Taiwan lathe spindle runout

TRA said:
I think the biggest mystery is.........Is perfect really necessary?
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Even though we strive to remove as many variables as possible, It is my opinion that "perfect" is not necessary, and in most cases not obtainable.

But then the question is asked......"how far from perfect is acceptable"?

Which brings us back to striving to remove as many variables as possible.
 
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TRA said:
FWIW, If you try to stop the spindle without withdrawing the tool it will break the tool. With carbide that has multiple cutting edges it trashes the whole insert. When it absolutely must be done this way, the thread is cut into a hole at the end of the thread. You may be able to pre machine a relief between the thread and the shoulder and stop it there. The tool will have to be clear of the thread when you stop the spindle. That's one of the cons to CNC machinery. When the power causes the relays to drop out, or total loss of power, things get broke, parts get trashed.
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tra, have you used an old (1956 for example) that has ELSR. The Monarch 10EE for example? You might want to rethink your post. The trial testing of Nez's idea has been in a previous video. It appears to work without problems.
I'm sure you are pretty knowledgeable about machine theory and CNC, but keep an open mind.
 
Butch Lambert said:
tra, have you used an old (1956 for example) that has ELSR. The Monarch 10EE for example? You might want to rethink your post. The trial testing of Nez's idea has been in a previous video. It appears to work without problems.
I'm sure you are pretty knowledgeable about machine theory and CNC, but keep an open mind.
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If you are going to continue to throw out that 10EE w/ELSR we might just as well talk MAZAK's. The post I read mentioned ACER and JET....not Monarch. The electronics and the motor on a Monarch is not in the same universe as ACER/JET.

We use drives like what he's speaking of when "in position error" is irrelevant, but if you want to precisely control motors you drag out the servo hardware. By then you would have more money invested than you could buy a used small CNC for.

The fact remains, if you stop the spindle with the threading tool still engaged you will have less than optimum results. Been there done that.
 
TRA said:
If you are going to continue to throw out that 10EE w/ELSR we might just as well talk MAZAK's. The post I read mentioned ACER and JET....not Monarch. The electronics and the motor on a Monarch is not in the same universe as ACER/JET.

We use drives like what he's speaking of when "in position error" is irrelevant, but if you want to precisely control motors you drag out the servo hardware. By then you would have more money invested than you could buy a used small CNC for.

The fact remains, if you stop the spindle with the threading tool still engaged you will have less than optimum results. Been there done that.
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http://benchrest.com/images/icons/icon10.png

You're eat up with your knowledge, so let's see what Nez turns up with his project. No, I've not broken an insert in my old fashioned 10EE.
 
Ignorance is bliss, failure is an option

A year ago as I ventured into hot rodding my other 1024 lathe, came up with and idea to use the DRO to automatically shut down the spindle through some decision process. Basically move the cutting bit to the desired stopping point, zero the DRO, move carriage to the starting point, start the process, once the cutter reaches zero on the DRO, the interface box will output a signal to stop the VFD.

Tested concept on the cross slide for repeatability

https://www.youtube.com/watch?v=mVCkBcgejNk



Then on the carriage by setting the zero where the boring bar stops to see how well it handles a longer run

https://www.youtube.com/watch?v=JDc-r-YcNG4



Then made a couple of banzai runs with the threading bit

https://www.youtube.com/watch?v=f67CXnVtW6U


There are a few things not taken into consideration initially, like keeping the threading bit engaged when the spindle stops, but an auto retract might not be that difficult to add on. I've ssen some manual retractable tool holder. I know threading to a thread relief cut the system works. I am still too chicken to thread to a shoulder.

Maybe on the Jet 1024 a proximity sensor would suffice to generate the signal fast enough to accomplish what I wanted to do, if not I can alwayos go back to the DRO driven system and tweak/enhance it from there

Ignorance is bliss, failure is an option.
 
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I have read this thread, and I still can't figure out why you need to stop a lathe this suddenly. The only time I could see a need for this would be if you were threading a metric thread to a shoulder on a lathe with an American lead screw, where you can't disengage the half nut and must stop and reverse the machine.

Or maybe I am missing something in the conversation.
 
jackie schmidt said:
I have read this thread, and I still can't figure out why you need to stop a lathe this suddenly. The only time I could see a need for this would be if you were threading a metric thread to a shoulder on a lathe with an American lead screw, where you can't disengage the half nut and must stop and reverse the machine.

Or maybe I am missing something in the conversation.
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Jackie,

Thank you. No need for the most part, it was just a concept on how to automatically stop spindle at a pre-determined spot.

Nez
 
jackie schmidt said:
I have read this thread, and I still can't figure out why you need to stop a lathe this suddenly. The only time I could see a need for this would be if you were threading a metric thread to a shoulder on a lathe with an American lead screw, where you can't disengage the half nut and must stop and reverse the machine.

Or maybe I am missing something in the conversation.
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You are missing something. 99% of the people that do gun work have not near the experience you do threading to a shoulder. I don't use a thread relief even though it hurts nothing to have one on a barrel. I think it looks much better without a thread relief.
 
