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  1. #13
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    Re: Tips for straighter bores

    I still disagree with you...…....end of topic.
    Ian.

  2. #14
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    Re: Tips for straighter bores

    look handlewanker, you are right, is not ok to check with another gauge, is not common behaviour

    also, future perspective, is hard, when it comes to find good workers

    there are still places with a high level of experimented people; some places still have 1:1departments, other are 1:3 or 1:5; such things are pretty high, but i don't know for long

    average is below 1:10, or 1:30, and this is an average from 30 yrs ago

    what i had been talking about is not common, since shops tend to be sporadic, but there are still places that are centralized



    ok, let's say that you have hundreds of gauges at hundreds of people ... how do you check them ?
    Ladyhawke - My Delirium, https://www.youtube.com/watch?v=X_bFO1SNRZg

  3. #15
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    Re: Tips for straighter bores

    Who cares!! The OP never even mentioned the tolerance of the bore he is working on. He only said that he is using gauge pins to check the hole and could tell the interpolated bore was tapered. A gauge pin may be just fine depending on the tolerance requirements. He simply asked how to take care of the taper.

  4. #16
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    Re: Tips for straighter bores

    This time I disagree with most posts.

    We did not get original posters d/l tolerances .. which are what it is all about.
    And size, depth, speed, qty goals.

    A reamer will deliver a hole about 0.01 mm in size, or a bit better, and mostly follow the bore while improving it a bit in straightness.
    Carbide reamers will make the hole straighter, and double-reaming will make the hole straighter and more uniform.

    Typical holes made with boring heads or modern vmc machines will have 0.01-0.02 mm tir/taper, to 0.04 mm (weak) bore sizes and straightnesses in the normal 1-3-4 d/l ratios.

  5. #17
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    Re: Tips for straighter bores

    LOL....a veritable storm in a tea cup...…...the problem I highlighted arose form the ongoing conversation/post.....whatever...…..and concerned the aspect of a customer supplier relationship when it comes to producing work to a customer's toleranced drawing., so I suppose it doesn't matter if the hole is not to the tolerance as long as it's parallel.

    As long as the gauge pin, no matter what size it is, goes into the hole it will as you say tell you if the hole is tight at the bottom…….I can't imagine what you would make of it if the hole was tight at the top and oversize at the bottom.
    Ian.

  6. #18
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    Re: Tips for straighter bores

    LOL....a veritable storm in a tea cup...…
    hello, yup, i started it i just remembered that a while ago, there was a calibration loss near the limit tolerance ... whatever, like you said, agreing with the client on control method helps

    so I suppose it doesn't matter if the hole is not to the tolerance as long as it's parallel
    i don't understand this

    I can't imagine what you would make of it if the hole was tight at the top and oversize at the bottom
    sometimes this happens ... for example part is controlled inside the machine and is ok, but after it is taken out, sometimes it happens to be oversized at the bottom

    most common cause, is that the fixture puts too much pressure on the part, & the part changes shape

    a quick way to check it, is to leave the gauge inside the part, and take the part out : if the gauge does not slip as easy/hard as when the part was inside, or, if the gauge is blocked, than few adjustemnts are made

    this is "fluaj", i don't know the english word, rigid material that leaks slowly; unpleasant situation is when this phenomen has effect spread across a time period greater than fewhours-1-2 days

    to fix this, it may be enough to program a taper, or to reduce fixture forces, stabilize internal part tension through prior heat-treatments, etc / kindly
    Ladyhawke - My Delirium, https://www.youtube.com/watch?v=X_bFO1SNRZg

  7. #19
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    Re: Tips for straighter bores

    Lol jesus you guys went off into the weeds. Ok all I'm asking is that say you're milling a .125" hole, or maybe some weird size where you can't just run a reamer through the hole so you have to bore it out with an endmill, or its too small for boring head. And you have a close tolerance to hit, whatever say it's a press fit and it needs to be +- .0002". If, when checking with a gauge pin from a set with .0001 increments, a .1248 only goes maybe halfway into the hole depth its milling to, indicating a taper in said hole, and when you comp the tool on the cnc machine still get an equivalent taper, what are some good tricks to mill straighter holes.

