Super-Blue CNC Part Fixturing

Simple clamps are great if you need to keep the pressure on two parallel surfaces, but if you have an irregular plane, or you need to cut through it, clamps are not the correct tool. The folks at [NYC CNC] feature a video with a clever hack borrowing from other disciplines. Painters tape is applied to the top of a level mounting surface in the machine and then burnished. The same is done to the bottom of the workpiece. Superglue is drizzled between the tape layers and pressed together so now the stock is held firmly below the toolhead.

Some parts are machined in the video, which can be seen below, and the adhesion holds without any trouble. One of the examples they cut would be difficult to hold without damage or stopping the machine. The accepted wisdom is that superglue holds well to a slightly porous surface like tape, but it doesn’t like do as well with smooth surfaces like metal. Removing residue-free tape at the end of a cut is also cleaner and faster than glue any day.

If you have yet to cut your teeth, you can watch our very own Elliot Williams getting introduced to CNC machines or a portable machine even a child can use.

Thank you for the tip, [Keith Olson].

20 thoughts on “Super-Blue CNC Part Fixturing

  1. Now that is indeed a cool trick!

    Workholding for really thin stuff is difficult, vacuum tables with a serious vacuum pump of course work spectacularly well, I’ve used them extensively and they totally work, and it’s not that hard to make a vacuum table, but unless you have creative gasketing, the second you break through the bottom of the part you break your vacuum and your part will fly off the table.

    This method gets rid of that possibility and I have never seen anyone use this before on the job. I have seen some people use double-sided 3M super thin tape but it’s really difficult to get the part off afterward.

    The oldest trick is using what’s called a wax chuck, Jewelers and watch makers use it quite a bit. A finely grooved brass plate surfaced totally flat, and your part is held to it using meltable hard shellac. Superglue straight works well too. I’ve made watchplates for restorations using this method. Denatured alcohol dissolves superglue with a soak.

    Don’t underestimate cyanoacrilate (superglue)

    1. ” I’ve made watchplates for restorations using this method. ”

      Now, this “watchplate” you made, that is different than the grooved brass plate you mentioned earlier?
      -Not A Watch Maker

      1. Yep, as in the mainplate and bridges of a mechanical watch.
        If I knew how to post images to this, I would.

        Im a really weird dude. I got a degree in Japanese, then went into precision machining, and later went to school for watchmaking out west for almost 2 years. I work as a machinist, but trained watchmaker too.

        Someday Ill learn how to build a proper website, and upload pictures of all the neat stuff Ive done and do, but for now, just chillin.

    1. It may be that the difference is that smooth, clean metal provides a good-enough bonding surface (if they’re both perfectly flat, even air or water will mate the two surfaces). If you’re gluing two rough castings together, you’re going to have a bad time.

    2. It does work well metal to metal- but only if very, very flat, very clean (use denatured alcohol, not isopropyl!), and on a so called wax chuck as described above.

      It can work without a wax chuck- but flatness and cleanliness are absolutely paramount. Ultrasonic cleaning if possible helps, just finish in denatured alcohol or Tri chloro ethaline (watchmakers solution called “One Dip”) in the ultrasonic so there is no moisture at all. Putting it around the edge helps too.

      Ive made elaborate clock barrel clicksprings on O-1 flatstock doing exactly that

  2. This was the way I used to use most of the time a year ago until I machined some aluminium clamps.
    I’ve seen it been used on youtube, an old woodworker who learned the technique from a young apprentice. At first he couldn’t believe it would work but has since switched from double sided tape. I guess you’re never too old to learn from the young :)
    I prefer clamping unless I need to machine the whole volume. I used it on wood, aluminium, brass plate and foam. Still, it releases unexpectedly sometimes, making stuff fly around the shop. Once I had a piece of foam release and wrapped itself entirely on the endmill, stopping the 1.5kW spindle. Luckily the VFD was smart enough to cut the power. No damage was done except to the foam. After gluing the foam back together it was still usable.
    Another issue sometimes is that some of the tape facing sticky side up can get caught on the end mill, or leave residue on the end mill making it quite hard to clean the end mill and messing up cuts.

  3. The critical thing in machining like this is chipload- meaning you can’t take as heavy a cut on your material like this. In the video, he could have flycut that item flat in 1 pass if it was in a vice- he did it in 4 passes- to lower chipload and forces on the cutter, also to even out deflection of the material squishing out of the way under the cutter at a very small level, so that it truly faces flat. Even if the tape and glue hold it- if you put an indicator on that sheet, I guarantee you could make that deflect maybe 0.003″ if you pushed on it, hence why he mentioned trying that in the video.

    Nothing in machining is ever completely solid, once you realize everything is in some state of bending under pressure (yes, even carbide bends, just extremely small amounts, precision machining accounts for this), you can machine to much tighter tolerences.

  4. Ok, he’s created his own double-sided tape, which he preps and uses exactly like 3M tape. I guess it’s cheaper.

    Soaking in coolant can help release it. Also, you can give the part a bit of a knock. That can break it free if it’s got enough mass.

  5. I’ve already seen similar process used when I was working in aerospace industry, on Dassault Falcons. Massive structural parts made of aluminium, steel or titanium (like rudder, door or motor mouting ferrules) were simply cemented on a receiving plane. As I was working on structure and not on parts, I don’t know what king of glue were used, but I know that once machined, parts were put into deep freeze, that make the glue crack…

  6. I really hope NYC CNC’s channel can stay up after YouTube’s new rules goes into effect. Sad that so many excellent channels are affected by YouTube’s virtue signaling.

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