Another FWIW, There's a gadget called a TRAV-A-DIAL that mounts on the rear of the carriage and is a measuring device that measures travel in the Z axis. They come in handy for threading as you can zero it out where you want the thread to stop. You then watch the dial and don't watch the thread. Takes a lot of the shoulder panic out of it. I know a guy that can thread at almost CNC speeds by stomping on the brakes and withdrawing the cross slide at the same time. Needless to say he has reflexes like a cat.....mongoose even.

I would not own a manual lathe without a Trav-A-Dial. Again...just... FWIW

I wouldn't give a nickel for a DRO. The best place for a dro is buried on some shelf in a corner. They are so-so on a mill, but worthless IMHO on a lathe.
 
NezRongero said:
Jackie,

Thank you. No need for the most part, it was just a concept on how to automatically stop spindle at a pre-determined spot.

Nez
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Actually it's a good idea for those hobbyists that may only thread something a couple of times a year. Trouble is it's more complicated than it seams.

I would think a carriage stop would be the hot ticket.
 
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TRA said:
Another FWIW, There's a gadget called a TRAV-A-DIAL that mounts on the rear of the carriage and is a measuring device that measures travel in the Z axis. They come in handy for threading as you can zero it out where you want the thread to stop. You then watch the dial and don't watch the thread. Takes a lot of the shoulder panic out of it. I know a guy that can thread at almost CNC speeds by stomping on the brakes and withdrawing the cross slide at the same time. Needless to say he has reflexes like a cat.....mongoose even.

I would not own a manual lathe without a Trav-A-Dial. Again...just... FWIW

I wouldn't give a nickel for a DRO. The best place for a dro is buried on some shelf in a corner. They are so-so on a mill, but worthless IMHO on a lathe.
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On my 10 inch Pratt & Whitney, I thread at 275 rpm, to a shoulder, with a verticle mount insert holder.I set the carriage stop to where the tool comes within about .032 of the shoulder. I just look at that and pull the cross slide Back while simutaniously kicking the half nut out. You get into a rhythm.
 
Or in the absence of a travail or carriage stop, simply move the tool to within s few thousands of the OD to be threaded, and within about 1/16 of the shoulder. Then using a Sharpie, make a mark on the way next to the left carriage wing. Back the tool off so it will not hit the shoulder and with the spindle running, practice backing the tool out with your left hand while simuntsnously disengaging the half nut while watching the mark instead of watching the tool tip.

Practice this till you get the feel. What sometimes happens when you are watching the tool tip is if a chip rolls up or the tool emits a puff of oil smoke just as the tool tip approaches the shoulder you loose your concentration and confidence.

Threading at 275 rpm? Most amatures should not even try that.

If you are getting tool chatter while threading you may have 1) too much workpiece overhang, or 2) the tool tip is above or below center, or, 3) the wrong tool tip geometry for that material. Ideally a 7 degree positive tool should be used for threading steels used for gun barrels.

.
 
JerrySharrett said:
Or in the absence of a travail or carriage stop, simply move the tool to within s few thousands of the OD to be threaded, and within about 1/16 of the shoulder. Then using a Sharpie, make a mark on the way next to the left carriage wing. Back the tool off so it will not hit the shoulder and with the spindle running, practice backing the tool out with your left hand while simuntsnously disengaging the half nut while watching the mark instead of watching the tool tip.

Practice this till you get the feel. What sometimes happens when you are watching the tool tip is if a chip rolls up or the tool emits a puff of oil smoke just as the tool tip approaches the shoulder you loose your concentration and confidence.

Threading at 275 rpm? Most amatures should not even try that.

If you are getting tool chatter while threading you may have 1) too much workpiece overhang, or 2) the tool tip is above or below center, or, 3) the wrong tool tip geometry for that material. Ideally a 7 degree positive tool should be used for threading steels used for gun barrels.

.
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I used the sharpie method for yaears on the manual machine. It's much easier than trying to follow a dial.

Edit: I think it would have to be an emergency before I stopped the spindle while a tool was still in a cut. I've got a foot brake on my manual lathe and think the only time I have used it was to test it after I got the machine powered up for the first time.
 
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I gutted a micrometer stop for the body, and simply use a 2" travel dial indicator with a mag mount in stead of a trav a dial. Slides right on the ways where I need it.
 
tra, I actually have 2 Trav A Dials. I think that they are best for threading. The Sharpie is great and I used it before my Trav A Dials.
 
I use the mag base travel dial indicators. and a 2"on my talestock.
I use whatever speed feels good from 100 rpm to 260 rpm I dont usually go that fast up to a shoulder except fine treads like a 32 maybe a 24.
 
Gents,

Ditto on the Sharpie mark on the ways. I've threaded into a shoulder at 250 rpm's using this method and never had a problem. Simple usually works best...

Another thing I do that seems to help when threading at high rpm is to set my tool a ways away from my work. This allows me ample time after engaging the thread lever to get positioned and comfortable, and not fumbling around while the shoulder is rapidly approaching.

But now I have a Brown threading tool with HSS inserts, and thread at HSS speeds. Much easier on the ol' blood pressure.

My dad thinks I'm nuts for threading into a shoulder and walks out of the shop when I do it, presumably, not to get hit by shrapnel from the crash. He is always telling me to turn the tool upside-down and thread out.

Justin
 
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