Using clutch vs half nut on 10H
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    Question Using clutch vs half nut on 10H

    My last lathe was an Atlas, so I used the half-nut to engage longitudinal feed. Seldom use power feed so I have been using half nut lever instead of clutch on my recently acquired 10H, as it is more convenient and feels more precise when coming to the stop. Bothers me the clutch knob rotates when engaged. I saw a video from MRPETE222 and he emphasized safety advantage of using clutch in case of a crash. Are there other reasons to use clutch rather than half nut ?

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    Quote Originally Posted by Vandegraaff View Post
    My last lathe was an Atlas, so I used the half-nut to engage longitudinal feed. Seldom use power feed so I have been using half nut lever instead of clutch on my recently acquired 10H, as it is more convenient and feels more precise when coming to the stop. Bothers me the clutch knob rotates when engaged. I saw a video from MRPETE222 and he emphasized safety advantage of using clutch in case of a crash. Are there other reasons to use clutch rather than half nut ?
    Wow, I’ll be interested to see the reply’s to your question.

    So I’ll try to give you a simple run down.

    You should always find the proper feeds and speed for whatever your cutting.

    You use the power feed to do the hard work and the clutch as a safety to prevent self destruction of your lathe in a bind.

    You use the half nuts and feed screw to cut threads ONLY.

    On a southbend The difference between a toolroom lathe and a regular floor model is the precision of the lead screw.

    If you use the half nuts to do basic turning then your burning up your valuable precision lead screw.

    Your lathe may no longer cut proper threads as you wear your half nuts and screw from improper use.

    I can tell you if your lathe was a tool room version, IT AINT anymore.

    Stop using the half nuts immediately and do some learning on how to run a lathe

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    If the clutch knob spinning bugs you then upgrade it to the lever style clutch.

    You shouldn’t need to adjust the clutch often, I set it and forget it, I don’t use a stop, I have 2 micro meter stops and once in awhile the stops will slip so I’ve gotten used to just stopping short and creeping up on my stop manually

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    +1 on what the blob said. You will unnecessarily put wear on both the lead screw and the half nuts using them for your feed. TRAIN yourself and GET USED to the proper operation of your particular lathe. I used a 9C for years (which DID operate like your Atlas) and using the carriage properly took some getting used to, but once I got the hang of it, I wouldn't go back.

    Also, do NOT depend on the clutch to prevent crashes - that's not its purpose. The clutch can hold so tight that it can shear gear teeth on a crash. You prevent a crash by keeping your head out of your you-know-where.

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    THanks all. I Understand wear issue,theoretically but I wonder if it will be that significant. The worm drive on the clutch has just 4 segments interfacing with the lead screw so longitudinal effort will be more per leadscrew thread than the half-nut as it grips 320 (?) degrees around the leadscrew with maybe 16 threads spreading the force over more threads of the leadscrew. I can see how the 320 degrees will wear leadscrew faster as it touches more threads but force is better distributed. I will operate clutch as the "experts" say but not all lathes have such clutches and it sure isn't conveniently located so I can see why they came up with lever clutch improvement.
    BTW, thanks for info on the difference between toolroom and standard lathes.

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    power feed thru the apron gearing is one of the more useful features on a lathe

    once you get usd to it youll never use the halfnuts again for it

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    Quote Originally Posted by Vandegraaff View Post
    The worm drive on the clutch has just 4 segments interfacing with the lead screw so longitudinal effort will be more per leadscrew thread than the half-nut as it grips 320 (?) degrees around the leadscrew with maybe 16 threads spreading the force over more threads of the leadscrew.
    The worm gear interfaces with the lead screw via a key (and a slot in the LS), so there is no wear on the LS threads when using the clutch. The LS threads are used only with the half-nuts.

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    In addition to what everyone said, using the clutch gives me power cross feeds as well as longitudinal. And believe me, the clutch feeds (instead of the lead screw) can be a lot finer than the screw feeds.

    I routinely turn up to a shoulder with the clutch. You need to be awake to do this, not mind wandering. I usually set a bed stop and undo the clutch just before the carriage gets to the stop. Finishing by hand using the carriage wheel works fine. I can undo the clutch within .030 before the shoulder just by eye and practice.

    Same goes for threading, using the bed stop and a runout groove.

