# CX701 gearbox questions



## PaulL (Mar 22, 2022)

Hi, I just got my first lathe - a new CX701 lathe from Busy Bee.  I'm mostly loving it, but the three gearbox levers are very jammy.  A few questions that the manual doesn't seem to answer:
- Should I be changing my speeds with the spindle running or with the machine stopped?  How do the gears mate/select?  I guess I could take it apart to find out, but I'd rather not.
- Relatedly, can I change from forward carriage travel to reverse carriage travel without stopping the lathe?  For metric screw cutting it's annoying to turn off the machine each pass to move that lever.  So I expect that you can change it live, but I'd hate to mess up my transmission.
- Should I be selecting lead screw vs carriage travel running or stopped?
- Is there a way to lock the spindle?  


Turning an adapter for the QCTP is turning out to be a really fun first machining project - the Slow Change TP is definitely showing it's deficiencies.

Thanks,
  Paul


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## Tom O (Mar 22, 2022)

I’d rather stop the lathe as I think most will the bigger lathes might have synchromesh or something but with square cut gears I wouldn’t take the chance unless the manual states otherwise. What does BB say I would think they would know.


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## Susquatch (Mar 22, 2022)

plalonde said:


> Hi, I just got my first lathe - a new CX701 lathe from Busy Bee.  I'm mostly loving it, but the three gearbox levers are very jammy.  A few questions that the manual doesn't seem to answer:
> - Should I be changing my speeds with the spindle running or with the machine stopped?  How do the gears mate/select?  I guess I could take it apart to find out, but I'd rather not.
> - Relatedly, can I change from forward carriage travel to reverse carriage travel without stopping the lathe?  For metric screw cutting it's annoying to turn off the machine each pass to move that lever.  So I expect that you can change it live, but I'd hate to mess up my transmission.
> - Should I be selecting lead screw vs carriage travel running or stopped?
> ...



Welcome from Farmland South of Chatham Ontario! 

Hey, I'm no Busy Bee CX701 Expert. Maybe one of those chaps can chime in. 

But, unless your equipment has clutches and syncros or a direct drive variable speed motor, changing gears while running is a BAD IDEA! 

Sometimes the gears won't easily engage because they interfere. Don't force them. Just turn the chuck by hand until they release or engage.


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## PaulL (Mar 22, 2022)

Tom - Thanks. I should have thought of asking BB directly.  Drafting the email now.
Susquatch - Turn the chuck!  D'Oh, I was grabbing the feed shaft or threading screw to give them a wiggle. Much messier and harder to grip than the chuck.

Thanks!


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## Susquatch (Mar 22, 2022)

plalonde said:


> Much messier and harder to grip than the chuck.



You can also insert the chuck key and use that as a Lever to help turn it in the lower gears. 

Or make a special key just for the purpose. Add a spring so you don't accidentally leave it in the chuck. That's really bad news too!


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## Susquatch (Mar 22, 2022)

Oh yes, and about reversing the chuck for threading:

You can do metric threading with the threading dial but always use the same mark. 

Just disengage the half nut as you normally would, then stop the lathe, then back off the compound with the lathe off, then put it in reverse and engage the half nut at the same mark on the way out. Let it wind its way past the thread start, stop the lathe, reset the cross slide, and advance the compound. Works like a charm.


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## PaulL (Mar 24, 2022)

I dare say there's a ton of ways for threading to go sideways!  On my 4th try on this little post to hold my QCTP, which has inch threads on one end (for the tool post nut) and metric on the other (the mounting hole in the compound).  I thought the slow-change tool post was a hassle, but the extremely-slow-change change gears are the real bear!
I have made the metric end successfully once, at least, before messing it up on inch end ;-)


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## Susquatch (Mar 24, 2022)

@plalonde - time and practice will be your friend.


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## Six O Two (Mar 24, 2022)

plalonde said:


> Hi, I just got my first lathe - a new CX701 lathe from Busy Bee.  I'm mostly loving it, but the three gearbox levers are very jammy.  A few questions that the manual doesn't seem to answer:
> - Should I be changing my speeds with the spindle running or with the machine stopped?  How do the gears mate/select?  I guess I could take it apart to find out, but I'd rather not.
> - Relatedly, can I change from forward carriage travel to reverse carriage travel without stopping the lathe?  For metric screw cutting it's annoying to turn off the machine each pass to move that lever.  So I expect that you can change it live, but I'd hate to mess up my transmission.
> - Should I be selecting lead screw vs carriage travel running or stopped?
> ...



With variable digital speed, you can change it while it's running. Feeds and feed direction should only be changed with the machine stopped. You should be able to change from lead screw to carriage travel while running. Essentially, any of these knobs should only be changed when the machine is stopped.





Anything on the carriage can be changed with it running.


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## PaulL (Mar 24, 2022)

Thanks Marco - that makes sense looking at the expanded diagram.
Now to work out my real mystery.  The A/B/C selection is off by a factor of two from the tpi indicated on the threading chart, for at least one set of gears (9/18/36).  I get 9 where I should get 18, 18 where I should get 36, and 36 never ;-). I'll probably try another change gear set and see if it's persistent.  Then it's tech support. 
The ratios look right when feeding however.


