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Thread: Fine Fluteless Taps. Keeping track of suppliers...

  1. #11
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    BTW to help your search, these are called "bottoming taps" in the machinist
    world, I called up some suppliers in LA and they all had them... The sales droids get confused if you say fluteless...

  2. #12
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    Quote Originally Posted by yaddatrance View Post
    BTW to help your search, these are called "bottoming taps" in the machinist
    world, I called up some suppliers in LA and they all had them... The sales droids get confused if you say fluteless...
    Not the same thing. Fluteless is a basic description, seems to include that, but a true fluteless thread-forming tap is designed to make the whole thread without cutting, in a hole drilled to exact size to allow displacement and hardening of displaced material. Bottoming taps might be too brittle, a thread-form tap must be tougher, with smoother finish, and has a taper. They also aren't strictly round, but have a kind of blunted triangular section.

    Nothing to stop us from grinding a taper on a bottom tap though. We're only interested in soft ductile materials, mostly, for mounts, so being very hard will make it tough enough so long as we avoid anything but rotation when applying them.

    I'm still not clear about price though. Some say you can get one for $10 or around 5, others say that those are crap and you won't get a good one for less than 30. I think it's worth trying a cheap one for aluminium, so long as it's lubricated well. I asked a supplier of what looks like a cheap 12 BA but I haven't had an answer, and don't expect one now till after Easter if at all.

  3. #13
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    I looked a little more on the mcmaster website and you can buy thread forming M2 screws with .4mm pitch for about 50 cents a piece. Unless you plan on making a lot of stuff these would probably do what you want for cheap.

  4. #14
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    I can't find anything truely fluteless below 4-40. Only 2 flute units are available. It would be nice to get a little more than 70% thread engagement and have the hardening effect though. I have found one source that stocks taps special oversize for anodising and they have taps down to #0-76. I will continue the search of vendors I can get hold of........
    You are the only one that can make your dreams come true....and the only one that can stop them...A.M. Dietrich

  5. #15
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    Quote Originally Posted by MechEng3 View Post
    I have found one source that stocks taps special oversize for anodising
    And that's a very good point too, but do you mean undersized?

    Pit.
    A little bit werrrr, a little bit weyyyyyy, a little bit arrrrgggghhh

  6. #16
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    Nope, over. Anodising forms a greater thickness, as the oxide layer is not only less dense, but more porous. It is a good point though, I agree. On the other hand, the oxide might make a grinding surface which on threads that small is a possible problem. If I were getting parts anodised, I'd probably stop the threaded holes up somehow first. Even the anodising process itself might be a problem, letting H2SO4 get at threads that fine. Maybe optics mount makers don't have a problem with this, but I think it's easier to keep those threads as clean metal. It's already work-hardened, and the friction will be lower, and the percent of surface engagement will be higher, so the accuracy and repeatability should start good and remain good.

    Those M2 thread-forming screws sound like a good idea. I considered self-tappers but abandoned the idea thinking that most had tapers, flutes, and all kinds of unwanted nonsense. I think it could be difficult to hold them straight enough to start a high quality thread anyway.

  7. #17
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    Quote Originally Posted by The_Doctor View Post
    Nope, over. Anodising forms a greater thickness
    It's not the dumping it into H2SO4 and stuffing in the currents that's the problem, it's the cleaning of the work beforehand.
    If you use caustic soda (as many do) or similar as the cleaning agent, you'll be eating away at all exposed aluminium surfaces, including the thread
    Using undersized taps would compensate for any erosion during that stage, well, to a degree.

    I had a batch of stuff ruined because the guys went for a coffee break and left my aluminium soaking in the cleaning tank for too long. It was like putting an M3 bolt in an M4 hole when they gave it back to me

    Pit.
    A little bit werrrr, a little bit weyyyyyy, a little bit arrrrgggghhh

  8. #18
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    I hope they compensated you for that. Liability ought to cover the worth of the parts, not just a refund of the anodizing costs. Which would hurt them but prevent a recurrence.

    I guess I'd stick to either blocking the fine-threaded holes, or better yet, get stuff anodized without them, and drill and thread them afterwards.

  9. #19
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    Quote Originally Posted by The_Doctor View Post
    I hope they compensated you for that
    Yeah, they did cough up some compensation. Fortunately for them is was a small run and the threaded bits were easy to remake.

    Pit.
    A little bit werrrr, a little bit weyyyyyy, a little bit arrrrgggghhh

  10. #20
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    http://www.colinusher.info/Livesteam/mewdata.html
    Some really good info on thread data. The XLS data in the ZIP files is especially good stuff.

    I found a supply of brass and steel 16BA. That's 133.3TPI! Not sure I'll use that though, I have to have at least SOME load bearing capacity there... Anyway, the idea is that it might be better to just drill holes and buy nuts and bolts rather than tap stuff. I just worked out a design for an optics mount that you could hide inside a little fingertip, if it was hollow. Would be useful for generally mounting 5mm optics.

    If anyone knows of good conversion charts for really small UNC, UNF, ANC, ANF, BA and Metric threads, please post. Also, if you know of a supply of VERY tiny stainless stuff, please post. I know that 12BA stainless exists but I can't find any for sale. I'll take 14BA or even 16BA if I can get it. Brass would be too weak, hard steel could rust and at that size this is BAD, but stainless would rule.

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