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  1. #21
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    Quote Originally Posted by michiganbuck View Post
    QT: Any thoughts or tips would be appreciated.

    You want to feel your bit/insert into your fish gauge, to the side of the part.
    also feel the bit /insert into the fish gauge to know it's angle is correct....


    LATHE fish gauGeCHECKIG a pART. PHOTO - Google Search
    I have not used a fish gage in decades. Can you still buy them? They are also very useful for getting your tool tip on center.

  2. #22
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    Quote Originally Posted by Gobo View Post
    I have not used a fish gage in decades. Can you still buy them? They are also very useful for getting your tool tip on center.
    And for checking a center point you maigh need to turn on your lathe.
    6deg Angle, Stainless Steel Center Gage 6597785 - MSC

  3. #23
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    Quote Originally Posted by michiganbuck View Post
    Thank you, I understand you're trying to cover all the bases with basics first.
    Yet I already did all that many years ago when I was machining parts out of teflon, stainless and hastalloy for an R&D dept.
    Just didn't know why I was getting buggered right side threads all of a sudden recently after setting everything up theoretically as it should be.
    Was wondering if I came down with a case of CRS and missed something ya know.
    Like Maybe I wasn't using high sulphur chlorinated cutting oil when Energy Release worked fine before... or some simple thing as that.
    Maybe I didn't lock down the quick change toolholder...lol I've done that once or twice.
    But no, I checked this time.
    My angle was not acute enough even though everything showed 29 to 29.5 degrees.
    I simply went to 25 deg as a test run first and if that didn't work I would have went to 20 deg.
    25 worked fine, perhaps 27 would maybe even 28.
    Although for my setup, when machining A2 drill rod...29.5 does not work on this tough of steel

  4. #24
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    Don't know what you mean by "deflection" in your posts. If you mean that the work is deflecting, due to tool pressure, too much then you need to support your work better (less over hang out of the chuck or collet or support the work with tailstock, steady rest or follow rest.) Or perhaps you mean the tool itself is deflecting in which case you need a more rigid tool setup.

    On the other hand... if you mean be "deflection" the angle between the compound feed axis and the face of the chuck (normal to the axis of the work) then 29.5 deg is correct. Some like 30, some like 29, some like none at all and set it to 0 and plunge straight in. 25 degrees is not correct but you can probably get away with it. May not have the best finish on the left flank of the thread though.

    Getting the correct thread form or shape should be the easy part on a lathe. Also getting the correct pitch is easy. The difficult part is getting the correct pitch diameter. Sometimes it is also difficult to get a good finish. Finish depends on a whole host of factors depending on material, tooling and speeds.

    -DU-

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  6. #25
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    Well at first I thought maybe the tip chipped and the thing was wandering to the left side.
    The left side cut itself would look normal while of course then the right side would show the wander.
    But the tip was fine and still sharp.
    Main question was, why if set at 29.5 would I get the result I got.
    Perhaps dirty leadscrew or play in the halfnut?
    I cleaned the leadscrew before hand though.
    I simply went from 29.5 to 25 as a process of elimination to gauge the result.
    28 deg may have gotten the same result, 27 , 26.
    But I went to 25 simply to rule out and see if my angle just wasn't acute enough.
    I understand 29.5 should work. 29 should work.
    I have also read people set it at anywhere between 30 and 0
    30 being not desireable in case of carriage slop and wandering while feeding.
    So they go to 29.5 to make sure at least a slight cut is made on the right side of the toolbit.
    The thing is....all the diehards say 29.5 because that's what they've been taught but haven't thought past what they've been taught b ecause thats just the way ya do it.
    what does it matter whether it is anywhere between 0 and 29.5 deg within the whole scheme of things if the net result is the same?
    Not a newbie question.
    Yes 29.5 degrees...a hear ya all
    So gents, What sets the degree the compound is set at
    .....as gospel?
    If one can plunge straight in at 0 why not even 15 deg?
    Net result is the same...I'm paying for the toolbits...the sky didn't fall...
    so now what...
    So as a process of elimination instead of advancing my compound at 1/2 degree increments and wasting a bunch of time and material I instead decide to set the angle to 25 to rule out the fact my 29.5 may not be an actual 29.5
    Everyone understand why now?