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## Darren (Mar 24, 2022)

There is a lever for selecting threading or feeding.  The RH lever in the above photo.


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## PaulL (Mar 24, 2022)

Yes, and it works - but when threading my ratio is off.  Something in the A/B/C section of the gearbox isn't going right.  I'm walking the parts diagram now trying to figure out the total gear ratio between the banjo and the lead screw.


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## Six O Two (Mar 24, 2022)

plalonde said:


> Now to work out my real mystery.  The A/B/C selection is off by a factor of two from the tpi indicated on the threading chart, for at least one set of gears (9/18/36).



I can't speak to this particular machine, but when I bought my ct089, the gear threading chart included in the manual had some wrong entries for gear ratios. I ended up searching online and found a different threading chart for a similar machine whose values were correct... so... that might be an issue for you too. Maybe look at threading charts for similar machines or call tech support?


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## phaxtris (Mar 24, 2022)

In regards to the threading being double

I would assume you have at least one change gear, maybe it's loose, maybe it's mounted on one of the studs with another gear, is it possible you just don't have the correct change gear setup. The southbend 9a I had would do exactly what you are describing if you have the the two change gears mixed up


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## PaulL (Mar 24, 2022)

phaxtris said:


> In regards to the threading being double
> 
> I would assume you have at least one change gear, maybe it's loose, maybe it's mounted on one of the studs with another gear, is it possible you just don't have the correct change gear setup. The southbend 9a I had would do exactly what you are describing if you have the the two change gears mixed up


I think you nailed it. I was reading the diagram exactly backwards.


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## phaxtris (Mar 24, 2022)

plalonde said:


> I think you nailed it. I was reading the diagram exactly backwards.



Easy fix then !


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## Susquatch (Mar 24, 2022)

Six O Two said:


> I ended up searching online and found a different threading chart for a similar machine whose values were correct...



I know you solved your issue. But I'd like to comment on your post above. 

I found that the chart that was on my lathe as well as the one in the manual were both incomplete.  I made my own chart by going through every possible gear combination and found many missing TPI and many missing metric threads that are all valid threads mentioned in various technical references. A few of them were even very common threads. 

I highly recommend that anyone who has a lathe do the same. It also helps generate a better understanding of how it all works. 

As a side benefit, I now know how to cut a new gear if and when I ever did need to cut a thread that my lathe does not support - although I don't know what that would be...... Perhaps I should be proactive and figure that out before hand. Another task for the priority list. (Insert big sigh here.)


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## PaulL (Mar 24, 2022)

Susquatch said:


> I know you solved your issue. But I'd like to comment on your post above.
> 
> I found that the chart that was on my lathe as well as the one in the manual were both incomplete.  I made my own chart by going through every possible gear combination and found many missing TPI and many missing metric threads that are all valid threads mentioned in various technical references. A few of them were even very common threads.
> 
> ...


Yes, I spent a dull meeting this afternoon noodling with gear ratios and the chart from my lathe, along with the transmission diagrams and understand the machine a lot better now.  

The A/B/C lever gives 1:1, 2:1, and 1:2 respectively by selecting a 16, 24, or 32 tooth gear.  Which is darned near enough excuse for me to open the transmission and figure out how/why it's doubling the 24 to make that sequence work out.  Those exploded diagrams make it really hard to see what's driving what.

But the good news is that I cut the needed 18tpi thread. The bad news is that I blew the other end of the part.
5th try tomorrow.  I'm a slow but throrough learner.


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## Susquatch (Mar 25, 2022)

plalonde said:


> But the good news is that I cut the needed 18tpi thread. The bad news is that I blew the other end of the part.
> 5th try tomorrow. I'm a slow



Ya, it's not easy deciphering those drawings sometimes! 

Any idea why you keep blowing a thread? What happens when it blows? Maybe I (we) can help.


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## PaulL (Mar 25, 2022)

Susquatch said:


> Ya, it's not easy deciphering those drawings sometimes!
> 
> Any idea why you keep blowing a thread? What happens when it blows? Maybe I (we) can help.


It's mostly a matter of learning and getting used to the machine - I have to do 4-5 operations perfectly, including 3 change gear sets to get this silly post done.  One set for carriage advance, one set for 18tpi, and another set for metric 1.5mm.

On the first thread I cut I discovered the angle gauge on my compound is 90 degrees out of phase with the manual I was following, so cut a pile of staircases.  That's fixed now, I know what the setup should look like.  Part to scrap bin.

On the second part I cut a poor thread, and then realized I didn't have a good way to hold the piece to turn the other end to diameter without messing up my newly cut threads.  And by realized, I mean after damaging the theads trying to hold it there.  New order of operations: Turn the long shaft and thread the end of it 18tpi, then reverse it in the lathe and cut the short metric end.  Part to scrap bin.

On the third part, I cut 9ish tpi on that end instead of 18, see bad reading of manual.  Part to scrap bin.