    Sent from my SM-G950U using Tapatalk

  8. #20
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    Re: Tips for straighter bores

    JS......I think you missed the part where I said......You cannot enter a 20mm diam hole with a 20mm diam pin.....that is a press fit or as we commonly say a size for size press fit.

    Go back and read the thread and see where the go-no go gauge application applies.

    LOL....and you want to "bore" a .125" diam hole with an end mill....by helical interpolation....LOL...... to a +- .0002" tolerance????….you will get an odd ball size for sure.

    Your eventual question regarding "good tricks" to make good holes...…...there are no good tricks...….you need skill and experience to make good holes......good machinery also helps.

    A hole that is not a standard size and is relatively small in diam would have to be bored with a boring head or a specially ground undersize reamer....or perhaps an adjustable reamer, but hitting the +- .0002" tolerance would be very tricky to say the least.

    BTW.....if the job volume is not sufficient to cover the cost involved in getting a hole to such a tight limit....give it away and move onto more profitable work.....you have to know when to fold them, know when to hold them and know when to walk away etc etc.
    Ian.

  9. #21
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    Re: Tips for straighter bores

    Quote Originally Posted by JOHNSMITTY View Post
    what are some good tricks to mill straighter holes
    hy john, there are a few tips spread across a few posts, but i also started a bit of off-topic conversation, making it hard for you to spot what you needed, so here it is :
    ... all ok until post 5 inclusive
    ... post 16 is ok

    other tips :
    ... lower feeds, because higher feeds will mess the cilindricity
    ... low overhang
    ... "through hole + vertical reamer" is better than " blind hole + horizontal reamer "
    ... a toolholder with tir adjustment
    ... using a shorter go gauge, because longer ones require improved cilindricity
    * in the end, is all about tolerances

    this is all i can think of now / kindly
    Ladyhawke - My Delirium, https://www.youtube.com/watch?v=X_bFO1SNRZg

  10. #22
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    Re: Tips for straighter bores

    Just as Ian said, use a boring head to ensure cylindricity. If is a single part or a small batch I´d rather use a holtest micrometer to measure the bore.

    Greeting

    Ari

    Quote Originally Posted by handlewanker View Post
    Use a boring head set to size for the final pass.
    Ian.

  11. #23
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    Re: Tips for straighter bores

    hello, about reaming / cilindricity, etc, this is a pretty common thing; truth is that is much easier and reliable only to drill, while reaming may take longer

    is ok to rough, is ok to finish, but is less productive to debur or ream ... so there are operations that are more productive than others, and a cnc which runs non-productive operations is less-profitable; this does not mean that it is not profitable

    from this consideration, some shops avoid reaming operations on the cnc's; simply, because it is not productive, at least on small batches

    so, is about some shades of gray / how do you believe that is organised such a shop that does not ream on the cnc ? kindly
    Ladyhawke - My Delirium, https://www.youtube.com/watch?v=X_bFO1SNRZg

  12. #24
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    Re: Tips for straighter bores

    A reamer is an all time standard tool to produce holes quickly to size time and again...…..if you resort to just boring a hole with a boring head it will take longer even if it is a superior straight round and to size hole...…...in production time is money and a reamer will save time every time.

    That would be my first go to tool for a hole solution...…...alternatives go down the more time and less accuracy ladder.

    You can take a standard to size reamer and regrind it to suit your drawing tolerance if the drawing requires a non standard size etc......for low volume work, say 3 or four parts then an adjustable reamer or a boring head will do the trick as they're infinitely adjustable.

    I cannot imagine why a CNC situation requires a different approach.

    BTW....before I retired, when I was still employed as a production planner, I tooled the CNC's with carbide tipped reamers every time......this was back in 1990 - 2000 era....have things changed since then?

    It may be quicker to just drill a hole but a drill won't cut to a tight tolerance size, give a good finish or be on position.

    Reaming after drilling also is not an answer as the reamer will just follow the drilled hole and that can be out of position...…….the proper sequence must be followed if you want to get work that passes inspection both for size, finish and positioning......but pigs can fly too under certain conditions.

    Deburring can be done with a vibro finishing machine or a tumbler.
    Ian.

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