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  • eKretz
    replied
    Originally posted by old mart View Post
    Using an endmill to finish a hole is always hit and miss, I would always go for the increased stiffness of solid carbide, and ideally a test made before the final go. The recent holes I made were on the lathe, and even a different chuck in the tailstock might have influenced the outcome. The 1/4" hole required going in the full length of the mills flutes, and I withdrew it to clear the swarf several times, and there was some indication of cutting as the cutter was withdrawn each time. Maybe I should have used tapping oil instead of dry.
    When I was working as a fitter in the manufacture of aircraft components, I did a lot of reaming to fairly tight tolerances (typically +- 0.0005"), and there were ways of making the same reamer cut quite different sizes if you knew the tricks.
    It is not remotely surprising that your hole was oversize if you did it in the lathe with a drill chuck. This is not what I thought the question in the OP asked, either. I had supposed he meant to do this in the mill, where runout can be checked. If the cutter is not running true, it will cut oversize... The same goes for the lathe, except now true means that you need the cutter dead on center, and the axis of the endmill must be true and concentric to the lathe headstock bearings' centerline. If the cutter is not on center and straight, guess what happens? The fact that your cutter was rubbing on the way out of the hole should have been an instant indication to you that it was either very dull or not on center. I have never had this act in a "hit or miss" fashion when I've done it, save maybe ½ thou or so. You need to know your machines and plan ahead; ensure that everything is optimal to get a good result. The fact that the cutter has clearance and can cut on the side has nothing to do with this working or not. If that was a problem, boring would not work at all. Effectively, when using this approach you are turning the endmill into a multi flute miniature boring head.

    Amen Doozer.
    Last edited by eKretz; 08-07-2021, 01:57 AM.

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  • nickel-city-fab
    replied
    You too?? Wow I thought I was the only one who notice.
    Thanks!
    Although I reached a different conclusion.
    I think that
    Most all of the issues boil down to Pride.
    Or lack of humility.

    I always ask myself, "Where does a person get their self-esteem from?"
    If they are getting it from the wrong place, then there will be trouble.
    When you know where somebody gets their self-esteem from,
    then you will have the keys to that person.

    For me, the answer is in Religion.
    But we're not allowed to discuss that here (for obvious reasons)
    Nobody teaches it as a practical way of life any more.
    I don't always live up to my own ideals, but at least I have some.

    I agree about attitudes, but I think the reason why they offshored everything is simple Greed.
    And a distinct case of Pride that says it is no longer good enough to make 20x more than the Workers.



    Originally posted by Doozer View Post

    Right on.
    ...........
    The education system is constantly
    being dumbed down and people are not being thought how to think,
    yet they behave like they know it all. This, instead of actually being
    taught real things. See that self protection and preservation mechanism
    kicking in again? This all needs to change. No one teaches cause
    and effect relationships. No one talks about how to get along with
    others. No one talks about manors and how to treat other people.
    No one talks about mental health and how to have self perspective.
    So even to get an answer to a simple machining question is quite
    troublesome.

    --Doozer

    Leave a comment:


  • old mart
    replied
    Using an endmill to finish a hole is always hit and miss, I would always go for the increased stiffness of solid carbide, and ideally a test made before the final go. The recent holes I made were on the lathe, and even a different chuck in the tailstock might have influenced the outcome. The 1/4" hole required going in the full length of the mills flutes, and I withdrew it to clear the swarf several times, and there was some indication of cutting as the cutter was withdrawn each time. Maybe I should have used tapping oil instead of dry.
    When I was working as a fitter in the manufacture of aircraft components, I did a lot of reaming to fairly tight tolerances (typically +- 0.0005"), and there were ways of making the same reamer cut quite different sizes if you knew the tricks.
    Last edited by old mart; 08-06-2021, 03:03 PM.

    Leave a comment:


  • Doozer
    replied
    Originally posted by tomato coupe View Post

    Nonsense. I happened to do this last night -- a 3/16" (.1875") 2-flute end mill resulted in a hole that took a .187" pin gage but not a .188" pin gage.

    Right on.
    The problem here is there are people with different machines
    that will give different results. Think machine capability.
    Then you have the people using these machines with various
    levels of skill, and different minds, which may or may not be
    willing to learn or equally so, may not be willing to accept that
    they don't know it all. Think process capability.

