# Tube Bending



## ggodwin (Apr 25, 2011)

Hey folks!
This is my first post on your site. I hope you don't mind a BMX builder intrude on your knowledge.
I am looking for a simple way to bend some 4130, 6061 & 7005 tubes to be used for seat and chain stays. Do you have any recommendations? I am very small and need something "in expensive". I just can't afford to pay to have them bent or to buy the ones that are pre bent.

If you have any recommendations I would appreciate it.

Thanks!


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## CBaron (May 7, 2004)

ggodwin said:


> Hey folks!
> This is my first post on your site. I hope you don't mind a BMX builder intrude on your knowledge.
> I am looking for a simple way to bend some 4130, 6061 & 7005 tubes to be used for seat and chain stays. Do you have any recommendations? I am very small and need something "in expensive". I just can't afford to pay to have them bent or to buy the ones that are pre bent.
> 
> ...


Early in our frame building life we bent all of our SS with a conduit bender we bought at Lowe's. It was crude and made identical replications difficult but we make 10-15 bikes this way.

Later,
CJB


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## mattty (Feb 26, 2009)

i use this one with a few modifications to keep the strap part from moving, and to increase its surface area (the stacks of reamed out washers increase the surface area):

http://cgi.ebay.com/NEW-INDUSTRIAL-...ultDomain_0&hash=item20b8c69ab1#ht_809wt_1344

http://www.pinkbike.com/photo/5762364/

I had to weld the bolt in to keep the strap part from slipping outward (it takes a lot of force to bend .049 and thicker)


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## CBaron (May 7, 2004)

We used this and simply duct tape the tube to the bender so that it would "stay" in place. I told you it was crude....


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## offroadcyclist (Feb 22, 2004)

I made a bender like this one that Walt made:

http://waltworks.blogspot.com/2008/12/scrappie-my-new-tube-bender.html

The only thing I did differently was I used curved angle iron as the form instead of wood.

It works great with steel 1/2", 5/8" and 3/4" round tubing, I've never tried to bend aluminum with it though.


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## Blaster1200 (Feb 20, 2004)

I am at the early stage of frame building where I use the conduit bender. I mark the point where it goes into the bender with a Sharpie, and a digital angle finder to determine how much I bend the tube.


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## febikes (Jan 28, 2011)

I don't think it needs to be all that complex especially for seat stays.



I was happy with the result and found that it was not hard to make a uniform bend because I simply made a hash mark on the table so I would know where to pull the stay to. The radius of the plate work great for the stays an a MTB, you might want to use a 35# plate for a BMX bike but that is just a guess. For thicker tubes the extra leverage of a tube bender might be helpful but the seat stays bend fairly easy.


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## einreb (Nov 5, 2010)

febikes said:


> I don't think it needs to be all that complex especially for seat stays.


I like the cut of your jib.

-b


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## Blaster1200 (Feb 20, 2004)

febikes, what stays are those that you're bending?

I love that threaded plate you have! You don't know how much I want one of those!


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## febikes (Jan 28, 2011)

In the photo, I am bending NOVA stays.

The index plate is something I took off an old broke down CNC machine.

Similar stuff can be found at scrap places especially if you go in person.
http://www.hgrinc.com/

A shop can also make you one but it would likely be fairly pricey and expensive to ship. Mine is something like 14"x30" and 1.5" thick of steel. The surface on mine is beat up so I can't use it for precision work but for many projects it is really useful.

At some point I will build something similar to Walt's design...
http://waltworks.blogspot.com/2008/12/scrappie-my-new-tube-bender.html


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## smudge (Jan 12, 2004)

ggodwin said:


> Hey folks!
> This is my first post on your site. I hope you don't mind a BMX builder intrude on your knowledge.
> I am looking for a simple way to bend some 4130, 6061 & 7005 tubes to be used for seat and chain stays. Do you have any recommendations? I am very small and need something "in expensive". I just can't afford to pay to have them bent or to buy the ones that are pre bent.
> 
> ...


how many do you need to bend? How expensive is your time? How accurate and repeatable do you need them to be?

I've built my own dies, used a JD2, used various fork blade benders, gone through the whole cerrobend thing and finally an Anvil bender. The Anvil has been one of the biggest time savers to come into my shop. Now that I've had it for about a year and have records of setups and pin stops, bending a set of matching stays is pretty much a no brainer.

My vote is to suck it up and buy something to do it right the first time.

edit: I don't want to make it sound like the Anvil is the ONLY way to do it right. There are other (more expensive) options out there. But once you factor in time and all the stuff that doesn't produce a good result, the Anvil is the best value IMO.


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## DWF (Jan 12, 2004)

smudge said:


> how many do you need to bend? How expensive is your time? How accurate and repeatable do you need them to be?
> 
> I've built my own dies, used a JD2, used various fork blade benders, gone through the whole cerrobend thing and finally an Anvil bender. The Anvil has been one of the biggest time savers to come into my shop. Now that I've had it for about a year and have records of setups and pin stops, bending a set of matching stays is pretty much a no brainer.
> 
> ...


