Threading to a shoulder

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earlgo
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Re: Threading to a shoulder

Post by earlgo »

Never heard of half-nuts not releasing, but that just means that I don't get around much.
What you need is a worn out ATLAS because sometimes one has to hold the half-nut lever down to keep it engaged. When I got it I replaced the half nuts made from brass with ones made from cast iron.
When we cleaned out my dad's basement we found the original lead screw, and it looked more like it had light bulb threads rather than ACME. I'd bet that the half-nuts never locked up on that one.
--earlgo
Before you do anything, you must do something else first. - Washington's principle.
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mcostello
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Re: Threading to a shoulder

Post by mcostello »

When half nuts don't release it is an adrenaline rush that has to be experienced to be believed. Calling up super human strength is quickly next on the list. I always keep a very firm hold on the lever, Don't thread many 50" long shafts.
johnfreese
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Re: Threading to a shoulder

Post by johnfreese »

Those of us who have lathes with threaded spindles would be foolish to try this.
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Harold_V
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Re: Threading to a shoulder

Post by Harold_V »

johnfreese wrote:Those of us who have lathes with threaded spindles would be foolish to try this.
Depends. If the chuck is set well and no quick starts are employed, you should be able to take decent cuts without unwinding the chuck, even without having any type of locking device in use. However, your point is well taken and is one of the reasons why threaded spindles died off relatively quickly for industrial equipment, where reverse capability for lathes isn't a luxury, but a necessity.

I would go far out of my way to avoid a threaded spindle, given reasonable options. They are too limiting.

Harold
Wise people talk because they have something to say. Fools talk because they have to say something.
Magicniner
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Re: Threading to a shoulder

Post by Magicniner »

johnfreese wrote:Those of us who have lathes with threaded spindles would be foolish to try this.
Not really, we (I have a Myford Super 7) just need to address the problem.
If your chuck backplate has a boss you just need a groove in the register and aligning locking screws in the boss, a very easy modification on many lathes with chucks which screw onto the register.

- Nick
earlgo
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Re: Threading to a shoulder

Post by earlgo »

johnfreese wrote:Those of us who have lathes with threaded spindles would be foolish to try this.
This ATLAS lathe has a threaded spindle nose. I don't do anything special to tighten the face plate. I stuck the handle of an 8" crecent wrench in the slot and pushed.
If you are a 'threader' who likes to take .015 at a pass, then unscrewing might be a problem, but I never take more than .005 at a pass and so far, unthreading has not been an issue. Maybe all the proper precautions have made me lucky.
--earlgo
Before you do anything, you must do something else first. - Washington's principle.
pete
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Re: Threading to a shoulder

Post by pete »

Joe Pieczynski on Youtube did a great video some months ago about threading away from the chuck and why it's his favorite method. A book I've mentioned more than a few times here before would be George Thomas's The Model Engineers Workshop manual has the working drawings for building both a lever operated threading tool holder and the same for a lever operated top slide for the Myford Super 7 lathe. Not too tough to redesign larger or for different top slides if you wanted to. The lever tool holder only works on external threads, but the top slide works for internal and external. Threading away from the chuck is obviously the safest method and you'd have to be trying to have a crash to do so. But the lever operated tool holder or top slide is still helpful while threading in either direction since there's no need to back up the cross slide.I first learned single point threading on a little Emco Compact 5 lathe that doesn't have half nuts, and it's minimum rpm is 250. 3/4" x 16 tpi gets pretty exciting. A hand crank on the left end of the spindle was a real help.
whateg0
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Re: Threading to a shoulder

Post by whateg0 »

I've always wanted to be able to do that. My old lathe didn't have a backgear. I removed a couple of gear when I made the new spindle, but the way it was configured when I bought it had no way of disengaging those gears, so it was awfully slow with the double reduction. When I removed those, I ended up with a ~700 rpm spindle speed at all times, and that's what I have been threading at all the time since. I've gotten to where I can disengage the half nuts and end up in the middle of my 0.100-0.125" runout area pretty consistently, but there's always a strong pucker factor.

One reason I never tried running backward, though, was that I had always read that with my threaded spindle, I ran the risk of unthreading it. The last time I removed the chuck, I think I convinced myself that there was no way that was going to happen as I thought I would have to beat the thing to death to get it to unthread.

Anyway, when I've needed to thread to a shoulder and couldn't use a runout area, I had started pulling out toward the end of the thread and then disengaging the halfnuts. Do that until I'm near my final depth and go back and turn the spindle by hand to finish the rest of the threaded area, and on the final pass run the whole length of the threads or finish with a die. Worked incredibly well, and I was amazed at how easy it was to turn the spindle even with what I felt were awfully deep cuts.

Now that the 10ee is almost ready to use, I am anxious to try out the elsr, even without being able to stop on a dime yet. When I'm able to add a braking resistor, that should become a reality again and then it should be a pleasure to thread. And I want to try threading on the backside with the spindle running CW now, too.
spro
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Re: Threading to a shoulder

Post by spro »

I do imagine how cool this will be with the 10EE. People don't appreciate these dramatic steps unless they experienced the first ones.
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Harold_V
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Re: Threading to a shoulder

Post by Harold_V »

While it isn't a real useful feature, and it may or may not be an accessory on all EE's, the one I trained on had a stop that shut off the spindle. With that stop you could thread a full thread (in soft material, and at a constant speed) right up the termination point. That would break the tip from carbide, or from HSS in tough materials, but I did it once, threading aluminum, just to see if it would work. And it did! Looks real strange to see a full thread which abruptly comes to an end, full depth.

H
Wise people talk because they have something to say. Fools talk because they have to say something.
whateg0
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Re: Threading to a shoulder

Post by whateg0 »

Breaking the insert is a concern, for sure. What I have seen of it, people usually retract the tool at the last moment. At worst, this should produce an uneven load on the tool at the end as one pass is likely to stop short of others. But regardless of that, it does keep one from crashing into the shoulder. My machine doesn't have the Variable Speed Reverse (VSR) and I haven't completely figured out how to implement it. In some ways, as well thought out as the machine is, the ELSR seems like an afterthought. I don't think that it makes it unusable, but, for example, flipping everything to LH threads makes the spindle spin in reverse of what one would expect. IOW, push the lever down normally and the spindle turns fwd, but when threading LH threads, it's spinning the other way. I understand it, but I don't understand the why. People who love it seem to love it and those that don't, don't. I don't know that I'll use the "reverse" feature even if I can add VSR just because it seems faster to retract the tool and spin the handwheel than to wait for the carriage to travel back on its own. For metric threads on an inch machine, it does seem very useful.

Did any other machines have a feature like this that would stop the spindle when threading? I've seen some homebrew solutions that were similar, but am not aware of any other factory options like this.
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Harold_V
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Re: Threading to a shoulder

Post by Harold_V »

I'm not aware of the features of many of the industrial machines, as my limited knowledge has come from operating the machines with which I am somewhat familiar. I have never made a study of machine tools in general, unlike some of the folks who offer comments. Frankly, I'm amazed at their broad, general knowledge.

That said, Patio (on this board) owns a Cazeneuve lathe that has some exceptional features, several that relate to threading. As I'm not nearly as familiar with his machine as he is, I'll not comment, but if he reads this thread, he may.

H
Wise people talk because they have something to say. Fools talk because they have to say something.
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