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Tips/Techniques threading issues on CX 706

Tips/Techniques
6

6.5 Fan

Ultra Member
Premium Member
All the talk lately about threading had me wondering about the cx 706 lathe i bought. Tried to install the threading dial, no fit. The lead screw is 8tpi according to the manual, the gear on the bottom of the threading dial is a 40 tooth gear. It will kind of work with the very tip of the teeth on the gear catching on the lead screw but i can be certain that it will not be very accurate.
I sent trlvn a message as to his machine that he bought at the same time as i purchased mine. Also sent off an e mail to Busy Bee about the problem. This is the only problem i have had so far but have only made a few parts and hadn't got to threading yet. Anybody else run into this issue.
 
6.5 Fan said:
All the talk lately about threading had me wondering about the cx 706 lathe i bought. Tried to install the threading dial, no fit. The lead screw is 8tpi according to the manual, the gear on the bottom of the threading dial is a 40 tooth gear.
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I don't think you really have a threading dial there. I've never seen one that even remotely has that many teeth on it. Just guessing, I'd say more like 16 or so.

Can you post a photo?
 
I think that model needs lots of teeth on the dial so it can pass over the keyway. Threading and carriage feed are done by the same shaft. Maybe it has a gear for a 3mm pitch lead screw instead of the 8tpi one.

Screenshot_20230315_182016_Chrome.jpg
 
John Conroy said:
I think that model needs lots of teeth on the dial so it can pass over the keyway. Threading and carriage feed are done by the same shaft. Maybe it has a gear for a 3mm pitch lead screw instead of the 8tpi one.
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Wow, that's a monster thread dial! I could see that having a lot of teeth. Maybe even 40......

8tpi is 3.175 mm. 3mm is 8.45 tpi. That is pretty close. But maybe not close enough to engage. So ya, that's a possibility.
 
John Conroy said:
I think that model needs lots of teeth on the dial so it can pass over the keyway. Threading and carriage feed are done by the same shaft. Maybe it has a gear for a 3mm pitch lead screw instead of the 8tpi one.

View attachment 32300
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My little 10x22 lathe also has the keyway in the lead screw but it doesn't have a huge gear. I will try to remember to count them tommorow. My leadscrew is 16tpi and I believe only 9/16 maybe 3/4" in diameter.
 
Photos are a no go, phone and computer don't get along. :rolleyes: Just did a little measuring, the gear is 1.32" in dia. and 40 teeth. Lead screw is .77" dia. and 8tpi. Manual says T20x8tpi, the dial dia. is 1.17 so not huge.
Manual does not even mention using the thread dial, says to keep half nut engaged and reverse lathe to back up cutter. Precision Mathews says to use the dial for sae threads but not for metric threads, neither manual shows the thread dial and parts in the parts diagrams.
Looks like i will be leaving the half nuts engaged for both types of threads. Not how i learned and not how i run my Colchester, but i have never cut metric threads on the Colchester either. Hopefully you can teach an old grumpy guy new tricks.:)
 
6.5 Fan said:
Looks like i will be leaving the half nuts engaged for both types of threads. Not how i learned and not how i run my Colchester, but i have never cut metric threads on the Colchester either. Hopefully you can teach an old grumpy guy new tricks.:)
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That really sucks. Without a thread dial you can't even use the disengage and then backup method. You MUST NEVER disengage the half nut.

Frankly, I'd be very tempted to make a proper thread dial. The mounting holes are there. You just need to make gears that fit.

Might also be worth noodling out some other way of setting up when to engage the half nut.
 
6.5 Fan said:
Just did a little measuring, the gear is 1.32" in dia. and 40 teeth. Lead screw is .77" dia. and 8tpi. Manual says T20x8tpi, the dial dia. is 1.17 so not huge.
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My threading dial is about the same diameter and the gear on the indicator also measures about the same 1.32". I didn't count the "teeth" but I believe 40 would be about right. My lead screw is also approximately the same diameter as yours but mine is 16tpi.
 

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I converted to ELS on my CX706 so I don't use the indicator anymore, IIRC it has to be adjusted just right or it won't work and the adjustment is a bit finicky.
 
slow-poke said:
I converted to ELS on my CX706 so I don't use the indicator anymore, IIRC it has to be adjusted just right or it won't work and the adjustment is a bit finicky.
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Ya don't have the gear the tiniest bit misaligned if you power your keyway lead screw in reverse. Damn near wrecked things on mine by doing that once.
 
Dpittman your gear looks like it has the profile to fit a lead screw, mine is just a small flat face gear. I sent some pics to Busy Bee but don't expect a lot of help.
 
It's strange the Busy Bee manual doesn't even mention the threading dial, it says you must keep the half nuts engaged throughout the threading process. The Precision Matthews manual does have threading dial instructions for imperial threads and specifies an 8tpi lead screw and a 32 tooth threading dial gear. My friends CX706 has the correct 32 tooth gear on the threading dial. This is from the PM manual

Screenshot_20230327-024751_Drive.jpg
 
The PM manual is a lot more detailed than the BB manual. I counted the number of teeth several ties on my gear and got 40 every time. It will mot mesh with the 8tpi lead screw at all except for a very small portion of the gear.
I have a box of small gears kicking around, will have to see if i have a 32 tooth one tht could be fittind in place.
 
Got my CX706 a year ago (May 2022) and soon noticed the threading dial gear pitch was completely different from the lead screw it was supposed to engage. The threading dial gear was getting chewed up badly, so I pivoted it out of engagement with the lead screw to prevent damage to the lead screw. Complained to Busy Bee, and a new threading dial showed up in the mail a few days later. The new one fit much better. But I still leave it disengaged from the lead screw when not in use to prevent lead screw wear.

Also had a brush go bad in the motor, replaced under warranty, and it works "better than new" now, so clearly it was defective from the factory. Again, Busy Bee came good for it, not quick, but they were there with a solution.
 

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torx10 said:
Got my CX706 a year ago (May 2022) and soon noticed the threading dial gear pitch was completely different from the lead screw it was supposed to engage.
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You are not the first with this problem. How in the world do they manage to screw this up so badly so often!

It almost makes me think BB should do a recall!
 
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