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Thread: Recommended RPM for drilling

  1. #1
    Donn McCarthy ABO-AC,NCLEC,CPO OPTIDONN's Avatar
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    Recommended RPM for drilling

    Does any one know the recommended RPM's for drilling poly, hard resin and trivex?

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    Master OptiBoarder
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    RPM? revolutions per minute, I guess?

    I used to drill tons of stuff in house, and I don't think our drill had any way to adjust rpm... I do know that if you push the drill bit through too fast/hard, the lens will crack or at least not make a very clean hole.

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    Depends on what your are drilling, what the drill bit is made of, how sharp the bit is and what lubricants if any are being used.

    Chip

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    Allen Weatherby OptiBoard Gold Supporter
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    Drilling or Milling poly?

    With poly the two areas to watch are the speed and feed rate combined so that you do not melt the poly. Do not just drill poly without pulling the drill bit up every so often to clear the poly chip build up.

    With most of the CNC drills they are actually mills with a milling tool that is smaller than the diameter of the typical hole. The CNC software controls the mill in a circular motion. This method puts less stress and heat build up in the drilling, since you are not really drilling but milling. Milling is shaving the circumference of the whole to make it bigger not just pushing the drill bit through the poly lens.

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    Actually, I thought milling a hole larger was called reaming.

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    The Man, The Myth, The Legend OptiBoard Gold Supporter Fezz's Avatar
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    My understanding of milling is that it is more like digging or shoveling little by little with multiple passes instead of boring thru the material. Others are way more up to the facts though, and hopefully will chime in.

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    Allen Weatherby OptiBoard Gold Supporter
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    Milling vs. Reaming

    Chip said:
    Actually, I thought milling a hole larger was called reaming.
    Below I have posted a picture of a reamer. These small holes in rimless are normally not reamed. They are simply milled to a very exact size by the precision of the CNC milling program. Before CNC you could never approach the accuracy that you can with milling today. That is why reaming was so necessary before CNC. A drilled hole was simply not exact enough.
    -------------------

    Reaming is a process which slightly enlarges a pre-existing hole to a tightly toleranced diameter. A reamer is similar to a mill bit in that it has several cutting edges arranged around a central shaft, as shown below. Because of the delicate nature of the operation and since little material is removed, reaming can be done by hand. Reaming is most accurate for axially symmetric parts produced and reamed on a lathe.





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    Damn, I wish I had some educashment so I would know stuff like this.
    Thanks for the lesson.

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    Allen Weatherby OptiBoard Gold Supporter
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    Knowledge

    Quote Originally Posted by chip anderson View Post
    Damn, I wish I had some educashment so I would know stuff like this.
    Thanks for the lesson.
    This knowledge comes from growing up in a home where my father was a very talented machinist who developed OEM automotive tooling. My grandfather was also a machinist. I learned at an early age that someone has to build the first one of every machine.

  10. #10
    Manuf. Lens Surface Treatments OptiBoard Gold Supporter
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    Blue Jumper Expierience and patience....................

    Quote Originally Posted by Fezz View Post
    My understanding of milling is that it is more like digging or shoveling little by little with multiple passes instead of boring thru the material. Others are way more up to the facts though, and hopefully will chime in.
    I have never worried about fancy words.............but above quote makes sense. I never knew what the speed of the drill was but by going slow, using linseed oil, the diamond drill not overheating we used to drill holes into -15.00 lenses.

    Later in the 60s there were new drills available and these were carbide tipped and you could actually drill galls dry, but again never to long or the drill overheated and the lens cracked.

    Same for plastic of any kind, not too much pressure or the drill overheats, just need a littke expierience and patience
    Chris Ryser
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    http://optochemicals.com............................. http://arcoatings.com

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    ATO Member OptiBoard Bronze Supporter HarryChiling's Avatar
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    I use a dremel that revolves from 5000 - 35000 RPM and the settings on the thing go from 1-10. I use a 6-8 depending on the thickness of the lens and push through slowly. My guess is that since the drill starts at 5000 and goes to 35000 then:

    1 = 5000
    2 = 6666
    3 = 10000
    4 = 13333
    5 = 16666
    6 = 20000
    7 = 23333
    8 = 26666
    9 = 30000
    10 = 35000

    So my guess is that my range is between 20000 and 26666 RPM. Just a guess but probably very close to the actual number.

  12. #12
    Manuf. Lens Surface Treatments OptiBoard Gold Supporter
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    Redhot Jumper Stress factor when drilling...................

    One industry leader said he felt that one of the recurring problems with plastics had nothing to do with the acrylic or polycarbonate, but actually with those who are machining the materials.

    "The biggest drawback in using polycarbonate is the inexperience of the normal machine shop," said Drew. "They are dealing with metals and are not recognizing the pitfalls of the resins. Sensitivity in certain applications is not the same using certain solvents. The coolant might work absolutely fine with one application but cracks another. The reason is because the resin attacks material depending on the stress level. If a resin is used on a simple surface cut, the result is a perfect look. If the same resin is used while drilling a piece of plastic and the part cracks they may wonder why. Well, there is more stress built up drilling a piece of plastic than surface cutting. The plastic is going to react differently, which sometimes might not be apparent. The stress riser is the result of not understanding that material in reference to machining. This is very true with all the thermoplastics."

    See story at http://www.plasticsmachining.com/mag...1/acrylic.html
    Chris Ryser
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    DLO. NA.IC.I.T.PO

    http://optochemicals.com............................. http://arcoatings.com

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