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Coolants for acetal

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  • MattMaier
    replied
    All the suggestions for tooling are welcome, but I have to do this on a budget, ergo I'll be having to make my own tools, reamers and D-bit drills and such. Also the plastic instrument is a prototype so I can work the method of construction out, then I'll have a go at it in wood.

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  • elf
    replied
    Another option would be to form it using this technique: http://bbs.homeshopmachinist.net/showthread.php?t=43645 This would allow you to easily create different size bores.

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  • Black_Moons
    replied
    Originally posted by bobm4360 View Post
    Compressed air, and withdraw the drill completely every 1/4 inch or so. I've drilled acetal at the same speeds used for aluminum. Experiment with scrap pieces to find what works best for your setup.
    Regards,
    Bob
    I find aluminum speeds wayy too fast, Yes you can drill a little faster at higher RPM but in a deep hole the side rubbing will bite you at higher RPM's with plastics.

    Also, When suggesting a length related to a drill operation, its best to speak in drill diameters and not inches. 1/4" peck distance makes perfect sense for a 1/8" to 1/4" drill bit. Not so much for a 1" drill bit. 1 or 2 diameters deep makes sense for any size drill bit.

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  • Glug
    replied
    Have you considered a drill bit with coolant passages?

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  • Carm
    replied
    Well, another thought since I see problems drilling that long.
    Can you make two sides and chase the hole with a ball end mill or a router core box bit?
    ISTR that acetal doesn't glue well, you'd have to make binding rings, could be a design feature.

    Another possibility is making a clarinet reamer, where one can't afford to have a breakout hole in expensive rare wood. Slow going, but not particularly hard. Sort of a gun drill from the 18th century.

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  • Toolguy
    replied
    Use a parabolic flute drill. Those are made for deep hole drilling. They cause less friction and move the chips efficiently. They do not start well. It's best to start with a spot drill or short drill of the same size for a short bit. Then the parabolic drill will be on location and go fine from there. All the above still applies.

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  • MattMaier
    replied
    Well, it isn't a machine part I'm making for one. It's actually a musical instrument, much like an oboe, of which many low cost oboes for students are made of delrin.

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  • bobm4360
    replied
    Compressed air, and withdraw the drill completely every 1/4 inch or so. I've drilled acetal at the same speeds used for aluminum. Experiment with scrap pieces to find what works best for your setup.
    Regards,
    Bob

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  • peekaboobus
    replied
    Basically you know when you are cutting delrin too hot. It smells like crap. It literally smells like rotten fish. That tells you right away you're cutting it a little hot. Also, those vapors are probably obviously not good for you. So lots of ventilation.

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  • Black_Moons
    replied
    Biggest protip: Let your drill bit cool!

    If your REALLY smart, you'll grind back the flutes that are more then 2 or 3 diameters behind the tip of your drill, Massively reduce side rubbing. Have not done acetal but have done acrylic dry. Needed to use VERY low rpm and let the drill bit cool between several peckings. Once went too fast, VERY ugly hole.

    Keep the drill bit cool to the touch. If its not cool, your hole isent either.

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  • Carm
    replied
    Compressed air, cold gun if you have it.
    Watch out if you have tolerance you need to hit, it is a bit hygroscopic and can have thermal variation; measure at room temp. or at design temp.

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  • peekaboobus
    replied
    I just use water and detergent.

    Melting has never been a problem. It cuts pretty well. Now, if you are cutting acrylic, that you have to watch out for melting. I've never had acetal or delrin melt on me.

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  • MattMaier
    started a topic Coolants for acetal

    Coolants for acetal

    I'm planning a project that will require me to do deep hole drilling in acetal plastic. Owing that acetal is a thermoplastic, I know that if I'm not careful, I can overheat the part and cause it to melt. What is an effective coolant to use on acetal that would be available to a home shop guy like myself?
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