On the fourth part, I over-shot my diameter.  Maybe not enough to scrap the part (5 thou), though I expect I won't be happy with it.  I'll continue with it to finish debugging this process.  I overshot, I suspect, by being innattentive on depth-of-cut-is-radius and dial-is-diameter-read.  Or else I did something boneheaded on my last pass.  In either case, I now have a pad of paper and pencil by the lathe to jot down my numbers instead of keeping them in my head.  I can certainly see the appeal and utility of a DRO, though I'm the kind of stubborn that will learn to do it with dials reliably before I go the DRO route.  Long winded way to say, Part to scrap bin.

I'll try to finish the 4th part today, for the practice, and cut number 5.  I think I'm going to cut my larger diameter, turn it around in a 4-jaw to recenter, cut my small diameter, pull the part, change gears and *test* on some conveniently sized scraps I now happen to have lying around, cut the 18tpi on the end of the small diameter, change the gears to metric 1.5mm pitch, *test* on some other conveniently sized scap, turn the work around and hold it in the 4 jaw on the unthreaded part of the shaft, and cut.  At least this pulls some pieces from the scrap bin for better utility ;-)

I'm looking forward to being able to work this out in my head instead instead of in front of the lathe.


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## phaxtris (Mar 25, 2022)

You could turn it between centers, you won't mess up the threads on either end by re chucking, and everything would end up concentric without having to dial it in on a 4 jaw


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## PaulL (Mar 25, 2022)

phaxtris said:


> You could turn it between centers, you won't mess up the threads on either end by re chucking, and everything would end up concentric without having to dial it in on a 4 jaw


I was thinking about that, but I worry that my dog might lose contact with the drive pin when I stop the spindle, which I've seen happen the my first (and only) try at turning between centers (to true up my tail stock).  This seems like another way to spoil the work, though a bit of discipline I could make sure the dog was in contact with the drive pin before each threading pass.


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## phaxtris (Mar 25, 2022)

plalonde said:


> I was thinking about that, but I worry that my dog might lose contact with the drive pin when I stop the spindle, which I've seen happen the my first (and only) try at turning between centers (to true up my tail stock).  This seems like another way to spoil the work, though a bit of discipline I could make sure the dog was in contact with the drive pin before each threading pass.



You could wire the dog to the drive pin with tie wire, or tack it, if you have a welder


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## YYCHM (Mar 25, 2022)

What's the run out on your 3J?


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## Susquatch (Mar 25, 2022)

plalonde said:


> It's mostly a matter of learning and getting used to the machine - I have to do 4-5 operations perfectly, including 3 change gear sets to get this silly post done.  One set for carriage advance, one set for 18tpi, and another set for metric 1.5mm.
> 
> On the first thread I cut I discovered the angle gauge on my compound is 90 degrees out of phase with the manual I was following, so cut a pile of staircases.  That's fixed now, I know what the setup should look like.  Part to scrap bin.
> 
> ...



It is clear to me that you think of yourself as a beginner. But you are really doing quite well. My read of your excellent desciption of what is happening goes like this. 

1. Your shaft is plenty long enough to be able to chuck your part in the 3 jaw. Any run-out on the chuck is unlikely to be bad enough to cause a problem on what is probably a 1/2 or 5/8 shaft (I don't recall what you said it was). In any event, you can keep re-clocking the shaft to get the best runout possible when you swap ends. Also, if you cut the big end first, the runout on the small end will get partly consumed by the size change. Whatever runout there is left won't matter when the part is installed. 

The thread on your metric end is short enough to be able to chuck the part on the shaft and not damage the thread on either end. Just push the thread into the spindle further than the Jaws reach. If I am misunderstanding, you can always chuck right onto the threads by making a sleeve out of a pop can to protect them. 

ALWAYS use a thread gauge on a very very light threading cut to check the thread pitch after that first light pass. If it's wrong, you change the settings, put dykem on the part and try again. Doesn't matter how sure you are. Check it anyway until it's right. 

I trust you are only using the cross slide to back the threading tool out and return it to the same place. Threads can be cut with a plunge cut using the cross slide, but it's not good practice. The depth of cut is set using the compound which is set at 29.5 degrees to cut on the leading edge of the threading tool. You must use geometry to calculate the advance required to cut to the right diameter. (or use trial and error) 

I hope that helps a bit. 

If not, send me a pm with your phone number and I'll call you and walk you through it. 

Once you get your head around the process, I promise it will become easy. I enjoy threading. Perhaps more than any other standard lathe activity.


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## PaulL (Mar 25, 2022)

phaxtris said:


> You could wire the dog to the drive pin with tie wire, or tack it, if you have a welder


That's the kind of thinking I come here for.  Yeah, tie wire is the perfect solution to keeping these in sync.  I'll try it.


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## Susquatch (Mar 25, 2022)

plalonde said:


> That's the kind of thinking I come here for.  Yeah, tie wire is the perfect solution to keeping these in sync.  I'll try it.


I'll be honest, I really don't like this approach. As the thread cut gets deeper the load on the wire and dog will increase which could allow the part to rotate and skew the thread. As I said above, I really doubt your three jaw is out enough to screw up your threading and what little there is can be accomodated by cutting the bigger shaft end and thread first.

That's not to say that a dog won't work, just that it's something else to go wrong and it is not needed to do good work for your application.


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## PaulL (Mar 25, 2022)

YYCHM said:


> What's the run out on your 3J?


