pipe bending help 3

[jimm007]

Hi i have recentley purchased a 16 ton hydraulic pipe bender for use in my garage, i was hoping to manafacture a roll cage for my landrover. The kit seems simple enough, a bottle jack in a frame with a selection of dies and a pair of adjustable top rollers, the problem is there is no instructions with the kit and when i try to bend steel tube in kinks at the point where the top rollers make contact with the tube, i'm not sure if you are suppose to start with the rollers at the bottom holes and work up to the top or vice versa, can anyone help me,Im avionics by trade so a bit dull when it comes to mechanicle, also it says it does 180 degrees (3 x 60 degrees) not sure how to do that, i only actualy need to go to 90 degrees,cheers jimm

 

[ssn596]

Hmmm you say it is a pipe bender. Uhhh is this some Harbor Freight thing? You also say you are using tubing. Tubing will not bend in this type of rig especially to a 90. What size tubing? Youre using tubing on a roll bar? Think I would want more beef than that, but I won't be riding so its OK with me.

From experience bending conduit both rigid (pipe) and EMT tubing, you need a better bending rig if going to a 90. You also cannot go less than 5 times the pipe radius.

IF it is exhaust tubing then a muffler shop can bend it. They will NOT generally attempt pipe or rigid conduit.

you may try packing the tube full of sand TIGHT and drive wood plugs in ends to prevent wall collapse. Sometimes it works sometimes not. There is a material called low melt melts at around 100 F. If you pour that in the tube you can do real tight bends then melt it out. But it is not cheap.

IF you are doing water pipe ie sched 40 then an electrical shop with a power bender may be willing to bend it for a fee of course ASSUMING you can tolerate the wide sweep.

Dan Bentler

 

[jimm007]

Thanx for your reply the type of machine can be seen at

http://www.machinemart.co.uk/shop/product/details/chv12-12-ton-hydraulic-pipe-bender

I am bending 2 inch od pipe thats 3.3mm wall thickness, its what is used for this type of job...jimm

 

[btrueblood]

Yes, I've played with one of these before. Start with the rollers in the lowest (most interior) set of holes and bend until the tube just starts to kink. Reset the rollers to the next outer pair of holes, and bend some more, etc. until you have your desired angle of bend.

This type of bender will always "kink" or locally buckle and flatten the tube wall. A better bending rig has "shoes" or saddle blocks, i.e. blocks about 1 tube diameter long with a semi-circular groove in it that matches the tube o.d. These are held by pins in place of the rollers, to help support the tube wall during bending and reduce distortion/buckling. Go visit a local auto muffler shop, and ask to take a look at their tube bender in operation. You might want to try and get a local machine shop to make a pair of saddle blocks to replace the rollers with.

 

[btrueblood]

Oh, and to bend past 60 degrees (or whatever the center shoe allows) you need to reposition the part to a new center point, and start bending again from there. Obviously, you will need to experiment a bit to find out how far apart to space the bend centers to get a fairly smooth bend (the word "smooth" here is used loosely).

 

[jimm007]

Thanx for your input btrueblood will talk to my local engineering company, do you happen to know the min bend radius of steel tube ( blueband in england) to bs 1387 spec...jimm

 

[mikek10]

It depends on the method you are using.

If you are rotary draw bending and using a mandrel and wiper die you can achieve a far tighter radius than compression bending

Anything less than 4.5D you will need a mandrel

1D needs a 2 ball mandrel and a wiper die

 

[skinnyj]

We use these types of benders everyday. We don't have this particular brand, but they are the same type of benders.

1. You will always have a small kink at the apex of the bend with this type of bender, but you can minimize it with a few techniques.

2. That bender should bend 90 degrees in one shot.

3. You should never have to move the rollers once a bend is started.

Place the rollers according to the size of the pipe you are bending. For example, if you are bending 2" pipe and the bender range is 1/2"-2" then the rollers would be set all the way out. Grease the rollers and the bender die. If you are still getting kinks where the rollers are located, you may want to polish or custom fit the rollers. If the pipe is kinking in the center, then make a strap to secure it to the bender die so it doesn't move away from the die as you are bending. good luck.

 

[DAVIDSTECKER]

I have not tried this, but I've been told that filling the tubing tightly with sand will reduce the kinking of the wall

 

[mikek10]

Well yes - its effectively acting as a mandrel - but you are never going to achieve results as good as a rotary draw bender with a compression bender