Thread: bending Gal. pipe - how to

Um, a pipe bender.

DD

Originally Posted by Dingo Dog

Um, a pipe bender.

DD

The pipe bender tends to kink the smaller diam. pipes . I have one and its pain of a thing .

Originally Posted by morrisman

The pipe bender tends to kink the smaller diam. pipes . I have one and its pain of a thing .

That is caused by at least two things.... A mandrel that does not support the sides of the pipe very well, and/or using thin pipe... In my experience with convention benders usually anything thinner then blue band (medium) is generally prone to kinking...

I think the best way to proceed would be to find a pipe bending place, get them to bend up a heap of bends, to which you weld the straight sections...

Bending pipe and ending up with the right dimensions can be difficult and create a lot of scrap.. As when you make a bend the pipe grows, and how much it grows depends on a lot of variables...

Originally Posted by morrisman

The pipe bender tends to kink the smaller diam. pipes . I have one and its pain of a thing .

Would filling the pipe with dry sand prior to bending help?

Originally Posted by morrisman

The pipe bender tends to kink the smaller diam. pipes . I have one and its pain of a thing .

I used to bend a lot of pipe by hand in that bender, arms like bowling pins, make sure to give the other arm a turn. Used to make a lot of side rails and other types of bar work.
The way I used to measure for a 90 degree bend, was to measure overall distance required, find the centre measurement of the pipe, halve the distance minus the pipe diameter and that mark is the centre of the die.
The problem lies in the dies being made for pipe in imperial sizes. The way I got around it was to make a shim half the difference between the pipe and the die. For example 23.3 - 20 = 3.2 /2 = 1.6., 3/4 pipe OD 20 mm, pipe die 23.2 mm. use a piece of 1.6 thick steel sheet approx 50 mm wide and the length of dies outside radius. Insert between the pipe and die, pump away, it may take several pipes on the die spacer to get it right. If you have an oxy set, heating the spacer helps too. Have found that warming/annealing black pipe, till the outside COATING turns white helps also.
The correct size dies can be purchased from places like H&F, for pipe dies to fit the BULLDOZER, a bar/pipe bending machine made in NZ, pretty sure their dies are for metric pipes, I had one about 12 years ago.

Order Code: P508
BZ-P20 - Round Pipe Former
20mm
Suits Bulldozer

ex GST
inc GST

$79.00
$86.90

Hope this is of some help, to those that suffer the same problem. They have other sizes available also.

Kryn

ok SOME GOOD IDEAS THERE.

Seems that having the correct mandrel is the secret to achieving good quality bends

Thanks

The correct mandrels are absolutely essential. You can hire hydraulic benders from some of the hire places, similar to this one which handle pipe from 12 to 50mm. I also strongly agree with the notion of making bends and then doing a cut and weld to form accurate frames. However you can determine bend gain empirically by cutting a sample of pipe that is big enough to bend and measuring its length, bend it , and measure the projected length of each arm after bending. The difference between cut length and the sum of the projected length is the gain, which is then factored in for each bend. We used to be able to bend tube into a rectangular loop to an accuraccy of 0.5mm for furniture frames using this technique.

Last time I took some bits to Glennsam for tig weld. He has quite a lot of benders in the shop and making handrails for living. Maybe give him a call to see if he could help? His name is Jeff.
039768 2400 - 473 Hammond rd, Dandenong South

ps: found his website http://www.glennsam.com.au/