Judson Yaggy

Straightening bar stock/silo hoops

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Ok braintrust, here is my dilemma.  I made about 30' of interior barrier railing (95% fabricated) out of some very old, rusted, pitted silo hoops I had in my scrap pile for some clients who wanted the most rustic, salvaged look and materials I could find.  It was around 200 linear feet of 1/2" and 9/16" material.  Silo hoops are both curved to begin with and abused from the deconstruction process, so they needed to be straightened.  Doing so was ok if tedious for that amount of material.  Trouble is, they liked it so much they changed the design of the other railings in the house and want the same material.  

I would love to know any tricks that would make straightening another 700 linear feet of material faster than my process.  What I've been doing is 1. cut to rough length.  2. roughly tweak to approximate straight with bending forks in a vise  3. put flat dies in the fly press and work the high spots down.  See photos below.  Working cold to save time and rust, sorry, I meant patina.  Anyone have a better way?

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Basically, your pics show how I would do it. Bending forks and scrolling wrench. If you arent using stands, then Id add them as needed.

I use my vice instead of a press.

Lol, hire an apprentice.  :)

 

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This is what your sway backed anvil is for! Honestly, use somthing like the vice or scrolling forks to get close and then finish on the anvil 

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You do not need the entire length perfectly straight. Just straighten out most of the curve so the pieces can be stored. Then cut what length you need and finish straightening that one length. Easier to handle that way.

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Hire help; the proverbial highschool kid...

The machinery to straighten stock automatically is generally too expensive for small shop use.

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How straight does it need to be? I used to straighten out the 12 foot long bent bar stock for the CNC screw machines. Anywhere from .0625"-.625" using a small lathe. By flexing past the yield point it as it rotated I could get the bars arrow straight most of the time, or really close on the bigger diameters. The small stuff, up to say  .125" I would extend about two feet out of the collet, grab the bar with my right hand and turn the lathe on  speed varied on alloy, diameter, etc... I would grip the bar in such a way that it made a kink as I slid my hand down the length from the collet out. Once that was straight, I'd pull another two feet out and repeat. With heavier stock I would get the bend pulled out enough where the end wobbles an inch or so, then just push it off center as it rotated. Repeat as necessary.  Once you get the hang of it it went pretty smoothly. With rusty stock you would push with a chunk of plastic, or wood instead of your hand.

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7 hours ago, anvil said:

Basically, your pics show how I would do it.

That's good to know, was pretty sure I was on the right track, just fishing for a trick I hadn't heard of!

7 hours ago, Charles R. Stevens said:

This is what your sway backed anvil is for!

My anvils are dead flat, as they shoud be in a professional architectural shop! (poke poke!) If I want to hammer over a hollow I use the swage block.  

6 hours ago, Glenn said:

You do not need the entire length perfectly straight.

I do need the entire length very straight.  I've cut the rough length to +2" oversize.  The rail sections are between 6 and 10 feet long, and this is for a very precise installation, despite the rough looking material.  Should have said that the bars run horizontally, thus the longer lengths (not 36" balusters).  

 

4 hours ago, BIGGUNDOCTOR said:

I used to straighten out the 12 foot long bent bar stock for the CNC screw machines. Anywhere from .0625"-.625" using a small lathe.

That's interesting!  You win the prize for most helpful.  Will try that tomorrow.  

 

Thanks all!

 

I should add that my apprentice went and got himself a job with lower pay but more regularity off the farm.  Teenagers!

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Forgot to mention that the part extending out the back of the head stock will need to be restrained somehow to keep it from whipping. I had a length of PVC that I used that was supported on a stand. 

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Posted (edited)

 

A set of powered bending rolls is the go to for straightening...even a tire roller will work but the hand cranking will steal your time and energy savings. 

I have also found that a lot of old silo or tank rings are wrought iron.

As to Charle's comment, afraid I have to enthusiastically agree.

Straightening stock on a gently swayed anvil is by far the fastest hand method.

 

Edited by arftist

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16 hours ago, Judson Yaggy said:

I should add that my apprentice went and got himself a job with lower pay but more regularity off the farm.

Lol, I just wanted to let you know that every one of your responses made my day. Id put you to work any day of the week straightening iron,,, on my dead flat anvils.  ;) every one of your responses hit the mark.

 

Back to reality, are those pieces wrought, mild  or high carbon? Ive seen it around but never got any. Im guessing wrought. 

.

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Spark test and bend test the rods (for wrought iron, some can be high quality and not readily show the grainy structure).

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Wrought or Mild depending on when it was built.  And I have always found it easier to straighten on an anvil with a swale rather than dead flat as you generally need to push it a bit too far and have it spring back to straight, rather than push it to dead flat and have it spring a bit off.

Since you are cutting to length+ I'd cut the next one 3/4 the way through and break it off to see if it was wrought or mild. (And if it was built in the great depression they might be a mix; as folks used what they had to hand.)

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On 5/25/2019 at 6:53 PM, Judson Yaggy said:

 The rail sections are between 6 and 10 feet long

Then you need to rough straighten a section of the hoop and cut it just beyond 6 or 10 feet.  You can then take a sorta straight 6 or 10 foot section, which can be a manageable length,  and make it really straight.

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On 5/26/2019 at 11:28 PM, Glenn said:

straighten a section of the hoop and cut it just beyond 6 or 10 feet.

 

On 5/25/2019 at 6:53 PM, Judson Yaggy said:

 I've cut the rough length to +2" oversize.

In regards to the questions regarding wrought iron...

Only one lenght out of 35 so far has been WI.  It had a really nice 4" long scarfed forge weld.  I placed it at eyeball level on the first stair run of this railing, and pointed it out to the clients.  They made appreciative noises (eye roll).  Quite a few of the rusted in place nuts on the tensioning ends show obviously wrought grain, even if they are on mild steel hoops.  

Silo hoops in my experience are interesting.  A very few of them are indeed wrought iron, and a fairly good grade.  The vast majority are mild steel, and are of the antique "even softer than 1020" type.  Those forge like butter without the usual quirks of WI.  But the remaining 3% or so seem to be weirdly red short, prone to fracture at normal working temp.  

 

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Interesting, thanks.

I have a nice bar of reforged wrought given to me by a blacksmith friend. These were made from hoops or strap off an old narrow gage rr water tank. Its very clean wrought. 

Ive seen these hoops at scrap dealers and wondered what they were made of.

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Tension the lengths.  Put a bend in each end and pull it with about 1 ton of force. (have no idea what kind of force it will take ) but this will indeed straighten the bars. 
If you over tension the bars you can pull them apart.  

Stretching the bars will straighten them as will counter rollers but unless you have one handy the stretching thing works very well. 

The other thing that is nice about doing it this way is a little hit with the hammer on the really high spot will center it nearly instantly. 

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Something Jen said triggered my memory. Try slapping the hard on a thick welding table. If they are soft, one good slap should do it.

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Don't they have a threaded end? If so make a pulling yoke you can attach to the trailer hitch. Make a set of straightening rolls by welding solid bars vertically to a piece of plate you can spike to the ground. Slip pipe over the vertical bars to act as rollers. You want them spaced so the bar to be straightened is flexed slightly back and forth as it passes through. 

Now spike the plate to the ground and lace a silo rod through to start, screw the yoke on the end and pull it through with your vehicle. If it's not straight enough flip it over and draw it again. By flip it over I'm referring to it's original orientation as a ring, not end for end. Yes?

If it's still a little wonky take a hammer to it but it should be darned close in a draw or two.

Frosty The Lucky.

 

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