    So you could have a jig borer and an experienced operator
    and get great results.
    You could have a jig borer and a novice operator, and get
    poor results.
    You could have a China mill and an experienced operator
    and get good results.
    You could have a China mill and a novice operator, and get
    poor results.

    It all just depends. The biggest hurtle to answering this question
    is ego. You have machinists, either hobby or professional, that
    may or may not have the skills or machine to be able to use an
    end mill to cut on size by controlling all the variables. It can be
    done, but many refuse to believe it. Many have the attitude (ego)
    that think, if they can not do it, it can't be done. Then they assert
    that as fact. They assert their notion as fact because it is a mental
    protection mechanism for them that allows them a sense of
    superiority at all times. The reasons for this vary, but it is usually
    a spoil of the school system in the US that drills into children that
    they must be right and have the right answer all the time. So you
    have a society of people, when asked a question to which they
    do not have the right answer, resort to making up something, just
    because they feel put on the spot to answer the question. They
    usually give some vague or ambiguous response, just because
    they want to save embarrassment for not knowing the answer.
    Others just make something up and defend their position with
    confusion nonsense. So here we have, "No, and end mill will always
    cut oversize". It is a societal problem that we get so many answers
    like this. It is a mental health problem and an education problem with
    our schools and the curriculum. So because of this, we have a bunch
    of people that constantly have a personality conflict with their peers.
    Poor communication. Poor productivity. Everyone thinks they are
    smarter than everyone else above them on the social ladder.
    No wonder there are so many homicides in the workplace in the US.
    People here are an aggravating bunch that constantly argue when
    asked to do something. Or else they do subversive things quietly
    instead of arguing. Things need to change. No wonder manufactures
    chose to offshore manufacturing in this country. It is because here
    we have a people problem. The education system is constantly
    being dumbed down and people are not being thought how to think,
    yet they behave like they know it all. This, instead of actually being
    taught real things. See that self protection and preservation mechanism
    kicking in again? This all needs to change. No one teaches cause
    and effect relationships. No one talks about how to get along with
    others. No one talks about manors and how to treat other people.
    No one talks about mental health and how to have self perspective.
    So even to get an answer to a simple machining question is quite
    troublesome.

    --Doozer

    Leave a comment:


  • old mart
    replied
    Yesterday, I wanted a blind 1/4" hole in steel, and drilled to 6mm with a solid carbide drill, and then finished with a 1/4" solid carbide endmill. The hole was 0.2515" diameter. The endmill was kindly given to me with others and a wrist pin by NSF.

    Leave a comment:


  • tomato coupe
    replied
    Originally posted by Toolguy View Post
    Using an end mill as a drill will always make the hole oversize.
    Nonsense. I happened to do this last night -- a 3/16" (.1875") 2-flute end mill resulted in a hole that took a .187" pin gage but not a .188" pin gage.

    Leave a comment:


  • nickel-city-fab
    replied
    Originally posted by Doozer View Post

    Yep. If you don't believe it, test it.

    -D
    Yeah, I actually did that. Once. And only once.
    Then I got smart, waited till I has some $$$
    Bought a bunch of reamers

    Leave a comment:


  • Doozer
    replied
    Originally posted by eKretz View Post
    ... Go plunge a hole from the solid using a center cutting endmill with all your table clamps unlocked and tell me there are no side forces involved... Or if you're feeling particularly brave, try it in a drill press with a floating vise...
    Yep. If you don't believe it, test it.

    -D

    Leave a comment:


  • Toolguy
    replied
    Although I don't like an end mill for drilling holes, I have found that a ball end mill seems to work better than a square end mill for through holes. The cutting action seems more gentle and controlled. YMMV.

    Leave a comment:


  • eKretz
    replied
    Originally posted by Paul Alciatore View Post
    I am not 100% sure about what you are asking, but my experience and instinct says that if the cutting edges of the end mill are at a right angle to the axis, then they will not pull either in or out so there will be no tendency for the end mill to go off axis. It is the angle of the drill bit's cutting edges that rotates the force vector at an angle and then, if the two edges are cutting different width chips, then the one with the larger chip will experience the larger force. And with the two forces (from the two edges) pointing inward, the larger one will move the drill bit in the opposite direction.

    Since the cutting edges of a flat, end cutting, end mill are perpendicular to the axis, the forces they experience are also parallel to the axis and there is NO component of the force vectors that points toward the center or to the outside. So there can not be any net force in any direction other than axial (parallel to the axis of the end mill). It will cut straight even if one edge is cutting all along it's length and the other one is completely in air.

