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Mental Gymnastics - Visuospatial Mind Required

Mental Gymnastics - Visuospatial Mind Required

(OP)
Hello - I've been thinking about a seemingly simple problem for days with no avail. Even the sheet metal "unfolding" software to create a flat pattern from curved shapes fails because it cannot take into account the manufacturing method (manual metal twister). Yes, I know a flight screw can be created with a cold rolling machine, but I would like to produce it with what I have. If you can come up with a solution backed with evidence you are beyond my MIT grad cognitive abilities. Thank you in advance you to those geniuses out there. Please see image.

RE: Mental Gymnastics - Visuospatial Mind Required

That machine can't do it.

The normal way to produce screw flights is to cut flat semicircles, stretch and twist them over an appropriate size tube, then butt weld them.

Mike Halloran
Pembroke Pines, FL, USA

RE: Mental Gymnastics - Visuospatial Mind Required

Just twist it as tight as you can and drill a hole down the center
Kinda like you make a Mobius strip

RE: Mental Gymnastics - Visuospatial Mind Required

You may be able to do it, however, you may have to heat the metal red so as to be able to stretch and you may have to increase the tension as you get more twist. Then as Buggar stated drill a hole thru the center. Experiment MIT graduate.

RE: Mental Gymnastics - Visuospatial Mind Required

One more thing as I tried your method on a strip of paper is to slightly curve the metal strip before twisting it, that way it will follow the twisting motion better.

RE: Mental Gymnastics - Visuospatial Mind Required

I did not mean to plagiarize Compositepro's posting “This is how a skilled craftsman does it:”
Just had the same thought after finding same vid with google

RE: Mental Gymnastics - Visuospatial Mind Required

Depending on how many you need to make, diameter (ID and OD) and thickness of the desired (minimum thick AND maximum thickness) screw "blade" (thickness of the twisted flat bar), and needed stiffness of the assembly and drill thread pitch, I'd stack up the number of fender washers needed to make the number of turns (one washer for each turn PLUS the needed extra length to the length to accomodate the screw thread advance per turn.)
Cut the stack of washers down one side.
Pull each washer apart axially as if you were going to make an old-fashioned spring lock washer.
put the axial rod down the center of the stack, weld the bottom stretched washer in place.
Weld each subsequent washer to the previous set at the butt-weld joint and to the center rod, rotating each to touch the exit of the previous.

RE: Mental Gymnastics - Visuospatial Mind Required

Ditto what Greg said.

RE: Mental Gymnastics - Visuospatial Mind Required

DistressedNerd, you need a tube finning machine: http://www.tulsafintube.com/fin-tube-finning/

Possibly, you might contract out the work.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

RE: Mental Gymnastics - Visuospatial Mind Required

Splitting twisting, and welding washers can work, as shown and discussed already.

If you are dealing with expensive materials, you may throw away less waste by cutting semicircles or other partial circles from sheet, twisting and welding, etc.

There is also the option of cutting the entire helix from solid billet, easily accomplished in a lathe with threading capability, and perhaps a bit faster if you can fit a milling head to the cross slide.

You were possibly thinking of tooling similar to that for making spiral welded pipe, where a continuous strip is fed, tangential to the finished pipe and oblique to its axis. ... but to do something like that by feeding the strip fed obliquely but normal to the axis of the finished article, you also have to stretch the strip edge that will become the outer edge of the helix, and/or shrink the strip edge that will become the inner edge of the helix. That becomes more difficult as the central bore or core gets smaller relative to the major diameter.



Mike Halloran
Pembroke Pines, FL, USA

RE: Mental Gymnastics - Visuospatial Mind Required


SnTMan - That's an hour of time I'm not getting back. Thanks Youtube tube-finning rabbit hole. Amazing the number of countries vying for the tube-finning machine market.

RE: Mental Gymnastics - Visuospatial Mind Required

3DDave, you read my posts at your own risk :)

I am embarrassed I didn't think of that sooner since I once worked in a shop that did that...

On edit: If a person had an engine lathe, some cam followers and some other miscellaneous stuff, and time to mess with it you could most likely make your own setup. Not saying easily...

RE: Mental Gymnastics - Visuospatial Mind Required

Why is OP always distressed? The welded semicircle method is how I've seen bulk conveying screws made.
If the material to be conveyed is not abrasive, I've seen conveying screws for bottles machined from I think it was an air entrained thermoplastic, or maybe FRP. Something cheaper and easier to machine than metal.

RE: Mental Gymnastics - Visuospatial Mind Required

Dunno, maybe because he never comes back to read these threads?

RE: Mental Gymnastics - Visuospatial Mind Required

Hit and run.

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