Lathe carriage stop

extropic said:
@Charles scozzari

Please elaborate on the intention of the smaller (1/4"?) diameter portion of the stop rod and particularly the groove (1/8" ID?)

I like the idea. I'm away now, but when I get home I intend to see if your concept is easy to implement on my lathe's configuration.
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I believe this can be made to work on any lathe large or small including lathe heads mounted on top of the bed by having a stop mounted between the ways. Thanks for your interest and question.
 
I did try to dream up a two-stage limit switch, interlocked with the power feed. A stop within a spring loaded tube, and a switch sensing the feed lever, or mechanism. The idea is that if you are manually feeding, you can go all the way to the solid stop.

If, by some chance, you forget, and have the power feed on, you have effectively "armed" the first level limit switch to bring the lathe to a halt when it finds the spring-loaded limit switch on the stop. Lathe coming to a halt is assisted by motor dynamic braking into a resistor load. A swift stop, but not violent, yet rapid enough that the spring loading is not completely taken up.

It was a pipe dream scheme. So far, I have not messed up, but I keep refining it in my mind. :)
 
graham-xrf said:
I did try to dream up a two-stage limit switch, interlocked with the power feed. A stop within a spring loaded tube, and a switch sensing the feed lever, or mechanism. The idea is that if you are manually feeding, you can go all the way to the solid stop.

If, by some chance, you forget, and have the power feed on, you have effectively "armed" the first level limit switch to bring the lathe to a halt when it finds the spring-loaded limit switch on the stop. Lathe coming to a halt is assisted by motor dynamic braking into a resistor load. A swift stop, but not violent, yet rapid enough that the spring loading is not completely taken up.

It was a pipe dream scheme. So far, I have not messed up, but I keep refining it in my mind. :)
Click to expand...
Hello, WOW I was going with using a normally closed micro mounted at the 5/8" threaded rod and extending onto the what I am referring to as the bulb If I am understanding your approach the spring will void the solid stop feature. I thank you for your interest and idea. It is food for thought.
 
@Charles scozzari

I'll try again.

Please elaborate on the intention of the smaller (1/4"?) diameter portion of the stop rod and particularly the groove (1/8" ID?)
 
Charles scozzari said:
Hi, I am working on a devise that along with the bulb in question would snap the bulb and trigger the emergency stop circuit through a micro switch before crashing the carriage into the chuck. Without the bulb as part of the stop circuit setting a micro switch to trigger the stop would remove the solid stop design. At present I am using it as it is. I may abandon the idea and cut the bulb off since it works well as is, and I still would have the shear pin as a safety. Thanks and hope this helps explain the intended use of the bulb. Charlie
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Bulb? I don't see anything in the picture that I recognize as a bulb. Since you didn't address the reply to me, I didn't recognize it as trying to answer my question.

I interpret your intent to be that the features I asked about are for a potential design option.
 
Charles scozzari said:
Hello, WOW I was going with using a normally closed micro mounted at the 5/8" threaded rod and extending onto the what I am referring to as the bulb If I am understanding your approach the spring will void the solid stop feature. I thank you for your interest and idea. It is food for thought.
Click to expand...
Hi Charles
I thought one needed some sort of reliable thing to signal when the power feed lever is in ON position, which provides the first half of the logic.

The next thing that needs to be sensed is when the carriage really must not be going any closer (under power). Something that will take it out of trouble before it hits the solid stop. The closed limit switch riding on the carriage stop provides that, and it will move, along with the stop, to wherever you set it.

Mechanically, it could be a coaxial tube, or a separate rod or whatever, but the key thing is that it operates a bit before the carriage hits the stop, while not actually stopping anything if the carriage is being moved safely by hand.

Let us ignore complicated stuff like using an actuator to yank the feed lever out of engagement. The simpler, cheaper, way, that gets your attention, is to just wire the two switches in series with the lathe E-Stop. Spring load a rod if you like, but you don't have to. You can avoid crushing the limit switch by using one of the many switch shapes with lever bumps that can operate the switch as it "passes by".

Dynamic braking is a refinement if the lathe keeps coasting on to a long halt from inertias. If the limit has a sufficient gap to the hard stop, it will work anyway.

Lathe Stop Limit.jpeg

OK - it's a quick 'n dirty scribble that may not yet be mutt's nuts, but the idea is that if the power feed is in a "safe" position, i.e. not engaged, the anti-crash limit switch is bypassed via the NO (normally open) contact on the power feed sensing switch. If the power feed is engaged, it will have to obey the anti-crash limit switch, which can be set with some gap before the hard stop. If you ride into it with the power feed lever ON, the lathe will stop before it rides into the hard stop.

I am sure that folk here can come up with refinements, and all manner of various tidy mechanical arrangements that will do this, but it's a start. :)
 
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graham-xrf said:
Hi Charles
I thought one needed some sort of reliable thing to signal when the power feed lever is in ON position, which provides the first half of the logic.

The next thing that needs to be sensed is when the carriage really must not be going any closer (under power). Something that will take it out of trouble before it hits the solid stop. The closed limit switch riding on the carriage stop provides that, and it will move, along with the stop, to wherever you set it.

Mechanically, it could be a coaxial tube, or qa separate rod o whatever, but the key thing is that it operates a bit before the carriage hits the stop, while not actually stopping anything if the carriage is being moved safely by hand.

Let us ignore complicated stuff like using an actuator to yank the feed lever out of engagement. The simpler, cheaper, way, that gets your attention, is to just wire the two switches in series with the lathe E-Stop. Spring load a rod if you like, but youu don't have to. You can avoid avoid crushing the limit switch by using one of the many switch shapes with lever bumps that can operate the switch as it "passes by".

Dynamic braking is a refinement if the lathe keeps coasting to a halt from inertias. If the limit has a sufficient gap to the hard stop, it will work anyway.

View attachment 401780

OK - it's a quick 'n dirty scribble that may not yet be mutt's nuts, but the idea is that if the power feed is in a "safe" position, i.e. not engaged, the anti-crash limit switch is bypassed via the NO (normally open) contact on the power feed sensing switch. If the power feed is engaged, it will have to obey the anti-crash limit switch, which can be set with some gap before the hard stop. If you ride into it with the power feed lever ON, the lathe will stop before it rides into the hard stop.

I am sure that folk here can come up with refinements, and all manner of various tidy mechanical arrangements that will do this, but it's a start. :)
Click to expand...
you can also use reed switches. They come in both normally open and normally closed. but they require a magnet (oh that doesn't work with metal like it does with wood)...
 
woodchucker said:
you can also use reed switches. They come in both normally open and normally closed. but they require a magnet (oh that doesn't work with metal like it does with wood)...
Click to expand...
A reed switch would work, even if there is some aluminium between it and the magnet, and they are way more reliable than micro-switches. A little magnet on the end of a rod could work.
BUT
One likes something enclosed, and not gathering a huge pile of magnetic chips and crud, The thinking needs to be for simple, elegant, robust, cleanable, reliable.
 
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