Thanks, Smudge, I'm glad your digging it. Need to get yours updated to the new alignment arm stuff.


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## Thylacine (Feb 29, 2004)

Hang on.

Set-up fees for mandrel bending is like 60 bucks per bend, and then each bend is about 4-6 bucks.

That's expensive?


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## smudge (Jan 12, 2004)

Thylacine said:


> Hang on.
> 
> Set-up fees for mandrel bending is like 60 bucks per bend, and then each bend is about 4-6 bucks.
> 
> That's expensive?


isn't it? It depends on the production schedule, whether or not you want to carry inventory, frame size differentiation, tube diameter differentiation.

FWIW, I use two different radius dies per stay, different diameters between CS and SS. That's four setups and $240 in setup fees. If you're the builder, how many trips to the bender do you need to make before you slap yourself in the forehead?

I'm going through this again right now with 34.9mm tubing. I could keep sending them out to the bender that ruins 80% of what I send him or I could spend a few hundred $$ paying a local CNC shop to make me dies and blocks and then at least three days of my own time designing and fabricating a hydraulic press. For the expense, risk and time it takes me to send it out, I'm better off doing as much as I can and bringing the operation "in house".


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## smudge (Jan 12, 2004)

DWF said:


> Thanks, Smudge, I'm glad your digging it. Need to get yours updated to the new alignment arm stuff.


It looks like the new dies have a doodad machined into them that mine don't. Looks sweet though, I like your take on it.

I got the 2-bolt SS tube blocks BTW. Thanks!


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## DWF (Jan 12, 2004)

smudge said:


> It looks like the new dies have a doodad machined into them that mine don't. Looks sweet though, I like your take on it.
> 
> I got the 2-bolt SS tube blocks BTW. Thanks!


New mandrels do but we have a retrofit system too. You can either send yours to us and we'll retrofit it or you can do it yourself (two .188 pin locations and d&t for 1/4-20 or M6x1 hole).


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## smudge (Jan 12, 2004)

word. I'll give you a call on Monday. Looks like I need to buy a 0.188 reamer.


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## ggodwin (Apr 25, 2011)

Funny stuff here...
Today I am googling tube benders again and I come across my two year old thread. Since making the original post nothing has changed in terms of my bending. I am still sending them out to a shop and wasting money. I don't do many frames, but with a magazine article coming out and one of my frames 1 of 4 discussed I figure things may pick up.

Some of the posters at Practical Machinist pointed me in the direction of the Di-Acro benders. These are a much more expensive but I have been told that they are well worth the price. I have found a couple on craigslist that I am looking into. Do any of you know much about them? Specifically the ones linked below.

The first one seems to have a lot more components on it. I don't know if all that is needed or not. The one below is much closer to me but I don't know what is missing on it.

Do any of you know much about these?

Diacro 1 Bender

No 1 DIACRO Hand Bender 2" Radius Cap 3 16" Steel Round Bar Cap 24607 | eBay


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## unterhausen (Sep 28, 2008)

#1 is too small, you really want a #2. #3 will work.

The quikloc on the craigslist ad is worth the money, not having it is a pain.


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## ggodwin (Apr 25, 2011)

Will the #1 work for Aluminum tubing? That's pretty much all that I'm making now.


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## ggodwin (Apr 25, 2011)

Let me also add. I'm just bending 1/2" seat and chain stays on small BMX race bikes for 3-6 year olds. 

Crazy I know, but I found a nitch market.


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## TrailMaker (Sep 16, 2007)

Hey;

Think outside your current little box and look for something that will do what you need to now, and more. Having something for one immediate need is not very useful when something more in depth comes along. Versatility pays in the end.


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## unterhausen (Sep 28, 2008)

problem with a diAcro #1 is the diameter of the largest die you can put on it and the leverage you have. I would jump on that #1 for racks or other small stuff if it were near me, but I think you will be pushing it to do 1/2" stays.

A diAcro is what you want, but you have to recognize that it's a pretty big investment. People make their own dies, but there is a pretty big investment required to do that too.


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## ggodwin (Apr 25, 2011)

Well, I made a decision that I am thrilled with. I didn't buy a tube bender. Instead I save major money and made a tube bender out of Oak. Basically, I made something that bends both right and left seat stay and secures it while I make my mitre cut for the seat post.

Here are a couple pictures.


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## ggodwin (Apr 25, 2011)




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## ggodwin (Apr 25, 2011)

The answer before the question. The 2x2 horizontal piece is simply a slide/lock. I insert the tubes and slide the handle up and it pushes the the two outside die's inward toward the two fixes dies. I used a basic 1/2 router and made the rounded groves for the tube to lay in. Inches the are bent I move the entire piece to the whole saw and mitre the tubing.


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## ggodwin (Apr 25, 2011)

FYI it takes me 2 minutes to bend and another 5 minutes to mitre the two tubes. I used to have to drive 60 miles round trip and pay $8 a bend. Then it would take 10 minutes on each Mitre and there was never a guarantee they were the twins.