I've gotten to about 4 thou on a part I put back in.  It's probably good enough for this project, but given I get to less than 5 tenths when I set it up in the 4-jaw...  If only it was less painful to switch the bolt-on chucks.  For some obnoxious (cough *cost*) reason they included only 3 studs to hold the chuck base plate to the spindle, so I also have to move the studs across every time I change over.  Getting faster at it, but also more frequently just chucking straight up in the four-jaw.


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## PaulL (Mar 25, 2022)

Susquatch said:


> It is clear to me that you think of yourself as a beginner. But you are really doing quite well. My read of your excellent desciption of what is happening goes like this.


Thanks. 


Susquatch said:


> ALWAYS use a thread gauge on a very very light threading cut to check the thread pitch after that first light pass. If it's wrong, you change the settings, put dykem on the part and try again. Doesn't matter how sure you are. Check it anyway until it's right.


That's one I've learned now.  I think I'm still too heavy-handed on the touching-off so my test passes feel like they are leaving too much mess.  But I think that's explained by your next point:


Susquatch said:


> I trust you are only using the cross slide to back the threading tool out and return it to the same place. Threads can be cut with a plunge cut using the cross slide, but it's not good practice. The depth of cut is set using the compound which is set at 29.5 degrees to cut on the leading edge of the threading tool. You must use geometry to calculate the advance required to cut to the right diameter. (or use trial and error)


I was trying to "simplify" my process and drop the compound out of the equation, and I see now from your description how I can return the cross-slide reliably to the same spot, separating depth of cut from position of slide by using the compound.  That makes sense of the more complex setup that I screwed up early on.  Separating the actions will reduce the error potential.  Thanks.


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## phaxtris (Mar 25, 2022)

Susquatch said:


> I'll be honest, I really don't like this approach. As the thread cut gets deeper the load on the wire and dog will increase which could allow the part to rotate and skew the thread. As I said above, I really doubt your three jaw is out enough to screw up your threading and what little there is can be accomodate by cutting the bigger shaft end and thread first.
> 
> That's not to say that a dog won't work, just that it's something else to go wrong and it is not needed to do good work for your application.



But the load would be on the pin not the wire, the wire would just keep the pin in contact with the dog if he were to reverse the spindle. 

I was thinking about this more Im not sure that it would even matter, someone correct me if I am wrong here, but the spindle is directly connect via gear reduction to the lead screw, say you reverse the spindle to ok go backwards, the dog slams to the other side the the pin, no biggy your not cutting anything yet, you run the lathe forward to continue cutting your threads, the dog slams back to the other side, everything should still be in time, you just have ~355 degrees of backlash to take up, I don't believe threading between centers is some Voodoo magic...I'm sure that's how they did it before Chuck's were a thing


But everyone is right Realistically the run out of his 3 jaw isn't a big deal for this application, it was just an idea and maybe a learning project


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## PaulL (Mar 25, 2022)

phaxtris said:


> the dog slams back to the other side, everything should still be in time, you just have ~355 degrees of backlash to take up, I don't believe threading between centers is some Voodoo magic...I'm sure that's how they did it before Chuck's were a thing


Yes, thinking of it as 355 degrees of backlash makes sense.  My concern was that as I start turning, I often wind up "turning" but without the dog picking up yet - I had enough friction in the spindle-end center to drive the work without the dog, though not enough to drive while cutting, so I can see the cut starting with a judder and a slip as the dog engages.  



phaxtris said:


> But everyone is right Realistically the run out of his 3 jaw isn't a big deal for this application, it was just an idea and maybe a learning project


I agree on the learning opporutnity - there's a lot to learn here!


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## PeterT (Mar 25, 2022)

Holding a threading die in the tailstock may not be as accurate as one might think either. There a few sources of potential error creep & if they collectively stack in one direction, make for less than ideal threads. You may not notice it as much on larger threads but could on smaller/finer pitch:

- tailstock position relative to spindle axis. Hopefully you check this often but they can drift, which then moves the die relative to part rotating axis & cuts the threads unequally on the shaft. Most commonly TS can drift in/out over time. But someone posted a review video of brand new BB hobby lathe where quill center was high by 6 thou. He was under the impression this was to account for future bed wear. Nope, sorry, that 100% QC problem. He rectified by resurfacing base & got it to within 1/2-thou, much better.

- die in die holder. Most dies have some sort of adjustability so they can cut slightly tighter/looser threads. Die holders account for this by slightly looser ID. But that means the OD is no longer circular so when die holder retention set screws are engaged, another source of off-axis. This isn't a problem when hand threading because the die self-centers. But on a lathe setup in TS you have now locked this axis.

- die holder. Some of the aftermarket barrels are so-so quality. There's the barrel, which slides on a shaft, which may be held in a chuck or integrated into MT taper. I think runout would be pretty low, but you get what I mean, a thou here, a thou there....

As the shaft OD increases & material gets tougher, dies start requiring a lot of gronk because its a lot of material to cut even though that's what dies are designed to do. You may find the shaft starts slipping in the chuck & other issues. If you're making a batch of parts, best thing you can do is set up for threading, then rinse & repeat swapping the parts in, thus preserving your compound angle setup & depth of cut etc.


