CX701 gearbox questions

[PaulL]

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

 

[Tom O]

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.

 

[Susquatch]

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

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.

 

[PaulL]

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!

 

[Susquatch]

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!

 

[Susquatch]

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.

 

[PaulL]

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 ;-)

 

[Susquatch]

@plalonde - time and practice will be your friend.

 

[Six O Two]

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

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.

 

[PaulL]

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.

 

[Darren]

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

 

[PaulL]

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.

 

[Six O Two]

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?

 

[phaxtris]

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

 

[PaulL]

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.

 

[phaxtris]

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

Easy fix then !

 

[Susquatch]

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.)

 

[PaulL]

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.)

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.

 

[Susquatch]

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.

 

[PaulL]

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.