Vevor Mini lathe

[Det2]

Well here's the question,
I have a small Vevor lathe. My issue is that I would like to use the auto feed for cutting some threads. Considering the MASSIVE power of this tool. I need to make multiple passes. Keeping it all in sync for second pass after stopping EXACTLY here is an issue.
I have tried to make something that would trigger the half nut but it is far less than accurate.
I'm thinking that there is a forward/off/reverse electrical switch that stops the whole lathe and reverses it. I SHOULD be able to hijack that signal and use an external switch mounted on the bed/carriage to either stop and or reverse everything so I keep everything in sync for a second pass.
Anyone got any experience with this? Or any thoughts as to why this won't work?
Thanks in advance.

b

 

[willf650]

I would doubt it would work as even if you stop it, it will continue to spin with no power so I don’t see how you would sync it.

Does this lathe not have a thread dial indicator? If not see if you can add it. Without it I don’t see how you’re cutting threads.

I don’t have a ton of experience but the indicator is how you’re supposed to sync the lead screw and engage it for subsequent passes. You’re not supposed to reverse rotation as the tooling will only cut in one direction.

 

[JuncleJohn]

The thread dial should keep your threading tool in sink with your previous passes. If threading up to a shoulder you can undercut a relief which will allow you time to stop before hitting the shoulder.

What you are proposing to do isn’t even a normal operation on a cnc lathe.

John

 

[Sumboodie]

What size lathe?
I have a mini lathe, 13x40.

 

[MushCreek]

I've cut threads on a lathe without a threading dial. It was a Hardinge tool room lathe. The one redeeming feature is that it has a quick retract on the compound. Still tricky. Any threading on a lathe will be multiple passes except in plastic. You set the compound at slightly less than 30 degrees. Once you're set, you don't touch the crossfeed dial; only the compound. Make a pass, shutting off the lathe and retracting the compound at the same time. With the compound retracted, run the lathe in reverse to get back out off the end of the part. Move the compound in a bit and repeat in forward. The half nut remains engaged the whole time. I've also seen people thread from the shoulder out, so you don't run the risk of running into the shoulder.

 

[RoninB4]

I need to make multiple passes.

-Single point threading on a lathe always requires multiple passes.

I have tried to make something that would trigger the half nut but it is far less than accurate.

-Some of the more expensive lathes have a kick-out that needs to set prior to threading, your lathe likely doesn't have this feature. If your lathe has a thread dial you'll need to follow the directions regarding engagement of the half nuts, the thread pitch usually dictates this.

I'm thinking that there is a forward/off/reverse electrical switch that stops the whole lathe and reverses it.

-Very often the thread dial is ignored and the half nuts are left engaged to ensure synchronization. The lathe is stopped, cross feed is backed out, the lathe is run in reverse (provided the chuck isn't threaded to the headstock) to clear the work, cross feed returned to "zero" and the next pass is started.

I SHOULD be able to hijack that signal and use an external switch mounted on the bed/carriage to either stop and or reverse everything so I keep everything in sync for a second pass.

-It is theoretically possible to "hijack" the signal but not likely that you'll be able to accomplish this as you want it to.

Anyone got any experience with this? Or any thoughts as to why this won't work?

-Thoughts? Your method would take a lot of time/expense for a tiny lathe, seems impractical. You can use an undercut, as previously suggested, if working up to a shoulder. If threading up to a shoulder seems risky (it can be) then perhaps you'll want to investigate flipping the cutter upside down, running the lathe in reverse (unless chuck is threaded to headstock) and threading from the undercut to the end of the workpiece. That way, there's no danger of running into anything.

Watch this for a better explanation. Joe Pie makes pretty good videos.

 

[txvwnut]

IYou set the compound at slightly less than 30 degrees. Once you're set, you don't touch the crossfeed dial; only the compound. Make a pass, shutting off the lathe and retracting the compound at the same time. With the compound retracted, run the lathe in reverse to get back out off the end of the part. Move the compound in a bit and repeat in forward. The half nut remains engaged the whole time. I've also seen people thread from the shoulder out, so you don't run the risk of running into the shoulder.

This right here. I would suggest doing the operation away from the chuck to avoid crashing the tool and the workpiece.

 

[Det2]

-Single point threading on a lathe always requires multiple passes.

-Some of the more expensive lathes have a kick-out that needs to set prior to threading, your lathe likely doesn't have this feature. If your lathe has a thread dial you'll need to follow the directions regarding engagement of the half nuts, the thread pitch usually dictates this.

-Very often the thread dial is ignored and the half nuts are left engaged to ensure synchronization. The lathe is stopped, cross feed is backed out, the lathe is run in reverse (provided the chuck isn't threaded to the headstock) to clear the work, cross feed returned to "zero" and the next pass is started.