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## Susquatch (Mar 25, 2022)

phaxtris said:


> But the load would be on the pin not the wire, the wire would just keep the pin in contact with the dog if he were to reverse the spindle.
> 
> I was thinking about this more Im not sure that it would even matter, someone correct me if I am wrong here, but the spindle is directly connect via gear reduction to the lead screw, say you reverse the spindle to ok go backwards, the dog slams to the other side the the pin, no biggy your not cutting anything yet, you run the lathe forward to continue cutting your threads, the dog slams back to the other side, everything should still be in time, you just have ~355 degrees of backlash to take up, I don't believe threading between centers is some Voodoo magic...I'm sure that's how they did it before Chuck's were a thing
> 
> ...



Jezz, I sure hope I didn't come across as dogs = voodoo magic! LOL! 

I only wanted to point out that there is a reason everyone uses chucks nowadays for most operations instead of dogs. Dogs are not fool proof especially when things are already complicated.  Anyway, that decision is just a choice, all the methods discussed will work. 

Perhaps I am also biased by the fact that I just finished making a tool post bolt the same as the OP is making. My choice was to use a collet chuck for the job but if I didn't have that, I would have used my 3 jaw and the end result would have been the same. 

Glad you figured out the tool geometry, that should be a huge help making a good thread. For this job, you could set the compound for 30 degrees instead of 29.5 and it would work fine. The purpose of using 29.5 is just to keep the secondary surface (the one the tool slides along) clean with a slight 1/2 degree cleanup on the right side of the tool tip while the left side does all the work. 

I find that most people cutting threads for the first time get confused by all this 29.5 degree complexity. But it sounds like you noodled it out. But just in case, just think about cutting a 60 degree thread by coming in at a 30 degree angle (half of 60) and using the left side of the tool to cut progressively further into the thread. Then twist the compound another half a degree to keep cleaning up the right side a teeny tiny wee bit too. It becomes second nature in no time. 

Lastly, don't worry about how messy those test cuts look on the surface. Just keep them shallow. Use dykem on previous cuts just to hide them until you are happy. You don't even need to change the compound one iota while testing. The new threads will show up in the dykem. 

I am also a bit surprised you are not screaming like a wild banshee about cutting metric threads. They are not so easy. If you are cutting metric threads as easily as imperial ones. I AM IMPRESSED! 

If not, then search this forum for metric threads using a thread dial. It's way easier that stopping the lathe perfectly each time. Or we can set up a call.


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## PaulL (Mar 25, 2022)

I just took an hour in the shop out of my workday to give this another go.  My test nut goes on the 18tpi end, and in a couple of hours I'll get to go back out and turn it around and get the metric end sorted.  Lots of space to hold onto the shaft without damaging the threads.  Used the cross-slide only to engage/disengage, which meant I could keep bringing it back to my dialed-in zero, and the compound to from the thread, letting me inch forward by a couple of thou at a time, reliably.  I'm not convinced my thead forms are perfect (they seem a little asymmetric), and the gutter at the end of the threaded section is a bit rough, but I'll take it!  





Thanks for all the feedback!


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## PaulL (Mar 25, 2022)

Susquatch said:


> If not, then search this forum for metric threads using a thread dial. It's way easier that stopping the lathe perfectly each time. Or we can set up a call.


If I understand the thread dial correctly, doing metric with it should come down to just always starting on the "1" rather than trusting any of the other partitions of the screw, right?  Mine is numbered 1-4, so I assume each numbered position corresponds to engaging the 0th, 2nd, 4th, and 6th "position" of the 8tpi screw within each inch modulus. Inch modulus is meaningless to metric, so just be consistent and start on the same thread modulus each time, from within 1" of travel of the point where the thread starts.

Or will that lead me grossly astray?  I'm going to try it on a piece of scrap and see where I wind up.  

The hard part with this end is that I don't have a test nut - the nut is under my tool post, and I'm not liking the idea of breaking down my setup to test the threads.  I guess I'll have to do the actual math on it.


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## PaulL (Mar 25, 2022)

YYCHM said:


> Wowa... Too much stick out.  Was the narrow end supported by a center in tailstock?  Looks like the piece spun in the chuck?


I had tail support in that I pulled out so I could get the nut over - you can see the center in the end.  

And now you get my confession - yes, I had a bad moment part way through the threading.  I managed to dial my cross-slide in one turn too far during one cut, and stalled the lathe and budged my toolpost.  I think my tail support gave out, I may have not locked the tailstock correctly. I didn't notice that the work had turned in the chuck, about 1/6th of a turn: 








There was a bunch of tooth-gnashing and careful re-alignment of the tool in the thread on the right mark of the threading dial.  If I'd noticed it had rotated in the chuck I'm not sure I'd have tried to fix it!


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## RobinHood (Mar 25, 2022)

plalonde said:


> Or will that lead me grossly astray? I'm going to try it on a piece of scrap and see where I wind up.


It might very well.

I presume your lathe is Imperial. For Metric threads, engage the half nut lever and leave it engaged throughout the whole metric threading operation. Use spindle reverse to move the carriage back to the starting point. You can not use the threading dial when threading in the “off units” system to which the lathe lead screw was made.


