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Good, bad, and ugly - odd tools

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  • Daveb
    replied
    I put a drill bit in the chuck and thought it wasn't cutting very well, when I looked at it, it was a left hand drill, it cut OK when I reversed the drill. I discovered the drill was a standard part, they used to be (maybe still are) used in capstan lathes. I've also had the drills which straighten out rather than drill a hole, I think they're still available but you may have to search for them.

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  • Forestgnome
    replied
    Originally posted by Stu View Post
    Here is an ugly drill bit.



    It came out of a pack of #10 jobbers bits. Does anyone know how drill bits are made?

    Stu
    I have one just like that. I thought is was a reversible bit.

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  • sch
    replied
    Heard a presentation by an Iscar rep 7-8 yrs ago, he said that industrial milling bits/drills with lube-coolant holes down the flutes were made by cutting the flutes and holes straight then
    twisting the bit into a helix before hardening and finish grinding. Don't see any other way to make a hole down a spiral flute for coolant injection.

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  • huntinguy
    replied
    Non clearanced twist drills for wood are not unheard of. Not so common now though.

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  • J Tiers
    replied
    Many wood cutting tools are easily sharpened with a file, clearly not very hard. Some obviously are not for metal, others less obviously. An auger bit is pretty obvious, but twist drills, not so much.

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  • PStechPaul
    replied
    It's a relic of the "mirror universe", where time goes backwards and the CCW rotation of that tool (which is made of anti-matter) fills the hole with chips. It's an "undrill", or "llird" to our Doppelg┘ćngers.

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  • Black_Moons
    replied
    Originally posted by Stu View Post
    Here is an ugly drill bit.

    It came out of a pack of #10 jobbers bits. Does anyone know how drill bits are made?

    Stu
    Clearly that is a bidirectional handed drill bit. It feeds the chips towards the center of the hole for better jamming and binding action. :P

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  • PStechPaul
    replied
    The drill bits I showed seem to have been milled or ground in discrete steps to make the flutes, and then the diameter ground to size. The steel is very soft, and looks "grainy". I can scratch it with a screwdriver but not a paper clip.

    Looking closely at the shank of the 1/4" bit I can see "Made in Japan". These were from the late 50s or early 60s, when that meant something much different from what it does now. I seem to remember some of them being sharpened backwards, but not with backwards flutes. I think I did manage to "untwist" one or two when they jammed.

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  • RichR
    replied
    I thought those might be some kind of new fangled ambidextrous drill bits.

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  • MrFluffy
    replied
    Thats snagged at some point and wound the opposite way. Heres one I did personally using cheap drills in the mill...

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  • Stu
    replied
    Here is an ugly drill bit.



    It came out of a pack of #10 jobbers bits. Does anyone know how drill bits are made?

    Stu

    Leave a comment:


  • J Tiers
    replied
    Shanks are usually pretty close to "correct" or "marked" size, so no idea on that one.....

    The drills without the flute relief are generally older, and/or maybe not intended for metal. The cutaway trailing part of the lands lessens the drag in the hole. Might be other reasons also.

    As far as calipers, don't bother trying to read them to tenths. With a caliper that has a full turn per 0.1", you can usually trust it to a couple thou. The ones with 0.2" per turn, more likely 4 or 5 thou, mostly due to reading errors and zeroing errors, added to tilting of the jaws because this is a contact measurement, and there is a tilting force applied when they touch the part.

    Then also, the pointer is thick and the graduations are rather fine in comparison. It's as much a "resolution" problem as it is a real "accuracy" issue. The basic accuracy of the device as-made probably takes that into account

    We've had folks here claim better accuracy by reading the dial with a magnifying glass and interpolating. You DO get better resolution that way. But not better "accuracy".

    There is no guarantee whatsoever that the basic mechanism justifies the resolution. Most likely it does not. The accuracy may be much less, so you can read to a tenth or two, but the pointer position may be "out" by 10x that much relative to the true dimension of the part.

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  • PStechPaul
    replied
    It reads 0.2335" or 5.93 mm on my HF digital caliper. 15/64" is 0.2344. 6mm is 0.236". So it would be undersize for either.

    However, I used my old Starrett micrometer and it reads 0.2358", as does my dial caliper. I estimate the fourth digit.

    I'm surprised that the digital caliper reads that far off, and I have checked it previously. But I just now checked a piece of round tubing, and the micrometer reads 0.3767 while the caliper reads 0.3745. And I checked a sprocket that read 0.870" in the micrometer but 0.8675" on the caliper.

    So, it seems to be a "Me Trick" tool!

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  • Mike Nash
    replied
    Originally posted by spinningwheels View Post
    sorry English
    Nice play on words.

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  • spinningwheels
    replied
    OK its metric, sorry English is not my first language

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