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  1. #21
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    Quote Originally Posted by LexD View Post
    What is a "Double Lead" thread? By definition a thread can only have one lead.
    I believe a more common name is "2 start". This might help show the difference.

    1.2-start.jpg

    A multi start thread has some advantages. They allow the ability to maintain a shallow thread depth relative to their longer lead distance. Another design advantage of a multi-start thread is that more contact surface is engaged in a single thread rotation. A common example is a cap on a plastic water bottle.

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    Metrology is much more than threads so if any have a specific question about threads it might be better to start a new thread or this one could become longer than helpful.

    This could be a goldmine to some.

    International Thread Standards

    This shows what I regard as the most common types.

    http://f-m-s.dk/1.09.pdf

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    Quote Originally Posted by Gordon B. Clarke View Post
    I believe a more common name is "2 start". This might help show the difference.

    1.2-start.jpg

    A multi start thread has some advantages. They allow the ability to maintain a shallow thread depth relative to their longer lead distance. Another design advantage of a multi-start thread is that more contact surface is engaged in a single thread rotation. A common example is a cap on a plastic water bottle.
    Multi Start thread is the correct terminology, whether it is 2,3,4 or whatever number of starts, the thread itself can have only one lead. Multi lead seems to be a term used mainly in the USA.

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    Quote Originally Posted by LexD View Post
    Multi Start thread is the correct terminology, whether it is 2,3,4 or whatever number of starts, the thread itself can have only one lead. Multi lead seems to be a term used mainly in the USA.
    I'd like to avoid discussions on definitions. You may well be correct but by stating the number of starts with a number on a thread then any "mystery" is cleared up from the start.

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    Quote Originally Posted by Gordon B. Clarke View Post
    I believe a more common name is "2 start". This might help show the difference.

    1.2-start.jpg

    A multi start thread has some advantages. They allow the ability to maintain a shallow thread depth relative to their longer lead distance. Another design advantage of a multi-start thread is that more contact surface is engaged in a single thread rotation. A common example is a cap on a plastic water bottle.
    They also allow less run out and vibration than a single start thread. as well as allowing you to spin faster rpms wise with little vibration. Ie they are smoother.

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    Quote Originally Posted by LexD View Post
    What is a "Double Lead" thread? By definition a thread can only have one lead.
    Is this a real question or are you poking?
    I do not know which but discussions over my wording vs yours are sort of a waste.
    If a real question than okay by me as many have never seen dual, triple or quad start threads. Rare stuff.
    It is even good as a pokey here to me but you should maybe put a smiley on the end to let us know the intent.
    We do not know where you are coming from.

    My original post about optical was the ability to check the entire thread form not just the wire or hard gauge
    Often some may have to cheat the wire or other to make the go and no-go fit due to other things going on in the thread form.
    Then you make a decision to trust one over the other and hope the customer does the same.
    Threads can be a complicated form and inspection of all of it can be way too time consuming.
    I'm not so much for trusting my cutting tools as supplied to produce the correct form. I know a bit about that side of the world and how the sausage is made.
    Bob

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    If any want to start discussions on "correct terminology or definitions" I suggest they start a new thread. Maybe even in another sub forum. It'd often be as pointless and futile as discussing which is better, metric or imperial. Each to his/her own and that refers to both countries and people.

    This thread was started as a guideline so will probably soon be closed.

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    Quote Originally Posted by Gordon B. Clarke View Post
    ......This thread was started as a guideline so will probably soon be closed.
    IMO that would be bad. A thread on threads and the many takes on it. What could be the downside?
    Surely as shit many disagreements will show up but is that not good?
    Open discussion, radical or not. Let it ride.
    You opened this box, do not shut it so fast if all this goes way sideways from what you expected. Be open to all.
    Bob

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    Quote Originally Posted by CarbideBob View Post
    IMO that would be bad. A thread on threads and the many takes on it. What could be the downside?
    Surely as shit many disagreements will show up but is that not good?
    Open discussion, radical or not. Let it ride.
    You opened this box, do not shut it so fast if all this goes way sideways from what you expected. Be open to all.
    Bob
    Go back and read the OP. Closing this thread doesn't mean the end of screw thread questions. What is happening is that this thread is becoming filled with posts some of which are more screw thread relevant than others.

    Metrology is much more than "just" screw threads and as good as all new threads deal with specific issues. If someone asked about a specific thread type it'd get lost in this one.

    Let's say some were interested in Buttress or API threads then they should both each have their own thread. Same with all other metrology related topics such as simple inexpensive everyday measuring equipment or the more expensive. Also questions on equipment (bought or thinking about buying) are OK.

    It'd be nice if this was the "go to" forum for help with metrology issues. I've noticed many metrology questions crop up in other sub fora. I've certainly nothing against that but it probably limits the responses.

    There were things Leigh knew a great deal about and often pitched in. Same with me although not the same things as with leigh.

    If you look at the 4 threads I closed none of them had anything to do with metrology. I'm sure Leigh would have done the same.

    I've cleared some space in my PM but emails are probably better.

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    Dunno Gordon, but to me, JMHO, closing threads that are on topic for the forum because of thread drift is not all that productive. Do what you please but I would think the goal would be interest in the subject and thus the forum. Bumping 10 year old threads, sure, dumb, but a little thread drift never hurt anyone.........much

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    Quote Originally Posted by gustafson View Post
    Dunno Gordon, but to me, JMHO, closing threads that are on topic for the forum because of thread drift is not all that productive. Do what you please but I would think the goal would be interest in the subject and thus the forum. Bumping 10 year old threads, sure, dumb, but a little thread drift never hurt anyone.........much
    Your opinion but you're using this thread to post something that has nothing to do with screw threads. I've deleted a couple of posts in this thread for the same reason.

