opinions on feed idea

[shipto]

I have been thinking about thread cutting on my lathe for some time but the gears work out really expensive (and almost as rare as dragons teeth for my drummond)
so I thought tonight about a electronic feed system, basically you would have a bolt on sensor for the main shaft and a motor for the feed screw.
the sensor would send pulses to a control circuit which would then send pulses to the feed motor (the same as a usual cnc feed)
so in effect you could just program the feed to give you whatever feed ratio you needed, no more being restricted to the gear available.
does such a system exist already, if so links please and what are your thoughts on how accurate it would be?

[Weston Bye]

I did it. See this thread:
http://bbs.homeshopmachinist.net/showthread.php?t=42769

Absolutely dead-nuts accurate.

[shipto]

excellent work I never even concidered that it would be able to combine with milling as in #14.
May be contacting you for advice in the near future if you dont mind.

[macona]

http://www.autoartisans.com/ELS/

[Weston Bye]

... May be contacting you for advice in the near future if you dont mind.

I don't mind, drop me a PM when you're ready..

[djc]

Another really cheap option is TurboCNC. It will run on a DOS-based PC ($free); it costs $60 to register it. Unless you had the parts to hand, I don't think you could build Weston's system for this money.

[Weston Bye]

I don't think you could build Weston's system for this money.

Going back to the Original Post, I don't know that he would build "Weston's system" with the auxillary gearbox. His lathe probably has a geared head or at least back gears. The encoder would probably go somewhere upstream, rather than at the spindle.

So lets break it down:
Stepper motor, drive and power supply - the same for all systems.
Spindle zero sensor - same for all systems.

Other systems - breakout board or such.
My system - a handful of TTL chips, sockets, perfboard, terminals, thumbwheels. You have to put all these together - could be a big negative - but the money is about the same as a good quality breakout board.

My system - Encoder, about 60 bucks, or more, or less - it will depend on your installation.

Yeah, my system might be more costly, but not that much more.

Remember, my system is an electronic alternative to manual threading, nothing more - ever. If you want to add bells and whistles or migrate to CNC, take another path.

[shipto]

And of course with your system theres no need to have a pc attached.
Although I have been thinking things over and thought of upgrade for this, Again I am not sure if it already exists but here goes.
instead of one encoder and one stepper I am thinking two stepper motors with encoders built in (yes I know they are extremely expensive) one attached to the spindle and the other to the feed screw. this way you would have the option on smaller threads to just feed the tool in and have the spindle turn to suit the position.
Going as far as this however it may be easier to just go full cnc and have done with it.

[djc]

...Again I am not sure if it already exists but here goes.
instead of one encoder and one stepper I am thinking two stepper motors with encoders built in....

I am not sure it would work with steppers but it can and has been done with servos. See over in the main forum for a post on gear hobbing by Texas Tornado. Macona, I think, posted a youtube video of the concept.

[Weston Bye]

See this thread:
http://bbs.homeshopmachinist.net/showthread.php?t=32574
Look particularly at the second youtube video.
Steppers on everything except the tool post grinder.