Bending tube (ram/bow & arrow bender)

[Dee]

I know this topic has been done to death, cant really find one specefic to my problem though...

I was practicing bending some tube so i can start making some barwork, and found that when bending the tube is "streched?" How do you mark the center of a bend (to line it up with a centerline at the top of the die) and also take into account the stretching of the tube so that the bend starts & finishes in the right place? Any tips/tricks or information I can use as a guide to know how far to "offset" the start of the bend for different angled bends...?

Ive read the pirate bending thread which is helpful, but only really applies to "pull through" style benders, where you can mark the start of the bend on the tube and line that up directly on the die, which cant be done on the bow and arrow style...

[johno88]

This might help.
http://www.diyfaq.org.uk/plumbing/Pipe% ... BillP).pdf

[MART]

Hey mate , mark a piece of pipe 1000 mm arround the pipe , then put it in the bender and line the mark in the centre of the die , directly opposite the ram , then bend 90 degrees , then remove and measure from the end off the pipe to the inside of the bend , this will show you how much you lose on bends. Then when you want bend in a particuliar spot , take off the loss and it should end up in the right spot , when doing two bends to make the pipe a U shape put a level on the bender when laying on its side , level it up along the ram , do the first bend and when setting up the second bend put the level on the bent leg and make it level with the bender , this will keep the bends parallel , Cheers Paul.

[Spartacus]

Hey mate , mark a piece of pipe 1000 mm arround the pipe , then put it in the bender and line the mark in the centre of the die , directly opposite the ram , then bend 90 degrees , then remove and measure from the end off the pipe to the inside of the bend , this will show you how much you lose on bends. Then when you want bend in a particuliar spot , take off the loss and it should end up in the right spot , when doing two bends to make the pipe a U shape put a level on the bender when laying on its side , level it up along the ram , do the first bend and when setting up the second bend put the level on the bent leg and make it level with the bender , this will keep the bends parallel , Cheers Paul.

yep

[want33s]

Here you go Dee,
Bending made sooo easy.... http://www.pirate4x4.com/tech/bendin_tube/index.html

and pipe notching without a big $$ notcher.... http://pirate4x4.com/forum/showthread.php?t=456800

[Dee]

Cheers guys,

but ive actually already studied most of those links. What I was looking for was something similar to the table in the link posted by johno88 but for 1.5, 1.75" tube etc...
This is because the pirate thread etc refers to using a "pull through" style bender, which makes it easy to line up the mark on your pipe for the "start of the bend" with the mark on your die for the "start of the bend". This is impossible to do though on the bow&arrow (ram) style bender because the only point you can align on the die when putting the pipe in is the centre of the bend.
Finding the center of the bend is what I'm having trouble with, because using the ram type bender actually deforms the pipe and what you thought was centre actually ends up 25mm further around the corner when you go to line the bend up with your markings on the floor...

Thanks for the tip MART, been using the level trick already, works a treat.
What your saying about the 1000mm though, by measuring to the "inside" of the bend, do you mean to measure to where the bend actually begins? Also, is this distance of pipe loss directly porportional to how many degrees you bend the pipe? IE will you lose twice as much on a 90* bend to what you will lose on a 45* bend?

[chunderlicious]

what i found while bending is that when doing say a roll bar, i take all three measurements for the bar then use those measurements for the bend centres maybe im lucky but ive done 1 bend wrong so far and ive done quite a few

[Dee]

what i found while bending is that when doing say a roll bar, i take all three measurements for the bar then use those measurements for the bend centres maybe im lucky but ive done 1 bend wrong so far and ive done quite a few

hehe righto, sounds easy! cheers mate.