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Relative newbie question on internal threading?

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  • MattiJ
    replied
    I think you need to describe your method bit more. What ID and OD diameters you are using before you start threading? What do you use as a reference for setting the tool starting position? Light touch to workpiece turned to nominal diameter?
    Or do you start with ~0.05mm oversize stock and let the full form insert do its work and keep cutting until you end up with correct OD/ID ?

    I have never actually used full thread form inserts but AFAIK you can start with oversize stock and keep cutting until you end up with desired major diameter?

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  • J Tiers
    replied
    Obviously you are aware of the "double depth of thread" tables, that allow you to get to the general infeed amount.

    For inside threads there is no good simple way to measure other than a go-nogo gage for the thread type. You can also section a sample part, and check it on an optical comparator, but that is a bit impractical for most HSM uses. Usually HSM folks use a mating threaded part as a "go" gage, and stop when it enters the threads properly.

    As for getting the angle correct, you can set the boring bar or holder in line with the lathe axis, which should set the cutter in proper perpendicular position. If you are using a full form cutter, presumably it is a commercial one, and if used in its proper holder, is suitably aligned if the holder is. That you can measure with an indicator as you move the carriage.

    If that is not going to do it, maybe a picture of the setup is needed.

    The feed per pass is dependent on the thread size, the setup, the material, the machine itself, the cutter, etc. I do not think any number can be given. A large thread on a small machine takes more passes, just due to material removal.

    What size thread is your typical work? What is the machine? in what material?

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  • Shawnba67
    replied
    Well, good set up +proper procedure=good part. My lathe is manual. I Think that I have my tools set up correctly (fishtail guage) however I have no better idea on how to criticaly QC than to see if my procedure matchs somekind of standard . The cut til it fits really isnt useful here. If my cutter is off perpindicular then my threads will need to be oversize to fit.The fit will feel good but the threads will be weaker. I have no way/knowledge of how to verify true(fishtail guage does not inspire confidence)oo perpindicular of my thread tool. However if my infeed matchs what most are ending up with my set up is likely correct.

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  • Mcgyver
    replied
    Originally posted by Shawnba67 View Post
    How many thousanths (.001's) infeed does it normally take to get from male piece starting in the internal almost a full turn to acheiving a better than hardware store fit but easily threaded in with fingers? My attempts seem to take more infeed than I feel like they should. I use full profile bits for both int/ext.
    I am troubleshooting my setup. But without knowing what the norm is Im a little behind the curve.
    To keep to my question I AM NOT asking about calculating infeeds. .708 x tpi or what not. Specifically asking about the amount of infeed from 1 turn in to finished thread. So I can compare to my situation and then evaluate if Im doing it right. Or if my set up is lacking. Thank you
    its hard to know how close you are, one turn in is not a thing, i could take more passes than you might think or take one or two. Sneak up on it a thou DOC at a time until it threads the way you want it to.

    If you want something with more a correct procedure to it, say you need to make a part to tolerance make a part to fit some commercial part, you need to measure, and as always, there's a range of tolerances governing things.

    Leave a comment:


  • Shawnba67
    started a topic Relative newbie question on internal threading?

    Relative newbie question on internal threading?

    How many thousanths (.001's) infeed does it normally take to get from male piece starting in the internal almost a full turn to acheiving a better than hardware store fit but easily threaded in with fingers? My attempts seem to take more infeed than I feel like they should. I use full profile bits for both int/ext.
    I am troubleshooting my setup. But without knowing what the norm is Im a little behind the curve.
    To keep to my question I AM NOT asking about calculating infeeds. .708 x tpi or what not. Specifically asking about the amount of infeed from 1 turn in to finished thread. So I can compare to my situation and then evaluate if Im doing it right. Or if my set up is lacking. Thank you
    Last edited by Shawnba67; 12-10-2017, 09:57 AM.
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