Thermal Friction Drilling for Water Bottle Bosses- Mtbr.com
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  1. #1
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    Thermal Friction Drilling for Water Bottle Bosses

    I've been experimenting with thermal friction drilling for my water bottle mounts. I know of at least one other frame manufacturer that is doing this, but I can't remember who it was. If you're unfamiliar with the process, it drills holes by pushing a solid carbide drill bit with no flutes through your work piece at high enough RPM that it melts and reforms the work to create a hole. No material is added or removed, just melted and moved around. The hole can then be tapped with a roll forming tap, which once again, does not remove material. Here's a video http://https://www.youtube.com/watch?v=jk8qjQENViI

    I bought an M5 thermal friction drill, 6mm R8 collet and an M5 x .8 roll forming tap on eBay. I'm into the "hole" setup around $60. I ran it in the mill at about 2600 RPM. Flowdrill has a fancy (and expensive) collet with a built in cooling fan, but I don't think it's necessary if you're only drilling a couple holes at a time. So far, I'm happy with my Chinese tooling.

    I made a few test holes in some .035" wall 4130 and was really pleased with the result. I have not tried on .6 mm wall thickness yet because I didn't have any scraps that thin. I still want to get some .028" wall tube (which is about .7 mm) and try that before I drill a butted down tube, but I'm all in for use on seat tubes or fork blades.

    I devised a highly scientific test procedure to test pull out strength in the laboratory under the back porch. I determined that a single M5 8.8 bolt would suspend my weight (about 215 lbs) without pulling out. Should hold a water bottle on, right?

    I also torqued a fastener much tighter than I would ever take a water bottle bolt and it did not strip. I ran out of time, but later I will round up some torque wrenches and see how tight I can go before thread failure.

    Anyway, I thought it was kind of cool and it saves me time because I don't really like doing the braze on parts.Thermal Friction Drilling for Water Bottle Bosses-outside.jpgThermal Friction Drilling for Water Bottle Bosses-inside.jpgThermal Friction Drilling for Water Bottle Bosses-bit2.jpgThermal Friction Drilling for Water Bottle Bosses-testjig.jpgThermal Friction Drilling for Water Bottle Bosses-hang.jpg

  2. #2
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    Very cool! I think this is a really interesting idea. I'm familiar with both friction drilling and forming taps, but have never seen them applied to bottle bosses.

    I'd be really curious what the long term durability is, as my experience with failed bottle bosses is that they get worked back and forth a lot over time. More of a failure over time than a single event.

    It wouldn't surprise me if these are crazy strong though, and definitely way simpler. No chips, no flux, no brazing, and no relying on cheap braze ons to be made right.

    So just so I'm following, the friction drill you bought actually measures smaller than 5mm, right? so that you can then send in the forming tap into an undersized hole?
    Myth Cycles handbuilt bike frames
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    http://www.mythcycles.com

  3. #3
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    The drill forms a hole that is made to be tapped. The actual bit measures 4.4 to 4.5 mm (it’s not round) and the hole it makes is pretty close to 4.5 mm as well.

  4. #4
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    The hole closet to the end looks to have flattened the tube a bit. I suspect that if you aren’t very careful with pressure you’ll end up with large flattish dimples around each boss especially as you start working with thinner tubing.


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  5. #5
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    You are correct. It did flatten the tube, but I was experimenting with different pressures. I pushed too hard on that one. You kind of get a feel for it after a few holes.
    That end of the tube was also not cut very square and the top was not supported by the vise. It was a short piece of tube clamped perpendicular to the vise jaws. In a properly clamped setup; i.e. tube blocks, I don’t think this distortion would be a problem unless you pushed really hard.

  6. #6
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    Stanton bikes is friction drilling.

    https://www.pinkbike.com/news/inside...facturing.html

  7. #7
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    My composites brain is jealous as hell about this
    Disclaimer: I run Regular Cycles (officialy in 2016, functionally in 2020).

  8. #8
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    I’ve spent a little time inspecting formed threads. Pre-form diameter is very important, enough material to form the thread, but not too much to grab the tool. The root of the thread (major diameter of tapped hole) is nearly always very well formed, however the crest of the thread (minor diameter of tapped hole) is dependent on enough material being pushed up to form it. The very tops of the crests will be missing, and actually consist of little “fish mouths” that are the material from the root of the thread on either side that have been pushed up, so not only will it be a bit big on diameter (compared to a cut thread) it will also have a void within it. So when it comes to speccing a bolt you need to maximise you strengths and weakness’s. The crests (major diameter) of the bolt are far more important than the root (minor diameter) as this is the area you are relying on for maximum contact and load transfer.

    Having said all that, 2 M5 bolts are way overkill for holding a bottle to a frame in terms of loads. As long as you don’t flat spot the tube, I think it’s a brilliant application for forming.

  9. #9
    pvd
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    This is good work!

  10. #10
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    Thanks for taking the time to share. Been watching this process for a while and wondering when I would start seeing it show up.

  11. #11
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    .6 mm wall thickness

    So I went ahead and punched a couple holes in the middle of a 9/6/9 down tube. No denting of the tube occurred and the holes look as good as the ones in the .035” seat tube. I think this process is fine for the thinner wall tubing. At this point, I just need to get the frame put together and see how they hold up over time. Here is a picture. The holes were too much in the middle of the tube to get a good pic of the inside, so just the outside.Thermal Friction Drilling for Water Bottle Bosses-downtubepierce.jpg
    Last edited by jsudar; 07-07-2020 at 10:33 AM. Reason: added pic

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