Bending a Stainless Steel Threaded Rod

[Benno85 (Ben)]

Is anyone able to do this? I've called just about every engineering shop in my local area, and the majority can't do it without damaging the thread, except for one place but considering the rod cost me $8 and it will cost $110 to bend, I'm looking further afield.

Any assistance would be appreciated


Benno.

[asimov (John)]

What kind of bend, Benno? Are you looking for a shallow curve, or 90 degree bends...?

Putting a gentle curve in a threaded rod is easy enough - I've done it in an old sheet metal roller. Normally the roller will have grooves in them to accept different guage rod/round bar. When precautions are taken, it won't damage the thread.

[Benno85 (Ben)]

John, it needs to bent to a 7" radius curve. I've got a 3ft length but will only require about 8" of it for a barn door mount.


As you can tell I've not much clue when it comes to this sort of stuff, let alont access to the right tools to even have a go at it

[mental4astro (Alexander)]

There is one cheap way. What you need is a really heavy wooden platform and two long stout nails hammered in so that they won't move, even when you stand on them, spaced about 3.5 to 4" apart, and some old cloth.

Wrap the nails with plenty of cloth to protect the thread

You place the threaded rod between the nails, and pull it so that it gets wedged between the two nails, and slowly put the bend in it, moving the threaded rod to adjust for the radius that is needed.

Do it slowly. It may also help to draw a template to the radius you need to check on your progress.

[mswhin63 (Malcolm)]

You could go for nylon threaded rod instead of metal, if you loading is not that much. easy to bend without damaging.

Application of heat is the only other way but may get uneven bends.

[Benno85 (Ben)]

Cheers Alex, something like an old railway sleeper perhaps??

I've heard that stainless steel is prone to cracking whilst trying to bend it, and that some heat may reduce the risk. Might have to scrounge around a mate's place and see what he's got laying around to help out, as I'll be buggered if I'm gonig to pay $110 if I can do it myself

[mental4astro (Alexander)]

Sleeper, oh yeah!

Try first without the heat. Stainless is a tricky bugger, and doing it slowly helps.

If it does fail, it's only another $8, and you are still $102 infront.

[snowyskiesau]

Brass rod would do the job and is easier to bend.

[mental4astro (Alexander)]

Brass is much easier! No heat either, but still do it slowly.

[Benno85 (Ben)]

I have looked at the brass option (the plans for the barn door I'm building actually call for brass) but I can't get it for under approx. $45 and from only one website in Australia. I can get it from the US for slightly cheaper but the company is out of stock and not sure of when it will be available

[bmitchell82 (Brendan)]

If it was me i would be ditching the SS rod as it is really crud to bend and going for some mild steel thread and say a bright zinc finish something to that degree. Far easier to bend, and will accept heat readily enough.

[snowyskiesau]

What diameter/length is the rod?
Also what pitch thread?

[Benno85 (Ben)]

It's a 10-32 UNF rod, I've got it as a 3ft length but will only require approx. 8" of it.

Specs are halfway down this page.

[leon]

Ben I have done a number of these curved rod drives of various radius, trust me brass is best and very easy to bend yourself.

Leon

[snowyskiesau]

Originally Posted by Benno85

It's a 10-32 UNF rod, I've got it as a 3ft length but will only require approx. 8" of it.

Specs are halfway down this page.

The same supplier you mentioned has brass 10-32 rod for $35 (but I'm guessing you knew that ).
I don't know how critical the thread pitch is but you can get M5 brass rod from here for about $24.
As bmitchell82 pointed out, mild steel, zinc finish rod would be easier to bend.

[bmitchell82 (Brendan)]

I guess what we are trying to say Ben is that do it once do it right have no hassles. try to cut corners the bench is likely to fall on your foot!

[Rod]

Hi Benno,

I have never made a barn door mount but a member of my local club has built a version that does not require a threaed rod. Description is here:

http://www.mpas.asn.au/Astro/Tips/di.../dingaling.htm

Rod.

[Benno85 (Ben)]

Thanks fellas , I now physically have the rod in my possession, and it's much thinner than I thought (less then 5mm and 304 stainless). A quick attempt at bending it and it looks like it could be doable.....as Alex mentioned if it fails then I've only lost $8


Stay tuned, I'll report back over the weekend as to how it all goes!!


Cheers,

Ben

[bojan]

This spreadsheet calculates the rotation rate based on bending radius, rod pitch, gear teeth numbers...
To have the 1 rotation per minute of the bigger gear for your mechanical design, you actually need 7.145" bending radius... Not that this is too important in case of uP driver.
The motor (driving smaller gear, 16 teeth) will have to rotate at 4 rot/minute.

EDIT:
excel spreadsheet updated for reverse calculation (from motor speed to rod bending radius)

[Benno85 (Ben)]

Thanks buddy, I've got my father printing off a template at that size, I'll see how close I can it the exact radius by hand