Threading with carbide inserts

So these VFD systems you guys talk about. Do they kill all power to the lathe when the carriage reaches the stop?
 
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mikey said:
Gotta' admit that the electronic stop is slicker than owl do-do! Unfortunately, you need a VFD with braking resistors so us poor guys with non-VFD set ups are left in the dust. Mark, you are the man!
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Stopping my lathe quickly is not an option. I thought about using a proximity sensor linked to a solenoid to disengage the half-nut. I think that would work fine if I got the mechanical linkage right.
Robert
 
rwm said:
I thought about using a proximity sensor linked to a solenoid to disengage the half-nut. I think that would work fine if I got the mechanical linkage right.
Robert
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The link below shows a purely mechanical means of the same. Too bad it wouldn't work both for turning and threading.

 
On the 1024 I do not disengage the halfnuts. Once I determined the stopping point during the set up I will cut the relief with the threading tool to the thread depth. From that point on, the operation is just like threading metric, half nuts are engaged until finished l.
 
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I do single-pass full-depth threading all the time, using a 16ER G60 insert at low (80-200) RPM
The threads aren't as pretty as the pictured above, of course, and it helps to clean them up with a die or a thread file.
 
Here's a pretty ingenious mechanical disengage system.
 
George Thomas has designs for a retracting toolholder and cross-slide in Model Engineer's Workshop Manual. A fine book, btw.

There's also the dog-clutch. Can't remember which book detailed it (maybe an Ian Bradley one?) but there are a few designs online.
 
mikey said:
Small wonder you like that lathe so much!
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Noticed the compound? It is set at the same angle as the 223 reamer body. I set it up sweeping one of the flutes with the reamer and it has been in that position for the last 3 years. After dialing the bore I drill, follow with a boring using the compound, then finish ream.

Threading? Plunge straight in with the cross slide Spindle at over 300 and lay down inserts on 416R SS, no problem.
 
Lonnie and Bamban - Both your stops are fantastic! Great adaptations to fit your lathes. I did one, based on a microswitch. It's described at https://www.hobby-machinist.com/threads/carriage-stop-for-g4003g.81936/ ... post #30. The microswitch activates very consistently - something like .001" of carriage travel. With a braking resistor installed on the VFD, the chuck stopped within about 5 degrees (10 trials) when turning at 100 RPM.

jmarkwolf - The action of the VFD is to remove power from the motor and then "short" the windings together (through the electronics) to give dynamic braking when you hit the stop switch. (my microswitch stop is wired in series with the "run while closed" stop control.) Stopping time is set by a parameter entered into the VFD. Without a braking resistor, the ability of the electronics to "dump power" limits this to about 2 seconds. With a resistor, you can go lower. I have mine set for a ½ second stopping time.

The mechanical system you linked to is also pretty nice. I'd seen it before, but just didn't think I could adapt it to my own lathe. I found it easier to implement the stop electronically.
 
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