    By deflection the first pic shown appears as if the tip of the cutter is deflecting off the right side of the thread....when set at 29.5 from perpendicular to the face of the chuck.
    Or even i could have been at 30 or 30.2 or whatever...even though everything showed 29.3 actually to be precise.
    I'll show again the net result...threads look fine to me now.
    Everyone notice the relief I cut first on the left side....is the same diameter as the finished thread minor diameter?
    Anyone object to the finish and form of the threads pictured here?
    If I continue to cut at 25 degrees and the net result is the threads look like this picture would you know if I didn't tell you?
    All the elitists thinking everyone needs to own a Hardinge to be part of the club, calm down man.
    Agreed, pitch diameter of key importance. Which is why I calculate the amount needed to be turned.
    turn a practice part or two
    then check fit then and write down the advancement needed on the compound to achieve this fit.
    in this case .001" short of a line fit.
    20190110_130813.jpg

  7. #26
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    There is no magic to the 29* or 29.5* setting on the compound. The purpose of feeding the compound at an angle is to have most of the cutting on the leading edge of the tool. That avoids having chips from both flanks impinging on each other. The compound is set at slightly less than 30* is so the trailing edge of the tool takes a very light cut to avoid "steps" in the trailing flank of the thread.

    There are those who advocate plunge cutting the thread. I, personally, do not care for it.

  8. #27
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    Illinoyance....well said thank you and exactly my point....there is no magic to the angle.

    The purpose is to relieve stress off the tool and majority of chip flow is on the Leading (left) side.
    I'm not re-inventing the wheel suggesting 25 degrees should be the new magic number.
    Just that....in this case
    even at 25 degrees....majority is still on left side with less stress on right side...correct?
    still less stress than a 0 degree plunge cut.
    I personally do not want to plunge cut into hard tough steel neither.
    Does everyone else understand?

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    25 degrees should Not be the new magic number. It is not a big deal but still it is wrong and so a poor practice.

    Until you see that I forbid you to work on a customer's barrel. Just kidding, or not.

    The thread bit or insert has to be dead centered like 30 30 to the work and that is made that way with the fish gauge..
    You cant/should not risk a one-up like a $100 barrel risking the bit/insert is not square with the part..
    Perhaps they sent you the wrong insert/perhaps there is a chip in the holder / it is just not worth the risk of failing the valuable part with not knowing for sure the bit/insert is not square with the part.. INHO.

    Simple rules and procedures make quality machining work...

    If you read how to run a lathe it recommends a positive rake for steel , at 29 , 29 1/2 or 30* compound (all ok). The positive rake is easing the flow of the cutting action to the left edge of the tool bit cutting edge when the travel is going to the right toward the head stock..... With the likes of a chip breaker insert it allows the cutting action on only one side and the other side goes down the angle with not making steps .... Agree on a CNC lathe one can program a shave on the left and then a shave on the right edge ..but one can not/ does not do that on a manual lathe.
    Cutting threads is a simple piece of cake and yet so many have problems because they just don't follow the drill.

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  11. #29
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    It's hard to say what happened. The first thread you posted a picture of surely looks as if the tool was feeding in at 60 degrees, instead of 30, which is why people suggested that your compound marking might be "backwards" from what you thought.

    The difference between that infeed angle and the one in your second, "good" thread, is definitely much more than 4 or 5 degrees.

    So we have to believe that something was being deflected an awful lot in that first thread, and then magically stopped deflecting when you fed "straighter in".

    I don't see it happening that way...

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  13. #30
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    compound angle doesn't mean squat if the tool tip is not perpendicular to the work.
    sound like the case here.

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    Actually the view in post #1 does not even look like a 60* thread how can that be?.. perhaps the part is not setting square on the comparator table... it should be a 60* even if the bit was wrong angle set to 20* 40*

    But the view shows 30 45... that could only be done with a 75* point...so i blame the view...

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    Quote Originally Posted by michiganbuck View Post
    Actually the view in post #1 does not even look like a 60* thread how can that be?.. perhaps the part is not setting square on the comparator table... it should be a 60* even if the bit was wrong angle set to 20* 40*

    But the view shows 30 45... that could only be done with a 75* point...so i blame the view...
    Hmmm, that's not really the case.

    Imagine if a proper 60 degree threading tool was squared properly to the work, but the infeed was nearly parallel to the Z axis and the work. The resulting thread would have a very large angle on the right flank, and a proper 30 degree angle on the left flank. This would be true for any infeed angle greater than 30 degrees. In this case, there would never be any cutting taking place on the right flank.

    Now, if the tool was fed in at an angle closer to perpendicular to the work and the Z axis, an angle smaller than 30 degrees, then the resultant thread profile WOULD match the profile of the tool, as it would be cutting on both flanks all the time.

  16. #33
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    NO, NO, NO!