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    Quote Originally Posted by Vandegraaff View Post
    THanks all. I Understand wear issue,theoretically but I wonder if it will be that significant. The worm drive on the clutch has just 4 segments interfacing with the lead screw so longitudinal effort will be more per leadscrew thread than the half-nut as it grips 320 (?) degrees around the leadscrew with maybe 16 threads spreading the force over more threads of the leadscrew. I can see how the 320 degrees will wear leadscrew faster as it touches more threads but force is better distributed. I will operate clutch as the "experts" say but not all lathes have such clutches and it sure isn't conveniently located so I can see why they came up with lever clutch improvement.
    BTW, thanks for info on the difference between toolroom and standard lathes.
    the lead screw on a 10h I think is like the 9A... it does not engage the threads when feeding. It uses the groove in the lead screw to drive the feed. it's always turning ..

    use the feed for feeding, and half nuts for threading.
    The feed also operates the cross slide feed too.

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    Quote Originally Posted by Vandegraaff View Post
    THanks all. I Understand wear issue,theoretically but I wonder if it will be that significant. The worm drive on the clutch has just 4 segments interfacing with the lead screw so longitudinal effort will be more per leadscrew thread than the half-nut as it grips 320 (?) degrees around the leadscrew with maybe 16 threads spreading the force over more threads of the leadscrew. I can see how the 320 degrees will wear leadscrew faster as it touches more threads but force is better distributed. I will operate clutch as the "experts" say but not all lathes have such clutches and it sure isn't conveniently located so I can see why they came up with lever clutch improvement.
    BTW, thanks for info on the difference between toolroom and standard lathes.
    You are incorrect.

    As others said the lead screw has a key way cut into the side of the screw.

    Other lathes have 2 or more shafts through the apron. 1 screw for threading, and a shaft (sometimes keyed, other times Square or octagonal).

    On other lathes the lead screw is engaged with half nuts only while the “other shaft” is used instead to drive the power feeds using a gear rack NOT a lead screw

    Here’s a pic from a thread in 2008
    e184a056-1b9a-462c-ba25-4ceb59a6fe71.jpg

    As you can see southbend decided to combine the two shafts into one.

    When your power feeding with the clutch your NOT engaging the lead screw threads AT ALL.

    Instead it’s using the spinning key way to drive a transmission that is engaging the gear rack under the ways

    Your understanding of the mechanics is very wrong, you need to research in depth the fundamentals and operation of a southbend if you want to answer your own questions otherwise listen and heed the advice of others on here who have a more in-depth understanding of the lathe in question

    Ps: you can drop the quotations around “experts”.

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    as a point of reference and not intending to pile on, but the powerfeed key in my '29 apron was worn 1/2 way through but the half nuts still have probably 80% of their life left when I got it. Made a new key out of a bit of key stock I had lying around. New half nuts (if available!) are in the range of $125-150.

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    Quote Originally Posted by mattthemuppet View Post
    as a point of reference and not intending to pile on, but the powerfeed key in my '29 apron was worn 1/2 way through but the half nuts still have probably 80% of their life left when I got it. Made a new key out of a bit of key stock I had lying around. New half nuts (if available!) are in the range of $125-150.

    I second that sentiment. I wouldn't want you to have my experience.

    My 13 in SB was abused by the PO who used the half nuts for longitudinal feed and I HAD to replace them. The half nuts were razor thin.The new (old stock) ones were a bugger to find and were costly - almost as much as the lathe.
    Plus it is a real PITA to change those half nuts.

    Longitudinal feed makes no wear on the half nuts or on the lead screw. As others said, please use the half nuts for thread cutting only.

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    Another comment for no particular reason: I always sort of liked the star-wheel clutch. My first 10L had that, my new one is lever clutch.

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    Quote Originally Posted by jim rozen View Post
    Another comment for no particular reason: I always sort of liked the star-wheel clutch. My first 10L had that, my new one is lever clutch.
    I also prefer the star wheel clutch. I had the opportunity to replace it with a lever clutch, but I turned it down.

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    I like the star wheel because you can actually "feel" it just like you would a car or motorcycle clutch -- It's a clutch, not an on-off switch.

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    The half nuts and the power feed are two different systems inside the apron. That's why there's a lockout to prevent closing the half nuts when the power feeds are selected.

    The feeds provided by the clutch are much finer than the thread pitches from the half nuts. If you have much metal to remove you will want to take advantage of this with deep cut at a very fine feed.

    It would be well worth your time you find a copy of South Bend's How To Run a Lathe.

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    Quote Originally Posted by SLK001 View Post
    The worm gear interfaces with the lead screw via a key (and a slot in the LS), so there is no wear on the LS threads when using the clutch. The LS threads are used only with the half-nuts.
    This is one of the reasons why disassembled my lathe completely for restoration, sovo would know what's inside and know how the lathe works.


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