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  1. #61
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    Quote Originally Posted by Mechanola View Post
    You are right, piercing takes longer.

    If possible, drill from both sides with short-clamped standard length two-flute bits. Then one pass through with a longer one. Size and better straightness with a three-flute tool. Take back feed rate, aim at 18 m/min Vc; 2000 rpm with 2,8 mm Ø drills. Or 59 sfm, 0.11" and 0.1180" dia tools
    Hello Mechanola,
    By the time you have carried out drilling from both sides (obviously requiring repositioning the part), the time will exceed the OP's current cycle time. If a longer drill is going to be used to size the hole, clearly the drill used from either side will have to be smaller. The OP is having trouble with a 3.0 diameter drill, so using a smaller drill is a retrograde step. Further, getting a small drilled hole to meet in the middle is a dubious process and the long drill will follow to some extent, irrespective of the number of flutes, any kink in the hole that may exist.



    Regards,

    Bill

  2. #62
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    Quote Originally Posted by Mechanola View Post
    You are right, piercing takes longer.

    If possible, drill from both sides with short-clamped standard length two-flute bits. Then one pass through with a longer one. Size and better straightness with a three-flute tool. Take back feed rate, aim at 18 m/min Vc; 2000 rpm with 2,8 mm Ø drills. Or 59 sfm, 0.11" and 0.1180" dia tools
    Drilling from both sides is out of the question. So I guess my only options are to push a shorter drill first & then follow it up with a longer drill & to try using a parabolic drill

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    Quote Originally Posted by bobbybrown23 View Post
    Drilling from both sides is out of the question. So I guess my only options are to push a shorter drill first & then follow it up with a longer drill & to try using a parabolic drill
    There are always more than one way to do a thing. Your original post was about "decreasing" cycle time.

    I would drill with a Stub length Drill, depending on condition, without a spot Drill.
    Then I would change to an extended length Drill (55mm)

    But the real cycle decrease will come from increased Spindle speed and appropriate chip load.

    R

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    We had success with a split point high quality HS parabolic drill, and with sharpening it before it got much of a wear land..smaller chips were pulled up and out with the fast spiral.

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    hss parabolic drills in general work at higher feeds than regular hss drill bits BUT they are more likely to break cause flutes are cut bigger to allow chips to come out easier and longer ones are more sensitive to .001" undersize pilot holes (long drills make bad reamers) and on curved holes they vibrate easily til they break.
    .
    i have had longer parabolic drill bits break just on shock of tool change. and have had them break just putting in a tool magazine pocket.
    .
    just noting after many thousands of holes drilled with parabolic drill bits the sudden tool failure statistical rate is definitely not zero. even 1 or 2% sudden tool failure can be very expensive (long parabolic drills often very expensive) and time consuming either getting broke drill out or remaking parts. and at higher feed rates and longer depths they often drift or drill curved holes. bottom of hole out of theoretical position. i often see 10" depth holes the bottom of holes is 0.100" out of position. when those holes are counterbore (part flipped) with a short spade drill to 9" depth most of the error is removed cause at the 1" depth parabolic holes drilled from other side is often within .004" position at 1" depth. holes are more curved at higher feeds rates in general. often reason hole drilled all the way through with parabolic drill is to let coolant get to drill tip easier when spade drill used. if no or little peck is used often drill tip is dry and hot

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    In fact, this is a deep-bore thing and deep boring is done with gun drills. High oil pressure is needed. I’m perfectly aware of the difference between conventional shop and specialised work. If you can farm out, do it.

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    I don't think 16xD is Gun Drilling territory JMO. It's deep but not DEEP. Most 3mm Jobber length Drill have 40mm flutes. But if you have a Gun Drill laying around, well shit yeah.

    Really this isn't a tough job, it's just figuring out how to go faster.

    R

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    Quote Originally Posted by litlerob1 View Post
    I don't think 16xD is Gun Drilling territory JMO. It's deep but not DEEP. Most 3mm Jobber length Drill have 40mm flutes. But if you have a Gun Drill laying around, well shit yeah.

    Really this isn't a tough job, it's just figuring out how to go faster.

    R

    Definitely not gun drilling. Mikron, Guhring, Mitsubishi, and I'm sure others all stock 18XD drills on the shelf. Many of them would probably do this hole in one shot, no peck, given the right machine and TSC. Unfortunately, it doesn't sound like they're a viable option for the OP.

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    Quote Originally Posted by TeachMePlease View Post
    Definitely not gun drilling. Mikron, Guhring, Mitsubishi, and I'm sure others all stock 18XD drills on the shelf. Many of them would probably do this hole in one shot, no peck, given the right machine and TSC. Unfortunately, it doesn't sound like they're a viable option for the OP.
    .
    with just external coolant no way would i not use peck with 50mm depth and 3mm dia twist drill into steel. often see .050" peck depth
    .
    parabolic drills if chips small needs less peck (often no peck) as small chips move along the flutes out the hole. but longer steel chips often just plug up the flutes. and increasing feed and bending and breaking long drill not worth it
    .
    3mm drill is small. they break really easy and are difficult to get out. unless you can afford to scrap parts if drill breaks i would be cautious and not worry about drilling rate. that is if you drill 2 minutes faster but need 2 hours to remake a part you aint saving any time.

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    I brought in gun drilling because of my experiences with it. As a matter of fact you have one operation and the bore is straight and smooth. I did short pieces on a multiple apparatus, four at a time.

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    Quote Originally Posted by Mechanola View Post
    I brought in gun drilling because of my experiences with it. As a matter of fact you have one operation and the bore is straight and smooth. I did short pieces on a multiple apparatus, four at a time.
    The OP is asking about a 3mm hole 50mm deep. As it is, you're saying you would recommend using a Gun Drill? Or you think he should change his set-up to accommodate using a Gun Drill?

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    I suggested that he’d source out. It takes specialised machinery for gun drilling. He can’t do that on his VMC.
    We don’t know how the workpieces look, whether they’re simple cylindrical parts or not. If simple, 60 degrees chamfers would be made on both ends for the bell clamps in the deep drill machine. We don’t know how many pieces, either. Bobbybrown, how many?
    Digger Doug mentioned gun drilling already with post #4.

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    We already have wheels that work pretty well.

    R

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    Update: Pushing in a shorter carbide drill and following it up with the HSS drill worked. Cycle time per hole went from ~3.5min down to around 2min. Thank you guys for the suggestions!
    There are more areas where more high productive solutions are required, will lean on you guys to help me out..

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    Good job!

    Just remember, when you need to get it down to 1 minute, come back. We'll set you up.

    R


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