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## RobinHood (Mar 25, 2022)

plalonde said:


> If I'd noticed it had rotated in the chuck I'm not sure I'd have tried to fix it!


It happens. Perhaps a little above what you can do at this time, but there are ways to “chase” an existing thread and salvage the part.

Look at this video from Joe Pie (there are others as well). He explains how to chase a thread.


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## Susquatch (Mar 25, 2022)

@plalonde - please allow me to explain that again. 

I deleted my previous post after redoing it here.

About metric threading. No, it isn't as simple as choosing only the number one. It actually doesn't matter what number you choose as long as you never change it. However, for metric threads it's a bit more complicated. 

Most references will tell you that you should never disengage the half nut at all when threading in metric. That way it's always in the same place so thread indexing is never lost. It's not about always using the same number, it's about never disengaging it! It must stay exactly where it was for all cutting passes. But I find this too difficult to do. It also requires a very large thread relief.

I accomplish the same thing by disengaging it when I reach the relief, letting the thread dial move however much it moves (but never more than one turn) and then putting it back where it belongs when that setting comes back when I reverse.

The process goes like this:

Take your first pass with the half nut engaged at the location of your choosing. For discussion purposes, let's say we choose position 2.

When the relief is reached, disengage the half nut. The cutting tool will stop moving, but the threading dial will start moving until you shut off the lathe. Shut off the lathe .

When the lathe has stopped, turn the cross slide out one full turn on the handle. Then put the lathe into reverse.

Watch the threading dial. As soon as it comes around to the number 2 (or whatever you chose), engage it again. If you miss, don't wait wait for it to go around again. That will not work. Instead, put the lathe in forward until it passes the mark, and then try again. The goal is to put it back exactly where it was. Not one turn more or less. Exactly where it was. This is the same as having left it engaged but without the stress of missing the thread relief.

After it is back where it was on the threading dial, you leave the lathe in reverse until the carriage is back before the start of the thread ready for another pass.

At that point, you stop the lathe, crank the cross slide in one turn to zero, advance the compound a reasonable amount (say 10 or 15 thou), and put the lathe in forward to cut another pass.

About your slip. For most cross slides and most thread sizes, one full turn is enough to clear the threads. I like to set my zero with the crank handle facing down. That way I can crank it out one turn to down again, dial a bit on the compound, and then crank it in one turn to zero. One turn is hard to overdo or underdo. But you can also tell just looking at the tool as it approaches the part that you are off and stop the lathe in time.

About the fit. If you have thread wires, there are charts that list the optimum diameters for all thread sizes. You don't really need a test nut. Just use the wires to measure the threads.

If you don't have wires, make some. But instead of using the charts, use your old bolt and duplicate that measurement on the new bolt with the same wires.

Then go get some thread wires or a threading Micrometer when you have time.


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## PeterT (Mar 25, 2022)

This link is useful for thread sizes & provides input/output for wire measurement sizes. There is a metric version in there somewhere as well.
Disclosure: I am from the thread mic owners fraternity. As opposed to, once again I dropped a fr*cken wire in the chip pan fraternity






						UN imperial screw thread calculator
					






					theoreticalmachinist.com


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## PeterT (Mar 25, 2022)

Tom Lipton metric threading demo & article link he refers to
http://conradhoffman.com/metricthreading.htm


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## PaulL (Mar 26, 2022)

And success!  I have made a part!










Thanks particularly to Susquash who spent a while with me going over screw threads and the screw dial. I was close, but he closed the gap.

I'm not at all pleased with my surface finish - it's off the first tool that I've ground myself, and it's, um, sub-par.  Works for this piece which is hidden from view.

I did learn a new way to screw up metric threads on my lathe however.  The instructions are clear: leave the half-nut engaged, stop the motor at the end of the cut, back out your tool, put the motor in reverse, and engage the motor to get back to the start.
Note that it says "put the motor in reverse".  It does not say "put the feed screw in reverse".  But what could be the harm?  The feed screw lever feels better in-hand than the awful motor direction switch (which I'm going to have to replace with something nice).  So what happens? As you move it you sometimes change which tooth in the gearbox gets engaged, shifting the carriage just a hair.  But sometimes not!  Most times not! Which led me to believe it was fine, until it missed and gouged my threads up. 
Lesson learned: leave the *whole* transmission engaged when cutting metric threads.  Or at least have a perfectly repeatable way to get the exact same teeth all along whenever you want to move your carriage.

Another fun bit - thanks to RobinHood for the link to chasing threads.  I had to do it once - my first fit of the tool post thread was too tight.  I had marked alignment of the part relative to the chuck, but of course I needed to reset the tool in the thread.  Easy as pie - between the cross-slide and the compound I was able to adjust the tool to just kiss the right hand face of the thread.  I was able then to advance my spindle by hand to make sure I was tracking right, and got off another couple of thou to a perfect fit.


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## Susquatch (Mar 26, 2022)

No worries, you did great! Ya, a few mistakes along the way but a mistake isn't a mistake unless you don't learn something from it. You learned plenty and prolly way faster than you would have without them. 

Finish is its own art. Tool type and shape (a whole course of its own), surface speed, feed/cutting depth, material (both cutting tip and part), etc etc etc etc etc all affect surface finish. 

