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  #1  
Old 02-17-2013, 06:02 PM
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How to straighten coiled tubing

Anyone have a trick they like for straightening out coiled tube? I bought 3/8 steel tube for fuel lines and it came rolled up in about a15" diameter coil. I walked it out into the garage floor and tweaked it by hand, but that only got it so straight. I tried rolling it between a board and a concrete floor but that didn't do much. Any other ideas?

*EDIT* See post #10 for my home brew solution.
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Last edited by TheBandit; 02-20-2013 at 11:58 AM.
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Old 02-17-2013, 06:39 PM
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Red face

If your looking for getting it completely flat .

I have never had a need to get it that straight

perhaps with two people one to unroll the tube and one to hold it completely flat
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Old 02-17-2013, 07:08 PM
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I'm thinking I may need to whip up a straightening tool to get it straight how I want it. Maybe something like this

www.thecrawlpit.com/download/file.php?id=13494
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Old 02-17-2013, 07:38 PM
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Quote:
Originally Posted by TheBandit View Post
I'm thinking I may need to whip up a straightening tool to get it straight how I want it. Maybe something like this

www.thecrawlpit.com/download/file.php?id=13494
That is exactly how you straighten wire or tube the more rollers the better on the Fourslide there were I think 8 rollers, each set progressed.

E
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Old 02-17-2013, 07:52 PM
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The guy that does my exhaust uses a piece of tig wire to find his bends, when he is done he rolls it out on the floor with a 2x4. I would think the same trick would work for this.

If not that there is always this.
http://www.youtube.com/watch?v=6U0Nrmj6Vkk
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Old 02-17-2013, 10:50 PM
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MasterFabr on this site:

http://www.dtsfab.com/index/index.php?action=forum

Has talked of holding one end solid and spinning the other end in a drill. This somehow makes it go straight.

Ask him there he can explain exactly how to do it. He used to talk of doing it to brake lines and said it worked on other.
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Old 02-17-2013, 10:52 PM
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you need something like this particularly if you are only going to make one part
http://www.durantco.com/wire-straighteners.php
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Old 02-17-2013, 10:52 PM
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Quote:
Originally Posted by TheBandit View Post
This is what I am planning to make the next time I do a complete fuel or brake system. The coiled tubing is much cheaper and longer then the straight lengths that you can buy.

I saw a very similar one that worked really well that had twice as many rollers, 4 top and 5 bottom rollers. Then it was adjusted tighter on the "in" side and looser on the "out" side. Start your tube and just pull it through the machine, out comes straight tube.

Jaysin
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Old 02-18-2013, 02:01 AM
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I buy strait peices ,3/8 is about 20 bucks for 20 foot length
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Old 02-18-2013, 02:20 AM
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It is done! Vise jaw tube straightener







I bought 3 pairs of sliding door rollers from the hardware store and some grade 8 1/4" bolts. They had metal rollers, but all of them are sized for maybe 1/4" track, so they don't fit 3/8" OD tube very well. I figured the plastic rollers would flare out some and they did. I bolted the rollers on 2.75" spacing to a foot long piece of angle iron (1" as it so happens). Then I attached that in place of my vise jaws. It worked great!

At first I wasn't sure if it was going to do much. My first pulls back and forth hardly changed the tube. The key seemed to be putting enough pressure on the rollers to yield the tube. It's not easy to pull the tube through when there's enough pressure, but it can be done and it worked great once I tightened the vise enough. I think I'll head back and buy some more rollers - I can see where that would really help. I drilled the angle for 3 more, for a total of 9 (4 one one side, 5 on the other) if I fill it out.
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Old 02-18-2013, 12:12 PM
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I like that.
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  #12  
Old 02-18-2013, 12:28 PM
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Nicely done Bandit.

Jaysin
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Old 02-18-2013, 03:40 PM
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Nice work. Simple and cheap, but effective.
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Old 02-18-2013, 04:21 PM
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Do you have a shot of the tube as it went in and after?
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Old 02-18-2013, 04:29 PM
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Quote:
Originally Posted by David D View Post
The guy that does my exhaust uses a piece of tig wire to find his bends, when he is done he rolls it out on the floor with a 2x4. I would think the same trick would work for this.

If not that there is always this.
http://www.youtube.com/watch?v=6U0Nrmj6Vkk
Did you catch it when he was done that he showed the tube from the back side and not the main curvature direction? I thought that was funny.
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Old 02-18-2013, 05:49 PM
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Bandit, How long do you think those plastic rollers will last? Do you have to roll it back and forth like that video or can you pull it through once and be done?

Jaysin
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Old 02-18-2013, 05:52 PM
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Quote:
Originally Posted by 2Xtreme View Post
Do you have a shot of the tube as it went in and after?
Sorry I didn't take photos of the tube before & after, mostly because I am ashamed of the state of my work space and it takes a wide shot to show the whole thing. Next time I roll out a length of tube I'll take it to the driveway (or even better, clean shop!) and snap a shot before & after .
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Old 02-18-2013, 06:17 PM
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Quote:
Originally Posted by JaysinSpaceman View Post
Bandit, How long do you think those plastic rollers will last? Do you have to roll it back and forth like that video or can you pull it through once and be done?
Thinking out loud here. Assuming my ancient calculation for tube bending here is approximately accurate, 3/8 x 0.035 mild steel tube with a 36,000psi yield should take less than 145in-lb to bend. With 2.75in spacing, each middle roller could see about 50lb of force. That's probably about double what they'd see under a sliding glass door, but still not a lot for this size bearing. I imagine if they are held straight (double shear would be best!) they would last damn near forever, although I'm not sure on stainless. Mine are probably misaligned a bit due to deflection in the angle and just general misalignment so they may not last as long as they could. I do wish they fit the tube a little better (easily fixed in a lathe). They were $7 a pair at the hardware store - I'm sure you could find something online that would work.

As far as going back & forth, I think if I had a feel for the pressure, I could have straightened out one plane in one pass. I did go back and forth with it and added pressure in stages, but the shape of the tube didn't change much until I got over a threshold (yield). Once over the threshold it, it looked very straight in one pull, but I did run it back and forth and rotated in a couple times. It's hard not to impart some curvature based on the direction I pulled from - all technique that would come with a couple uses. It did take a formidable amount of force to pull it through. Wider roller separation might reduce that some.
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Old 02-19-2013, 10:17 AM
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What you built is pretty close to what we used to straighten large coiled wire. You're on the right track. I've bought steel rollers with ball bearings, either from Reid Supply or McMaster-Carr.
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Old 02-20-2013, 10:32 AM
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Here is a picture of what classic Tube sells to straighten there coils, when you buy in bulk from them. the bottom mounts in a vise on the little tang and you can adjust tension on the upper rollers.


http://www.inlinetube.com/images/str...pict/TLF06.jpg



Carl
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