    All end cutting, CENTER cutting end mills that I have seen have one cutting edge that goes from the OD all the way to the center and the other cutting edge(s) stop short of the center. In other words, they all are made with different lengths. That is just the way they are made. And none of them pull to one side or toward one of the cutting edges.

    No. I'm sorry but that is all wrong. Yet another example of theoretical blah that doesn't apply to real world usage. Go plunge a hole from the solid using a center cutting endmill with all your table clamps unlocked and tell me there are no side forces involved... Or if you're feeling particularly brave, try it in a drill press with a floating vise. Most of the time, what you're going to end up with is a vise wallowing around and an oversized - and likely out-of-round - hole.

    And have you seen a lot of 2-flute center cutting endmills that have unequal length flutes? Not every multi-flute endmill has one long flute. Some manufacturers go that route, some don't. What you're also forgetting is that end mills do NOT have square ends - they are hollow in center, or rather ground with clearance so the center doesn't rub - though that doesn't make much if any difference in this case.

    Additionally, endmills and milling machines are never perfect, there is always one flute a little longer than the other and/or some small amount of runout. The flute that cuts first or heaviest will pull the cutter or table around. Minimize the stock being removed and you minimize those forces.
    Last edited by eKretz; 08-04-2021, 08:40 AM.

    Leave a comment:


  • Paul Alciatore
    replied
    I am not 100% sure about what you are asking, but my experience and instinct says that if the cutting edges of the end mill are at a right angle to the axis, then they will not pull either in or out so there will be no tendency for the end mill to go off axis. It is the angle of the drill bit's cutting edges that rotates the force vector at an angle and then, if the two edges are cutting different width chips, then the one with the larger chip will experience the larger force. And with the two forces (from the two edges) pointing inward, the larger one will move the drill bit in the opposite direction.

    Since the cutting edges of a flat, end cutting, end mill are perpendicular to the axis, the forces they experience are also parallel to the axis and there is NO component of the force vectors that points toward the center or to the outside. So there can not be any net force in any direction other than axial (parallel to the axis of the end mill). It will cut straight even if one edge is cutting all along it's length and the other one is completely in air.

    All end cutting, CENTER cutting end mills that I have seen have one cutting edge that goes from the OD all the way to the center and the other cutting edge(s) stop short of the center. In other words, they all are made with different lengths. That is just the way they are made. And none of them pull to one side or toward one of the cutting edges.



    Originally posted by Tundra Twin Track View Post
    Dumb question about the Endmills that don’t have equal length cutting edge for plunging through pilot hole,assuming just make pilot hole larger?
    Last edited by Paul Alciatore; 08-04-2021, 05:45 AM.

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  • eKretz
    replied
    Yes. Leave stock similar to that left for reaming or a bit more. The smaller the better in terms of causing any axial forces.

    Plunging directly in with no pilot hole is a good way to get an oblong hole. The larger the endmill, the more important this is. Cutting forces farther from center give the cutter more leverage to move things around.

    Leave a comment:


  • Tundra Twin Track
    replied
    Dumb question about the Endmills that don’t have equal length cutting edge for plunging through pilot hole,assuming just make pilot hole larger?

    Leave a comment:


  • Doozer
    replied
    Originally posted by Fasturn View Post
    Click image for larger version Name:	download.jpeg Views:	2 Size:	8.6 KB ID:	1954724
    I have a Sony on my B&S #13 cylindrical grinder, and it is a magnetic scale. Just a steel rod with
    I presume a sine wave magnetically recorded on to it. Someone with a forklift tore the reader out
    and I fixed it. I did not know Sony made glass scale units.
    I would like to buy a Sony for my SIP #4, but I might settle for a Newall.
    I choose not to afford a Heidenhain unit, even though it would be nice.

    -Doozer

    Leave a comment:


  • Doozer
    replied
    I currently own at least 3 machines that weigh 9,000 pounds each.
    Rigidity makes cuts come out accurate. One less variable to contend with.
    It is such a pleasure to make whatever you want, and have it come out
    as accurate as you desire. I know maybe you are thinking what I am
    saying is way overkill for a home shop, but it is such a joy to use my
    machines to make my projects.

    --Doozer

    Leave a comment:

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