Stick radius tool for tube bender die

petcnc

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I need to bend a 20mm stainless steel tube 180 degrees to 40mm radius so I must make a die for that.
I had a 10cm cast iron wheel that could be used as it is machined fairly easily using my mini lathe.

DESIGNING

The hardest thing was to design a stick that holds a cutting tool that would be fitted to the mini lathe and create the radius needed for the tube.
The idea to machine it directly does not apply as the material for the die (purple in the photo) is too large for my minilathe to be machined directly with a lathe tool. Moreover it is very hard (for me) to make a radius without some specialized tool.

TP and diet.jpg

Initial idea was to make a stick style rotating tool that holds an insert and will be supported at the side of the tool post (blue at the next sketch)

TP stick1.jpg

That was a poor idea that proved to be of no practical use as the tool, in order to be solidly and firmly supported by the tool post, could not be at a distance from it. When testing it the tool was too close to the toolpost to be used for the purpose.
After some head scratching the best idea that came was to do as with my right cutter! Whenever I have something big the LH cutter cannot handle I use the RH cutter. Similarly I could support the tool at the back of the toolpost to make it solid and give it the proper distance to be of practical use for the purpose.

TP stick2.jpg

As the tool had to be strong some fairly thick (for a minilathe) steel had to be used

TP stick3b.jpg

The cutter stick will be fit in the hole with the insert in the right height and it will be turned by hand. Some calculations ensured me that Th tool will be in the right distance to work the die.

TP stick3d.jpg

CONSTRUCTION

I gathered the metal

IMG_20200326_parts.jpg

Prepared the stick and the base

IMG_20200326_Stick & base.jpg

Welded the parts together

IMG_20200326_Welded0.jpg

Testing on the toolpost

IMG_20200326_Welded1.jpg


Marking insert height

IMG_20200326_Height1.jpg

Making a square hole 6mm

IMG_20200326_insert.jpg

Rounding front side of the stick

IMG_20200327_Rounding.jpg

Fitting a handle and the tool is ready

IMG_20200328_Final_tool.jpg

Using it on the minilathe

IMG_20200328_In_use.jpg


Results were great! It fits nicely the old tube so I can bend the new one.

IMG_20200328_End.jpg

Thanks for reading
Petros
 
Last edited:
When theirs a will you find the way. Good job on your success!
 
B-R-I-L-L-I-A-N-T! :applause 2:

Petros, thanks for sharing this!

When I have been faced with a job like this I've used:
i) a form tool (that's wide and chatters like crazy) and then a lot of filing _or_
ii) tried to use the two feed handles like an Etch-a-Sketch and trying to draw an arc (another thing I apparently cannot do!)

Your creativity is inspiring.
-brino
 
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