straightening threaded rods

  • Anyone have any experience straightening threaded rods? I replaced my (rather straight) original 2mm x 4start ender5 rod with 2mm x 1start aliexpress rod that on "glass test" looked just a slightly bent but when mounted and rotating I see that bend is far from "slight" .. I did order few more so maybe one arrives straight but the way they are packing them I assume they get bent in transport 😞 so there's a realistic change the other one will arrive bent too.

    I assume the process would be

    • test on glass
    • bend manually in oposite direction
    • test on glass
    • bend manually
    • throw in garbage, get a next one and try from scratch

    but maybe someone can give me an idea how to straighten it properly 🙂

    in theory, I can have access to a mini lathe, if that helps

  • I did it once with ballscrews, but it is a pain in the ass and it takes a while before you get how much you must bend the screw in what arc to get a bump out. Recipe: A couple of V-blocks, a surface plate and a dial indicator+stand to measure where the bends are. And a (drill)press or the crossslide of your minilathe to push the bend out.

    You really must bend the steel until it leaves the elastic region and enters the plastic region so that it actually deforms instead of springing back. Scary first time; the screw is then bent in a complete banana shape.

  • Moderator

    This is the best video (of an admittedly small number) I've seen on straightening rods/leadscrews. But not sure I'd ever have his patience!


  • @droftarts said in straightening threaded rods:

    This is the best video

    looks interesting ... yes, patience is important here ... I'm waiting on the other rods I ordered (I think in total 6) to see if any of them will arrive straight before I go into straightening .. I can always return to original one from E5 that is totally straight

  • V blocks a dial indicator and the final two ingredients to do it properly (and quickly) are a concentrated heat source and a method of quenching the hot steel fast (a wet cloth) find the high spots with the dial indicator heat and quench until its straight actually quite simple you can get a shift quite straight using this method. I have successfully straightened marine propshafts and turbocharger shafts then balanced them using a schenck optical balancer.

  • @CaLviNx I have vblocks, I have small induction heater ring, small butane torch, I have many rags and water... so the tools are available, but I'm not sure about the process?! I find the high spot, then what? on the video he manually pres it down to bend to other direction / straighten, what's with heat?

  • @smece

    Don't take this the wrong way but if you don't understand the simple thermodynamic process of employing heat (expansion) and applying cooling (contraction) to straighten a steel shaft then you shouldn't really be doing it.

  • youtube is generally quite informative, however my first thought was wouldn't local heat treating the screw lead to uneven wear due to different hardness/tempres?

  • @CaLviNx said in straightening threaded rods:

    if you don't understand the simple thermodynamic process of employing

    hm I understood the idea is to heat the region to make it easier to plastically deform steel and not to employ heat as straightening force .. if I heat the bottom side of the curved shaft it will expand but as soon as it gets cold it will return to the previous position?! how will this permanently straighten the shaft? (not a mechanical engineer, I deal with moving electrons)

  • @smece said in straightening threaded rods:

    idea is to heat the region to make it easier to plastically deform steel

    Hm, my understanding was the differential expansion and cooling will also do the deforming. Stumbled down a YouTube rabbit hole. Interesting stuff, but not sure you can get it done without affecting hardness and temper unevenly.

  • Acme/TR style rods are often rolled from plain C15 carbon steel, and not hardened.

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