    NOT 59 degrees or even 59.5 degrees. That will also produce a smaller error, but an error non-the-less. It will just be harder to see. One flank of the thread that is cut will have a 31 degree angle and some jogs in it instead of the proper 30 degree, straight flank.

    90 deg - 29.5 deg = 60.5 degrees. And that is where you set it if the scale has it's zero when the compound is moving parallel to the main lathe axis. 60.5 not 59.5.

    Looking at another way it is 29.5 degrees from the 90 degree mark on those lathes.

    I thought it was bad when you guys didn't understand elementary trig., but first grade arithmetic? Jeeeesh!



    Quote Originally Posted by kenton View Post
    I agree, the machines at the community college I went to and was a classroom assistant at had the numbering laid out so you set the compound to 59 degrees. I saw a lot of threads that looked just like that from people who ignored the teachers instructions and set their compound to 29 degrees like it said in the book.

    In hindsight it was a very good learning experience for everyone involved, if not rather frustrating.

    EDIT: already covered, I'm a slow typist.

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  18. #34
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    ya..and don't trust the scale on the machine unless you verify it.
    might be off a degree or a few.
    sometimes you have to make a new witness mark for zero.

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    Quote Originally Posted by awander View Post
    Hmmm, that's not really the case.

    Imagine if a proper 60 degree threading tool was squared properly to the work, but the infeed was nearly parallel to the Z axis and the work. The resulting thread would have a very large angle on the right flank, and a proper 30 degree angle on the left flank. This would be true for any infeed angle greater than 30 degrees. In this case, there would never be any cutting taking place on the right flank.

    Now, if the tool was fed in at an angle closer to perpendicular to the work and the Z axis, an angle smaller than 30 degrees, then the resultant thread profile WOULD match the profile of the tool, as it would be cutting on both flanks all the time.
    agree .. With swinging and additional 15 degrees one would get 45 on one side...
    So back to what is said back in post #7 good to look over a protractor to see a/about 29 - 30* to then know how your compound is numbered.

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    It’s not the angle of the compound or deflection in your tooling that caused that. I would be willing to bet that you engaged the lead screw on the wrong position. Gotta watch that thread clock carefully. On most lathes (at least every one that I have ever used), certain thread pitches will thread properly on all positions, where other pitches require you to engage on specific clock positions to ensure you are following the position of the previous cut. It’s not hard to accidentally miss and catch the wrong position, thereby cutting a double thread. Looks like you did that about halfway through.

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  23. #37
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    When using a carbide insert threading tool I dispense with the fish gauge. Getting the shank parallel with the face of the chuck is good enough. For hand ground threading tools I always use the fish gauge.

    My on-edge inserts are zero rake as are most of my hand ground tools. I have tried some side rake on some off my hand ground tools and find it works quite well, especially in gummy steels.
    I want to try on-edge inserts with positive rake but haven't gotten around to it.

    To adjust my hand ground tools to match the thread pitch I grind them sharp then stone the required flat on the end.

    I haven't used laydown inserts much but it looks like there is positive rake formed into the insert. I would use full profile inserts if I could but most vendors require buying them in lots of 10. Shars will sell single inserts. That makes it practical to use full profile inserts.

    I have a number Acme threading tools, all hand ground. For those I set the compound for 1/2* less than the flank angle. For these tools I ALWAYS use the Acme thread gauge when grinding the tool and when setting it in the lathe.

    I realize that some lathes vary in how the compound angle graduations are set up. Forget what the actual numbers say and set the compound at the thread flank angle less about 1/2*.

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    im sure I will get flack for this...

    I don't get the HSS insert thing...if you are going to pay high quality carbide insert price why not use carbide inserts?
    strength of HSS is utilty and affordability.
    strength of carbide insert is convenience and repeatabiltiy.

    seems like all the cons without much pros.

    someone is going to say you can resharpen them by rubbing the face, but I'm not buying it...the flanks are going to see some wear too.
    and you got no chip breakers either.

    these are great BTW-
    LAYDOWN THREADING TOOL

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  26. #39
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    Quote Originally Posted by iwananew10K View Post

    these are great BTW-
    LAYDOWN THREADING TOOL
    Yes they are.

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    Why HSS? At the speeds most people are able to thread HSS is a suitable tool. There is no need for the heat resistance of carbide. It is easy to touch up the edges of the HSS tool and saves the expense of the carbide insert. With a bit of regrinding I can change the flat on the end of the tool to suit any thread pitch. I can also add top rake or side rake to improve cutting conditions.

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