Stopping the carrage on my lathe at a preset spot. Can it be done ?

When I was in the early years as a power system operator I learned to synchronize a generator to the power system. The synchroscope needle would come up the the dummy at varying speeds, depending on the skill of the operator and the accuracy of the governor. You have to account for the speed of the synchronizing breaker as well as the speed that the scope is moving - a bit of an art. Everybody hit it hard on occasion! I have always thought that disengaging the carriage drive was much like that.
I have always thought that an automatic carriage stop was the great breakthrough in lathe design that has never happened. If it had become a popular function it would sure have saved us all a lot of stress!

MIchael
 
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I feel the same way but think economics play a big part. Manufacturers in-general stay up at night thinking of ways to reduce cost. Also, the general issue represents a diving line between a manual and automatic machine. Right now, dedicated "screw machines" are likely totally supplanted by CNC. BTW: The older "screw machines" were semi-adjustable and had those kinds of features as well as automatic or semi-automatic turrets to perform generalized operations to make all kinds of screws, nozzle tips, etc...

Again, it's worth mentioning that any kind of automatic device needs to be attended by the operator. When things go bad, a lot of damage happens in a split second -and I've been very fortunate up to this point...

I have in the past and will in the future, make automatic stops for the carriage -it's all but trivial. If there's anything I'd really like to see in a lathe, it would be metric threading with the simplicity of SAE threading. -Metric threading... Nothing easy or fun about it. About half the propeller shafts I work on have metric threads. When I can get away with it, I cut right hand threads from left to right (i.e) as "reversed left hand". Complications there too because the tailstock and/or center are usually in the way.

Ray


valleyboy101 said:
I have always thought that an automatic carriage stop was the great breakthrough in lathe design that has never happened. If it had become a popular function it would sure have saved us all a lot of stress!
MIchael
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Wow I thought most lathes all had some mechanical feed disconnect means. Definitely see why you would be frustrated not having

papermaker said:
my brothers Logan would disengage the half nut when it contacts the carriage stop. Isn't that what happens on a Bridgeport quill down feed when it contacts the stop or something like that.
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Exactly how the feed on my colchester works. Kind of ingenious how they do it- The feed shaft worm gear floats axially in the apron centered by springs. When carraige hits a hard stop the worm shifts over and disengages the feed. The spring force is adjustable via setscrews on the ends (but only when everythig is disassembled). When i had everything apart for cleaning I had to guess how tight to make the spring preload upon reassembly. I erred on the side of too light as sometimes the feed will kick out when i dont want it to. Better than crashing tho!!
 
I tottaly can see a solonoid for the half nut, but clutch feed is a different story. Thats why I came up
with my 5 min smoke alarm wonder. Apron hits spring- speaker goes off, release clutch or half nut.
I have had dial ind. on there, no good for me, comes down to old eyes. This has been posted long time
ago, as of now same 9vt batt. which is on 24/7. Its a good wake up call. sam
 
The Hardinge HLV-H has an extremely accurate feed stop. I believe it has a dog clutch on the feed screw that is activated by a rod and stop arrangement that the carriage contacts. When the carriage bumps the stop, the rod moves sideways and disengages the dog clutch. Like George pointed out, it'll stop the carriage within a couple thousandths of position when feeding or threading. It looks like there is a lot of room across the front off your lathe bed, perhaps you could adapt a similar system.

Another alternative would be to drive your feed screw with an electric motor. then you could use electric limit switches to stop the feed. It probably wouldn't be as accurate as a mechanical system, but it might be easier to implement. An added perk of electric feed is that the feed rate could be made infinitely variable by using a DC motor with a PWM controller, which is another feature that the Hardinge has.

Tom
 
Have thought about that, but will probably add power feed to the mill X feed first. I have tried using a dial gauge as a "limit indicator" but the old eyes arnt what they used to be, and found it actually easier to watch the work and manually disengage the 1/2 nut. While boring holes in 1" for the mill bearing carrier ends I found it very stressful to concentrate that hard for that long (due to the hole size, the work was about 1/8" in front of the 4 jaw chuck, so I had to let the boring bar go all the way through, but stop feed before the bar found the chuck face. Not really a problem, but a way of kicking out the feed would have made it a little less stressful. Even if I had this feature I would still watch the job, but it would ease my mind a bit.

While I could probably use the existing 1/2 nut, it may be easier to add another and have that kick out when it hits a stop. Will take a closer look today.
 
I've seen a rudimentary, crude setup on a threading setup that was almost laughable. But it worked. Of course, if you are threading into a relief groove, it doesn't have to hit the thousandth. So this isn't the answer to the OP. This setup was comprised of a locking block clamped to the ways on the right end of the lathe. attached to it was a 1/8" wire rope (cable), and the other end was looped around the half-nut lever. A little experimentation led to a setting that pulled the half nuts just as the tool reached the stopping point. I guess no reason the feed lever couldn't be rigged in a similar fashion, but for the older style machines with knobs instead of levers, not too sure it would be workable. And obviously, if you needed the carriage to travel further, the lever loop would need to be removable easily.

Just food for thought.
 
stern said:
Kind of a weird question, but Im looking for a way to "disengage" the carriage from the feed screw on my lathe. Currently I can just use the lever, but want to put an adjustable stop on it, mostly for safety. Sometimes I need to get really close to the chuck and it gets a bit nerve racking watching and playing "beat the buzzer". So far I have had no issues, but find it really draining and would love a way to make it stop feeding at a selected point. The lathe I have is a PM1027 and think it uses a half nut type idea on the feed ON/OFF handle, but not sure. I figured I would check here and see if anyone had ever done something similar. Would be nice to be able to run up to a collar and have the feed stop at the same spot every time.
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You can drop the feed selector handle to neutral or out of gear. On a bigger lathe you may not be able to reach it,
 
Yea, saw the dog cluch post and read it over a few times. Debated it and then decided since I never use the lathe to thread I didnt need to worry about syncing anything, so a simple "trigger fired" mechanism to pop the 1/2 nut is all I really need. Since I probably wont be doing this until after my mill is done Im going to gather as much info as I can and decide then :) Thanks to everyone that helped
 
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