-It is theoretically possible to "hijack" the signal but not likely that you'll be able to accomplish this as you want it to.

-Thoughts? Your method would take a lot of time/expense for a tiny lathe, seems impractical. You can use an undercut, as previously suggested, if working up to a shoulder. If threading up to a shoulder seems risky (it can be) then perhaps you'll want to investigate flipping the cutter upside down, running the lathe in reverse (unless chuck is threaded to headstock) and threading from the undercut to the end of the workpiece. That way, there's no danger of running into anything.

Watch this for a better explanation. Joe Pie makes pretty good videos.

Thank you for this. And for the thoughts! This is what I needed. Looks like I am going to abandon all hope of single point threading on this critter. My machine does not have that little threading dial. and it looks like that would be a real bother to add.
The signal hijack thing , at least for me, would be a no brainer my training and civilian job was in this sort of electronics. As one of my "hobbies" is dismembering stuff to see how it works, So I collect the useful parts. So I have bins of the parts, cost would be close to zero. Time, I'm retired. This is also a hobby, by design it's to fill the empty time and to learn. Most of the stuff I do is to see if I can. As such, I take it as a challenge when I'm told that can't be done. Mind you in a LOT of cases, I can't do it with what I have, but every so often. It can be done.
I try to work by the words of Robert Noyce : Do not be encumbered by past history. Go out and do something wonderful. Also the principals of Leo Yau : If I give you everything, of course you can do that, However, if I give you the bare minimum and you can do it, you have proven something about yourself. And for me, "It's only impossible because nobody has done it yet."

 

[MushCreek]

Don't give up! Just try threading away from the chuck. Run the spindle left hand and turn the tool upside down. Never disengage the half nut. Threading on a lathe is fun.

 

[RoninB4]

Thank you for this.

-You're welcome, glad to help

And for the thoughts! This is what I needed. Looks like I am going to abandon all hope of single point threading on this critter.

-You shouldn't give up threading if this would be something you'd want/need to do. There's a bit more to threading but, for me, it's a gratifying thing to do when I want/need better than what I have or what's available. Sometimes you want a fastener that's made of a better grade material (or a different material) than what's available in the hardware stores. Sometimes you get a shaft (machinery/automotive) that's got a partially bunged thread on the end, or a special nut that's been mangled. Single point threading on a lathe can make this possible and a whole lot less expensive (shafts) to do. It makes things possible rather than order/pay/wait for shipping. Just a suggestion.

My machine does not have that little threading dial. and it looks like that would be a real bother to add.

-The thread dial is handy but not always necessary. Once you get the change gears set you just leave the half nuts engaged and run the lathe in reverse like I've posted above. Usually about 6-7 passes (or less) can create a working thread in inch or metric with any thread pitch the gears are capable of making.

The signal hijack thing , at least for me, would be a no brainer my training and civilian job was in this sort of electronics.

-I won't doubt your knowledge but getting the motor to instantly stop doesn't take mass/momentum into account. Even if you get the cutter withdrawn (an additional problem) the inexpensive motor from Chi-Wan may not be able to handle instantaneous reversal. You would have better insight than I would. So even if it's possible for you it still doesn't seem to be a practical effort for the time/money it will take to accomplish this but that's entirely up to you. You could just thread away from the headstock (as in Joe Pie video) and still be capable of threading when you want to. I've been working in machine shops for 35+ years and single point threading, while fun, doesn't come up all that often. In my retirement shop at home I've only needed to single point thread a new component a couple of times for what was no longer available on the market.

As such, I take it as a challenge when I'm told that can't be done. Mind you in a LOT of cases, I can't do it with what I have, but every so often. It can be done.

-I get it, when someone tells me it can't be done I view it as "well then I can't lose by trying". I'm of the opinion that almost anything can be done if you throw enough time and money at the problem. The thing is....what do you actually have when finished? How often can I use it to make the time/money worth the effort? There's more than one path to the top of the mountain and many more lathes with better features for threading. For a short while I only had a crappy little lathe from Grizzly at home but still made that do what I wanted, including single point threading. Innovation is a terrific talent to have (when needed) but a work-around video is often available too for consideration. Not trying to discourage you, I do applaud your thought process for this. I am suggesting you save that creativity for a project you truly consider worthwhile. Only you can answer that question.

I try to work by the words of Robert Noyce : Do not be encumbered by past history. Go out and do something wonderful. Also the principals of Leo Yau : If I give you everything, of course you can do that, However, if I give you the bare minimum and you can do it, you have proven something about yourself. And for me, "It's only impossible because nobody has done it yet."

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Many of life's failures are people who did not realize how close they were to success when they gave up.

Thomas A. Edison