For threads, the four most important things are a sharp tool, the right tool, the right speed, and to get the 29.5 degree compound advance angle right. 

For math guys like you, the way to look at the 29.5 is to realize that it is designed to shave the right side of the thread groove just a hair to keep it smooth while the main left edge does the majority of the cutting. 

Well done! 

What did you end up doing to get the thread depth right?


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## PaulL (Mar 26, 2022)

Susquatch said:


> Well done!


Thanks, and thanks for the help.


Susquatch said:


> What did you end up doing to get the thread depth right?


I did it the worst possible way.  I eyeballed "close" - I knew the tops of the threads would basically come off, and I'd be almost at form.  Then I tore down my setup, pulled the tool post and test-fitted, found it tight, then put everything back and chased the thread back on.  I'd left myself an extra half-inch of theaded space to cut off when I finished, so I had some nice sacrificial threads to test the setup with.  Second try fit perfectly, nice and snug.


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## 6.5 Fan (Mar 26, 2022)

Just take practice.......lots of practice. Glad you got it figured, next part you work on finish.


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## PaulL (Apr 9, 2022)

Following up on my QCTP install - it's working well, except that it's *just* marginal for the height of my compound - with 1/2 tools I wind up 20 thou over center.  So there was only one thing to do.  Today's fun was chucking them up in the 4-jaw and taking 50 thou off the bottoms.  I could probably have taken as much as 125 without affecting function.  No more problem centering.


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## PeterT (Apr 9, 2022)

You did well. Some people fight with that if they are hardened very much. 

Usually why this happens is people buy the tool post size based on lathe swing specified in catalogs. But the critical dimension is top of compound to spindle axis & some import lathes are quite a bit higher by comparison.


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## PaulL (Apr 9, 2022)

PeterT said:


> You did well. Some people fight with that if they are hardened very much.
> 
> Usually why this happens is people buy the tool post size based on lathe swing specified in catalogs. But the critical dimension is top of compound to spindle axis & some import lathes are quite a bit higher by comparison.


I followed the recommendation of the tech at BB.  I don't regret the purchase, but the service is a bit off.


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## YYCHM (Apr 9, 2022)

plalonde said:


> I followed the recommendation of the tech at BB.  I don't regret the purchase, but the service is a bit off.



You got Accusize stuff at BB?


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## PaulL (Apr 9, 2022)

PeterT said:


> You did well. Some people fight with that if they are hardened very much.


I did break a few inserts until I figured out depth of cut and speed.


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## YYCHM (Apr 9, 2022)

plalonde said:


> I did break a few inserts until I figured out depth of cut and speed.



Carbide inserts and interrupted cuts do not play well together.  HSS is a better choice in those situations.


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## PaulL (Apr 9, 2022)

YYCHM said:


> You got Accusize stuff at BB?


They call it BB4037 (iirc).  I assume it comes down to what they can source.


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## PaulL (Apr 9, 2022)

YYCHM said:


> Carbide inserts and interrupted cuts do not play well together.  HSS is a better choice in those situations.


Now you tell me!


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## YYCHM (Apr 9, 2022)

plalonde said:


> They call it BB4037 (iirc).  I assume it comes down to what they can source.











						QUICK CHANGE TOOL POST 6 12 SWING
					

Busy Bee Tools is Canada's largest Woodworking & Metalworking retailer. Find power tools, woodworking tools & metalworking tools at factory direct prices.




					www.busybeetools.com
				




I'll be darned..... I'm going to have to go to BB  and check this out.  Accusize eh....... Same price as on Amazon.


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## Susquatch (Apr 9, 2022)

plalonde said:


> Following up on my QCTP install - it's working well, except that it's *just* marginal for the height of my compound - with 1/2 tools I wind up 20 thou over center.  So there was only one thing to do.  Today's fun was chucking them up in the 4-jaw and taking 50 thou off the bottoms.  I could probably have taken as much as 125 without affecting function.  No more problem centering.
> View attachment 22947



I recently helped another member deal with this same problem on his BB lathe. His compound is cast iron and has a raised section on it that the tool post sits on. We simply milled off a tenth of an inch from the compound. That way any new tool holders he buys will all fit just fine and he doesn't need to worry about turning down all his tool holders or any hardness issues. 

We were also careful to assess the remaining thickness of the compound to make sure it wasn't weakened by cutting it down excessively. 

It all turned out really well.


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## PaulL (Apr 9, 2022)

Susquatch said:


> I recently helped another member deal with this same problem on his BB lathe. His compound is cast iron and has a raised section on it that the tool post sits on. We simply milled off a tenth of an inch from the compound. That way any new tool holders he buys will all fit just fine and he doesn't need to worry about turning down all his tool holders or any hardness issues.
> 
> We were also careful to assess the remaining thickness of the compound to make sure it wasn't weakened by cutting it down excessively.
> 
> It all turned out really well.


Yes, mine has the same step.  I contemplated the same fix, but I'm not brave enough to swing my whole compound slide on the face plate.  Until then, I'll keep taking smaller bites.
today I even went looking for some aluminium to try milling up some more holders, but Metal Supermarkets has decided to close Saturdays now due to staffing shortages.  Which is, of course, the only day I can get out there given the day job.


