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plunger
04-29-2015, 02:01 AM
I am trying to make a bending machine to bend 90 degree bends in 18mm x1.5mm stainless tube. I have machined the dies and they came out beautiful but it was an epic fail.
I was working on approximately three times the diameter of the tube. Am I doing something wrong. Does 3D actually mean if I machine the die to exactly half the pipe my die would have an outer diameter of 54mm This just looks too tight.
I am also wondering how difficult it would be to make a mandrel die bender,
What would the minimum size bend I could make successfully in a home shop be?

boslab
04-29-2015, 02:39 AM
I'd look at a Hilmor pipe bender for die size, it's close to what you need
Mark

Boostinjdm
04-29-2015, 02:43 AM
I think the radius of the die needs to be 3D.

If I read that right, then you made the diameter of the die 3D. Or half the size it should have been. I could be wrong though. Stainless can be tricky to bend.

astroracer
04-29-2015, 06:01 AM
You should have just updated this thread. My last post gave you the info you needed...

http://bbs.homeshopmachinist.net/threads/66667-tube-bending-dies

Pro-Tools minimum CENTERLINE Bend Radius for 5/8" & 3/4" OD tubing is 2" (50.8mm). That's the BEND RADIUS. Your die should be at least 4" (101.6mm) in diameter for the radius to be 2" to the centerline of the tube.
Mark

plunger
04-29-2015, 01:20 PM
Mark I have misunderstood the clr concept. I have made my die 64mm.If I insert a pipe in it the depth is exactly half the pipe.Is this not the clr.?Then I am actually 10mm bigger than what is regarded as minimum.
Meant to say pipe is 19.05mm(3/4?) and not 18mm

garyhlucas
04-29-2015, 01:36 PM
Plunger,
Go to the Hossfeld bender site and take a look at the tube die sets they sell to see how they are designed. I used to bend a 3/4" sch 40 aluminum pipe on a 2-1/2" center line radius with a Hossfeld.

Black Forest
04-29-2015, 02:11 PM
Mark I have misunderstood the clr concept. I have made my die 64mm.If I insert a pipe in it the depth is exactly half the pipe.Is this not the clr.?Then I am actually 10mm bigger than what is regarded as minimum.
Meant to say pipe is 19.05mm(3/4?) and not 18mm

I believe the CLR is the radius from the center line of the pipe to the middle of the bending die. If so your bending die is too small of a diameter maybe.

LKeithR
04-29-2015, 02:25 PM
Mark I have misunderstood the clr concept. I have made my die 64mm.If I insert a pipe in it the depth is exactly half the pipe.Is this not the clr.?Then I am actually 10mm bigger than what is regarded as minimum.
Meant to say pipe is 19.05mm(3/4?) and not 18mm

The centreline radius of the bend should be a minimum of 3X the diameter of the tube. The depth of the groove in the die should be 1/2 the dia. of the tube so that at least 1/2 of the tube is supported. If your tube is 18mm then the centreline radius should be minimum 3 x 18mm or 54mm. The OD of the die will be double that...108mm. And remember, the 3X D is just a guideline--some tubes will require an even larger radius to bend without wrinkling...

plunger
04-29-2015, 03:17 PM
Thanks guys .I will need to make another die but it was good practice. I was trying to find homemade mandrel bending dies and there is very little info.
One of the components is called a wiper die and it looks like a complicated thing to make on a manual machine.
I made my bender more of a compression bender as opposed to a rotary bender so back to the drawing board for me.
One thing I need to figure out is how to make the shoe,either I drill it into a rectangular block and split it or buy a 3/4 inch ball end mill or try to cut the radius with a boring head but I think chatter would be a big problem. Any ideas?

J.Ramsey
04-29-2015, 03:40 PM
Ball end mill would be the easiest method for the shoe.
I used the ball end mill along with a rotary table to make the die also.
Little bender I made for doing 5/8" x .049 tube on a 2.250 radius.
http://i.imgur.com/XFNoDFc.jpg
http://i.imgur.com/t884nU5.jpg
http://i.imgur.com/XQN71Nr.jpg

plunger
04-29-2015, 04:32 PM
That is real slick looking.Is that piece on the die welded on and then machined with a ball nose to be blended in. Is that what they call a compression bender. It looks like the die is stationery. I have never used a ball nose end mill before, does it cut well or do you rough it out as close as possible first.?

J.Ramsey
04-29-2015, 04:54 PM
I burned a circle from 1-1/4" plate to approx size, turned dia and roughed the groove depth then used a rotary table and the ball end mill to finish up the radius.
Then I ran the ball end mill down a piece of 1-1/4" square stock and cut that in half then bandsaw cut a notch out of the round and welded one piece on for the tail and used the other half for the shoe.
It took the better part of the afternoon to make the bender.
Here's the first rack I bent up with it.
http://i.imgur.com/zQ5qHx7.jpg
http://i.imgur.com/8uARJnT.jpg

plunger
05-05-2015, 05:27 PM
This looks like it could be made in a home shop
https://www.youtube.com/watch?v=bMZFa1Iae2w

boslab
05-05-2015, 06:08 PM
Mr Ramsay that's a very nice job, neat
Mark

ezduzit
05-15-2015, 12:10 AM
Really nice job.