I'm making another on for the chain stays now.


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## sonic reducer (Apr 12, 2010)

I made my bender dies out of ~1" thick drops from 8" delrin round stock, routered with a 1/4 ball for 1/2 die, 3/8 for 3/4, etc. cut each round in half and through drilled them, tapping one side for 1/4-20 bolts. i will make a 5/8 die soon but the cost will include a 5/16 ball bit i dont have yet. i made the tubes to be a tight fit between the dies, and that the centerline of the tube was past the edge of the die. so closer to a u shaped profile than a half circle. the chassis of the bender is 2 pieces of plate that sandwiches the die and holds the pivot and follower. welded to a square tube for securing to something. the pivots are normal 1/2 bolts. the followers are just some unknown hdpe looking plastic I drilled for the size of the tube then ripped in half.
I have gotten some pretty decent bends out of .75x.035 4130 for my swingarm. NO marring or deformation.
plastic is cheap enough and totally workable with woodworking tools and seems to hold up well enough so far. I would totally recomend plastic if you are trying to make your own dies with a router.


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## alshead (Oct 2, 2007)

ggodwin said:


> FYI it takes me 2 minutes to bend and another 5 minutes to mitre the two tubes. I used to have to drive 60 miles round trip and pay $8 a bend. Then it would take 10 minutes on each Mitre and there was never a guarantee they were the twins.
> 
> I'm making another on for the chain stays now.


ggodwin- can you show this process a little better?


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## ggodwin (Apr 25, 2011)

I can. But please note. This is for small kid frames and the tubes are .035 aluminum and bend easily by hand.


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## backintheday (Aug 20, 2013)

I've been kicking around the idea to try my hand at frame fabrication and am now just soaking up all the info I can. It's obviously very Jig intensive and this has really started to intrigue me. I am almost more excited to fabricate the jigs. I have a wood working background and am used to spending all day making a jig just to progress a project by one cut. Anyway.....

Tube Bending. 

Quality options seem very expensive so I thought I'd make my own. I really like the Anvil approach. I would value any input critiquing their design so perhaps I can address these issues in mine. Or perhaps just a wish list of features/ capabilities.

Also, any insight into why they use odd bending radii? all on the 3/8's? Is it so the inner radii of a 3/4" dia tube is on an even inch? Is that important?

Thanks. I hope to start contributing to this site.


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## PithyBikes (Dec 30, 2014)

Awesome thread. Thanks everyone for sharing. This thread inspired me to make a tube press. Specifically one like offroadcyclist's bender. I don't own a large machining vise so I built a press. Attached are some pics of what I ended up with. I'll post more progress pics in the coming weeks. Also, I shot some video of the build. Cheers.

The press





And a jig I made so I can cut a form.


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## PeopleForScience (May 15, 2012)

Out of curiosity, what brand/model is your band saw? I've been trying to find something that isn't super large but can still cut metal and it looks like you have a pretty good setup there.

Edit: forgot to mention that the tube bending jig you made is rad.


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## PithyBikes (Dec 30, 2014)

The bandsaw is:
Chicago Electric Power Tools Portable Variable Speed Band Saw. It's worked really great for me so far. Cheers!

Amazon:
Chicago Electric Power Tools Portable Variable Speed Band Saw - - Amazon.com

I welded up the frame that holds it upright. And welded a plate for the saw. I got the idea from these images floating around on google

HF Porta Saw Stand Complete 1 Photo by uapkt84 | Photobucket

https://bladesmithsforum.com/uploads/monthly_12_2008/post-20007-1230507133.jpg


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## PithyBikes (Dec 30, 2014)

Hi Folks,
Some more progress. Video here.

But pics attached you're not into videos


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## TrailMaker (Sep 16, 2007)

Hmmm...

My gut would tell me that you'd be far better pushing with the full form than with the segmented blocks, but that is just a hunch.


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## Eric Malcolm (Dec 18, 2011)

Hey, neat video.

I was kind of hoping you were going to insert a piece of alloy in there to demo a bend..

What sizing are you going to bend with it? Steel or Aluminium?

Eric


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## cable_actuated (Jun 7, 2012)

PithyBikes - those videos are amazing! I really enjoyed watching your thought process and implementation. I'm like a cave man in the garage compared to you.


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## PithyBikes (Dec 30, 2014)

Eric, I'll be bending 22.2 ROR chain stays. From Henry James.
I actually already bent them but haven't organized my footage yet.

TrailMaker, your gut is right. I did run into problems. But, actually the problem was more with the wood form.I'll post pics next week when I have time to get pics.

cable_actuated, thanks!! Hahah you don't see all my mistakes though. I cut that stuff out  I'm so glad you enjoyed it. I plan to keep doing the videos till I have a finished bike


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## PithyBikes (Dec 30, 2014)

Hi guys,
I bent the chainstays! ..and messed up one in the process. But I learned a lot 

Video of bending in progress here.

Cheers.


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## ggodwin (Apr 25, 2011)

Nice video! I need to make me a new bender also. Working heavier Aluminum now and need a little more power.


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