pictures, for the first (correct)attempt, I'm happy. Here is the next issue (Since RJ knows the gearing of the 602, this maybe easier for him to pull out his charts..
using the chart on the lathe, at 150rpm, using a 36 and 40 tooth gear(s) and the gear box on b/2...I'm supposed to have 12tpi...this looks more like 13 but not PERFECTLY, BUT MUCH CLOSER THAN 12. Thoughts on that?


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## GunsOfNavarone (Jun 23, 2019)

Here is completed (the previous 13tpi shot, I hadn't completed the thread depth yet)


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## GunsOfNavarone (Jun 23, 2019)

Janderso said:


> Let us know what you find, that's an interesting thread you cut.


it's make one hell of a barb....don't you think?


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## RJSakowski (Jun 23, 2019)

The threading chart on the 602 is correct.  You should have the 36 tooth gear in the a position and the 40 tooth gear in the b position.  The kobs should be in the II-B position.  The 120 tooth gear is not used for inch threads so the b gear should be engaging the 127 tooth gear.  If you are engaging the 120 tooth gear the thread pitch would be reduced by 120/127 which would mean the cut TPI would be 12.7 TPI instead of 12 TPI.


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## GunsOfNavarone (Jun 23, 2019)

I'm not home right now, but of that 2 gear stack (120 & 127) how to you pick which is engaged or how do you disengage one??


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## RJSakowski (Jun 23, 2019)

GunsOfNavarone said:


> I'm not home right now, but of that 2 gear stack (120 & 127) how to you pick which is engaged or how do you disengage one??



There is a spacer bushing which slides off the input shaft to the gear box.  The gear should be put on first, then the spacer.  If you had the lathe set up for metric threading or power feed, this arrangement would have been reversed.


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## GunsOfNavarone (Jun 23, 2019)

One thing leads to another....
I haven't played with this gearing setup...just the 2 small ones (40 & 36) looks like the keyway is broken...weird how the 127 tooth is connected to gears above and the 120 tooth is connected to transmission....what spacer? If I wanted to move small lower gear over to engage....it doesn't appear to move more in unless that is a spacer on that lowest shaft? Your saying for TPI I need to take out 127 tooth? As you can see, there will be gear engaging issues.


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## markba633csi (Jun 23, 2019)

Should be able to move that small lower gear in by swapping a spacer, or else you just flip it around


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## GunsOfNavarone (Jun 23, 2019)

Wow....figuring this out, can't believe this isn't covered in the manual. Need to loosen the ball oilers that is square...then shaft slides up/down on arm. The lower gear requires some massaging to get the shim off (that really could use a better bevel on it to get a gear puller or at least a flat edge to wedge in there)...I'll alter that a bit. The top shaft with the 120t will require something to shim that in, perhaps a very small gear that can't touch anything. Ordered a new keyway bushing to replace that shattered one, wonder how long that was like that.


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## GunsOfNavarone (Jun 23, 2019)

markba633csi said:


> Looking closely at the picture I think RJ is correct- 12.7 tpi-- just slightly coarser than 13


Yeah....that would make sense to what I'm seeing. Crazy how that was setup...have no idea if it came like that, never cut threads yet, i assumed it was set to power feed setup....I literally have a few hours on it. this has been quite the learning weekend!


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## markba633csi (Jun 23, 2019)

Yeah you pretty much have to check everything on these things- don't assume anything- but now you have a better understanding, more than if you just turn it on and use it
You may have to raid your junk box for washers and spacers or make what you need
I think it was set up to cut metric as you received it


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## RJSakowski (Jun 23, 2019)

GunsOfNavarone said:


> One thing leads to another....
> I haven't played with this gearing setup...just the 2 small ones (40 & 36) looks like the keyway is broken...weird how the 127 tooth is connected to gears above and the 120 tooth is connected to transmission....what spacer? If I wanted to move small lower gear over to engage....it doesn't appear to move more in unless that is a spacer on that lowest shaft? Your saying for TPI I need to take out 127 tooth? As you can see, there will be gear engaging issues.


OK, Sean, In the first photo the spacer is behind the gear.  The gear has to be pulled off and then the spacer can be removed.  The gear is then put back on the shaft followed by the the spacer, the washer, and the cap screw. The gear will then engage the 127 tooth gear.  In the third photo, the bushing is is broken and will need to be replaced.  It is P/N P0602715.  The 127 tooth gear also appears to be backwards.  The boss should face the tailstock  Also, you need a second gear, normally the 120 tooth gear, to keep the 127 tooth gear in place.  I have taken some pictures of my lathe and will send them later.  Mine was actually set up to cut 12TPI.   

Right now, I am being summoned to do a fish fry so I'll have to adjourn until later.


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## markba633csi (Jun 23, 2019)

mmm fish fry


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## RJSakowski (Jun 23, 2019)

markba633csi said:


> mmm fish fry


Walleye, deep fried, hash browns, peas, and cauliflower with mu.lti grain bread and a mug of beer.


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## GunsOfNavarone (Jun 24, 2019)

I have already ordered that part...I really can’t understand why it was shipped like that, I’ve only ever changed the smaller gears and just replicated everything else. It took some disassembly and scratching my head to figure out that oiler/nut/arm length adjustment...just really don’t understand why it’s not covered in the manual. I wonder how many other newbs have walked my path...I saw 120t and assumed I was going at it correct...but one gear was turning the top half and the other gear was turning the lower...it’s obvious now but I breezed it as I just assumed the factory setup was good.
Ugh.... thanks everybody!


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