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## YYCHM (Apr 9, 2022)

plalonde said:


> today I even went looking for some aluminium to try milling up some more holders, but Metal Supermarkets has decided to close Saturdays now due to staffing shortages.  Which is, of course, the only day I can get out there given the day job.



Dovetail tool holders on a lathe?  This should be interesting......


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## PaulL (Apr 10, 2022)

YYCHM said:


> Tool holders on a lathe?  This should be interesting......


There's so many threaded holes in them, I'm pretty sure I can set them up in the T-slots of my cross-slide.  so it comes down to figuring out a collet for the end mills.


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## Susquatch (Apr 10, 2022)

plalonde said:


> Yes, mine has the same step.  I contemplated the same fix, but I'm not brave enough to swing my whole compound slide on the face plate.  Until then, I'll keep taking smaller bites.
> today I even went looking for some aluminium to try milling up some more holders, but Metal Supermarkets has decided to close Saturdays now due to staffing shortages.  Which is, of course, the only day I can get out there given the day job.



Surely you know someone with a mill......

Although shipping would prolly be required, you can certainly send it to me. I'll happily do it for you. 

The good news is that your modified holders will still fit! 

Lastly, don't be afraid of mounting the cross slide in your 4 jaw. Only a rough balance is required. And the back surface is plenty flat enough to mount it properly on the jaw flats or the chuck face. You only need to take a tenth off and that can be done slowly using a hss tool facing off 10 thou at a time. By using hss, you can cut slowly and the interrupted cut isn't that big a deal. 

The real problem is mounting a cutting tool without a compound and tool holder...... LOL!


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## PaulL (Apr 10, 2022)

Has anyone figured out why the compound has that step on these lathes?  I'm guessing it's an attempt to get more meat for the threads that hold the tool post.
I'll likely take mine apart today to measure the clearance between the feed screw and the casting, just to satisfy my curiosity.


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## PaulL (Apr 10, 2022)

Susquatch said:


> The real problem is mounting a cutting tool without a compound and tool holder...... LOL!


These tool holders sure look like I could hold them down to the cross slide using strap clamps and shims...
But not today ;-)


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## Susquatch (Apr 10, 2022)

plalonde said:


> Has anyone figured out why the compound has that step on these lathes?  I'm guessing it's an attempt to get more meat for the threads that hold the tool post.
> I'll likely take mine apart today to measure the clearance between the feed screw and the casting, just to satisfy my curiosity.



It is done so an AXA tool post fits it properly.  The lathe is on the small side for a BXA holder. It's not that it won't work, but the BXA is designed for a bigger lathe and bigger tools. The AXA is right sized for that lathe and without the platform it isn't high enough. The BXA is for bigger lathes and need to sit lower. 

The tool post bolt is just recessed a small amount into the compound along with a keeper set screw to maintain the indexing.

When you think about how the compound is mounted, any extra meat for strength should be at the back not the front. Since the back has no extra meat, it's obvious the front doesn't need it either. So it's only about height not strength.


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## Susquatch (Apr 10, 2022)

plalonde said:


> These tool holders sure look like I could hold them down to the cross slide using strap clamps and shims...
> But not today ;-)



Ya, I wouldn't do that either. Wanna send it to me? If so I'll pm you my address. Turn around would be about one week. 3 days (or less) on each end for the courier and 1 hour on my end for milling.


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## PaulL (Apr 10, 2022)

Susquatch said:


> It is done so an AXA tool post fits it properly.  The lathe is on the small side for a BXA holder. It's not that it won't work, but the BXA is designed for a bigger lathe and bigger tools. The AXA is right sized for that lathe and without the platform it isn't high enough. The BXA is for bigger lathes and need to sit lower.


That doesn't explain why the lathe is a bit small for the AXA holder I have, then.  Unless they think I should only be going up to 3/8" tooling.
But the knurling tool is pretty marginal at its height.  
I don't regret the purchase, but I wish they hadn't cheaped out on the last .250" to make it a true 12" swing instead of 11.75"


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## PaulL (Apr 10, 2022)

Susquatch said:


> Ya, I wouldn't do that either. Wanna send it to me? If so I'll pm you my address. Turn around would be about one week. 3 days (or less) on each end for the courier and 1 hour on my end for milling.


I think I'm good for now, but thanks for the offer.  I might take you up on it in June when I go away on holidays - I don't want to be without the tool for a week right now while I'm in the fun part of the learning curve.


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## Susquatch (Apr 10, 2022)

plalonde said:


> I think I'm good for now, but thanks for the offer.  I might take you up on it in June when I go away on holidays - I don't want to be without the tool for a week right now while I'm in the fun part of the learning curve.



Ya, totally understand. Whenever. But if there is someone closer with a mill, a visit to them would have you up and running right away! 

And ya, an AXA is normally for 3/8 tooling not 1/2.  

You will want to get a pinch type knurler if you want to do knurling. They are MUCH easier to use than the push type.


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## DPittman (Apr 10, 2022)

One of the first things I did with my then new 10x22 lathe was to chuck the top part of the compound in the 4 jaw and turn that step off. I still ended up milling down a couple of tool holder some so I could hold some 3/8 tool bits


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