    If someone has a question or useful information about a specific screw thread or type then, as everything else about metrology, start a thread dealing with that particular thread or subject. If you look at as good as all other threads in Metrology they're all more or less about specific subjects that have to do with metrology.

    Following your advice then this sub forum need only have one single thread called Metrology. As I understand it then a thread title is so people can see right away what the thread is about. In fact Milicron has more than once insisted on thread titles being specific and logical.

    One thing we certainly can agree on is that the more posts a thread gets the more it "drifts".

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    Gordon, Starrett used to have a thread gaging reference quide that you could download. I have it here on my desk and it goes pretty good into different things to check about threads and different ways to do it. The cover says it was distributed by Gage Crib worldwide inc or Grand Rapids Michigan.

    I printed it out and dont have it on my computer any more, this was from about 10 years ago. Perhaps it is still available for people to use?


    Ok I found it, not that hard actually...

    https://www.ring-plug-thread-gages.c...ence-Guide.pdf

    Charles

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    Quote Originally Posted by CBlair View Post
    Gordon, Starrett used to have a thread gaging reference quide that you could download. I have it here on my desk and it goes pretty good into different things to check about threads and different ways to do it. The cover says it was distributed by Gage Crib worldwide inc or Grand Rapids Michigan.

    I printed it out and dont have it on my computer any more, this was from about 10 years ago. Perhaps it is still available for people to use?


    Ok I found it, not that hard actually...

    https://www.ring-plug-thread-gages.c...ence-Guide.pdf

    Charles
    Charles,

    Starrett wanted to buy my thread measurement system years ago but on the condition that they themselves manufactured. I said no.

    I've known the guy that has Gage Crib for years and we exchange emails now and then although far from often. I only have good things to say about Gage Crib.

    I'm sure some can use the Starrett information you enclosed. Personally I've got what most would regard as a library but I might just print it. I wish though, when companies make something like that, they'd give some thought as to how many pages must be printed and put more on each page.

    Years ago I made something similar but not as detailed. Only 4 pages though

    http://f-m-s.dk/1.04.pdf

    Gordon

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    Gordon, I know the pamphlet I linked to is geared toward you buying the tool from Starrett. But it might be helpful to others. I have another one that goes into much more detail but dont have a way to share it. One day I might get a scanner. Have a great holiday, I still love the caliper tension tool I got from you, it really works.

    Charles

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    Quote Originally Posted by Gordon B. Clarke View Post
    I believe a more common name is "2 start". This might help show the difference. Correct

    A multi start thread has some advantages. They allow the ability to maintain a shallow thread depth relative to their longer lead distance. Another design advantage of a multi-start thread is that more contact surface is engaged in a single thread rotation. A common example is a cap on a plastic water bottle.
    Quote Originally Posted by LexD View Post
    Multi Start thread is the correct terminology, whether it is 2,3,4 or whatever number of starts, the thread itself can have only one lead. Multi lead seems to be a term used mainly in the USA. Yes but then you calculate that lead for multi start threads.
    If you can firm up definitions it can be good. A screw can have only 1 pitch = the distance from one thread to the next. Lead = the advance of the tool or the nut so for single start threads (default) the lead = pitch

    Multi start is the correct term used when a longer lead is desired for each revolution. As referenced below by AJ Chapman (a proper British chap), on 3 starts you’ll find 2 threads in between the one you’re cutting → so pitch is (1)P and lead is (3)P. You gear it to make the lead then arrange the 3 starts by properly indexing gears, part or using the compound.

    I just so LOVE his use of fractions in engineering for the shop. Things can be done with a divider & scale that cannot be done with a calculator (division is a real mean tart sometimes…).

    Good luck,
    Matt
    Attached Thumbnails Attached Thumbnails ajchapman_vol2_multistart_threads_pg107.jpg   ajchapman_vol2_multistart_threads_pg108.jpg   ajchapman_vol2_multistart_threads_pg109.jpg  

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    Quote Originally Posted by CBlair View Post
    Gordon, I know the pamphlet I linked to is geared toward you buying the tool from Starrett. But it might be helpful to others. I have another one that goes into much more detail but dont have a way to share it. One day I might get a scanner. Have a great holiday, I still love the caliper tension tool I got from you, it really works.

    Charles
    Charles, I have no objection to any specific brand being named or mentioned IF it is from personal use and experience. I'd love to have someone that works for a "big name company" to post in here with "inside" information.

    50 years ago Starrett was a very popular tool company here. I don't know why but sales just seemed to dwindle over the years. Maybe too much competition from European and Japanese companies? Does anyone know how much Starrett still makes themselves and in the USA? The best (and most expensive) Starrett thing I've ever used was a large profile projector. Much admired and used by many.

    Even although there still seems to be many brand names around it might surprise some how many are in fact owned by just one company.

    Gordon

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    Quote Originally Posted by Matt_Maguire View Post
    If you can firm up definitions it can be good. A screw can have only 1 pitch = the distance from one thread to the next. Lead = the advance of the tool or the nut so for single start threads (default) the lead = pitch

    Multi start is the correct term used when a longer lead is desired for each revolution.

    Matt
    Correct, and considering that this thread is in the Metrology section I would have thought that using correct terminology would be very important but it seems that in the US, at least, some "bastardization" of terms is accepted.

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    Quote Originally Posted by LexD View Post
    Correct, and considering that this thread is in the Metrology section I would have thought that using correct terminology would be very important but it seems that in the US, at least, some "bastardization" of terms is accepted.
    Maybe worth remembering that PracticalMachinist is owned by an American as is the majority of members.

    No worries mate


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