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IndustryArena Forum > Laser Engraving and Cutting Machines > Laser Engraving / Cutting Machine General Topics > Is it possible to create a sheet metal thread form on a CNC laser?
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  1. #1
    Join Date
    Feb 2010
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    10

    Is it possible to create a sheet metal thread form on a CNC laser?

    Hi,

    Not sure if this is a good place to ask, but wasn't really sure where else my question would fit. We are currently punching a "threadform" (that is what we call it anyways) on one of our CNC Punch machines, I've attached a picture to show what it looks like in case our terminology is wrong.

    So we are replacing one of our Punches with a Laser cutting machine, we currently already have one, and when we need a threadform we just make a round hole with a slight cut on one side to engage the threads. This sort of works, sometimes, but has lots of issues, usually the thread forms the wrong way.

    So my question is, has this been done before, is there a design that can be cut into flat sheet metal with a laser that will then form properly to secure a screw?
    Attached Thumbnails Attached Thumbnails threadform.jpg  

  2. #2
    Join Date
    May 2004
    Posts
    4519
    Without the dimpling effect of the punch, I doubt you can be consistant.

  3. #3
    Join Date
    Feb 2010
    Posts
    10
    Not what I wanted to hear =/

    So in a sheet metal shop that only has a laser machine, what are people doing to make a hole that a screw can be screwed into? (When you can't get a nut behind the material)

  4. #4
    I think you could likely cut a 2D profile with the laser to achieve the same effect. It won't be same, but it'll probably work as long as the sheet isn't too thick. Some trial and error is in order...
    -Sol
    http://www.orangevise.com

  5. #5
    Join Date
    Feb 2010
    Posts
    10
    I'm attaching a picture of what we are already doing, it is essentially the hole we want, with a small slit on the side to help the thread get started. What were you thinking? Some sort of shape? The biggest issue we have is, whatever shape we cut, as soon as you start to screw in you pull the material towards you, but it needs to push away first, maybe it would be a two step process.

    I'm not sure that is practical.

    Edit:
    Forgot to mention, we cut in 24 and 22 guage stainless.
    Attached Thumbnails Attached Thumbnails threadform-2.jpg  

  6. #6
    What pitch is the thread Crazy?

    best wishes

    Dave

  7. #7
    Join Date
    Feb 2010
    Posts
    10
    If I told you it was a 6-32 sheet metal screw, would that tell you what you need to know? If not I will go find out exactly.

    Thanks,
    Dan

  8. #8
    Join Date
    Jul 2004
    Posts
    127
    hmm, I've never heard of a 6-32 sheet metal screw. A standard 6-32 UNC thread isn't meant to be self tapping- it is intended to be screwed into a matching nut/tapped hole that is cut/formed by some means for that size thread. I wouldn't really recommend using a UNF screw in any manner other than that, as the size/shape of the threads was not designed for much leeway in terms of threadform tolerances. A standard sheet metal screw have larger, coarser threads and are designed to be screwed directly into a drilled pilot hole. This may or may not be suitable for your application depending on the load/application.
    If you need to use a 6-32 UNC thread, consider rivot nuts- they are designed for blind holes in sheet metal. They are more options for non-blind applications (clip on nuts, speed nuts, weld nuts, captive nuts, etc)

    Hope this helps,
    -Matt

  9. #9
    That's going to give a 0.79mm pitch (or close to)

    My only concern would be in 24 gauge you won't get near the 60% diameter thread length pull requirement. In a 0.64mm thick sheet (24 gauge) your only looking at just over 1 full thread. If that has to take any kind of pull load it's likely to pull out as a laser doesn't punch any material through, it cuts clean (ish) At least with a pin tip punch hole you will have some deformed material to thread roll into.

    best wishes

    Dave

  10. #10
    Pull up threading *may* work but the cut hole would need to be a little different. Even that way though I'd still have serious doubts as Matt said about integrity of the thread.

    best wishes

    Dave

  11. #11
    Join Date
    May 2004
    Posts
    4519
    I think he meant a #6 sheet metal screw. I do not know what the actual thread pitch is.

    I think if you modify your proposed profile slightly it would increase your luck. See the attached DXF.

    A far out there possibility would be to add a dimpling tool to the Z axis in some way.
    Attached Files Attached Files

  12. #12
    Join Date
    Feb 2010
    Posts
    10
    Sorry,

    I was wrong about the screw, I am now told it's a 6B sheet metal screw. We've been doing this is really high production for about 6 years with our punch, so what we are currently doing is working.

    So if something I say doesn't sound right I'm probably just giving you the wrong information =)

    Dave, can you explain what you mean by "pull up threading"? I'm open to try anything.

  13. #13
    Join Date
    Feb 2010
    Posts
    10
    TX,

    Thanks for the example, we were thinking something along those lines, do you think we would benefit from adding anymore of the "wing"? We were thinking of two originally, something like this.
    Attached Files Attached Files

  14. #14
    Your DXF is a good design for a "pull thread" it relies on the wings being deformed to almost form thread pitches in their own right (One goes up and one goes down). You effectively increase the overall thickness of the material in a localised way much the same as tip punching.

    It's been a long time since I've seen it done commercially (I got out of engineering some years ago) so I'm not sure what equipment is used these days.

    best wishes

    Dave

  15. #15
    Join Date
    May 2004
    Posts
    4519
    I do not see any reason to have a double. The thread on the screw only has one start point. This is another situation of trial and error.

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