Custom rebar bending mandrel diameters

[user277418]

Hi

Quite a while, requirements to minimum rebar bending mandrel diameters have been changed in standards of my country. Let's say for 12 mm diameter rebar, it has been 4*12=48mm and now it is 4.5*12=54mm
Usually rebar bending companies have set of old mandrels for their bending machine and they don't rush to exchange them. I don't know where are from the mandrels come to the bending company. Does they come from bending machine producer or custom made? ¯\_(ツ)_/¯ So the question is actually to those who works in such kind companies. Is it easy to get mandrels of different diameters for rebar bending machine?

Best regards

 

[MotorCity]

Bending equipment is not my field of expertise, but I would think that the mandrel radius should meet or exceed the minimum bar bend radius specified by your country's concrete design code.

 

[PGMEP]

Hi there,
Usually the machines producers has already varius bending pins designed for the same diameter, since they usually sell worldwide and the standards are different between nations.
but they also make custom pins on demand, in case of table benders the pins are so simple that you can make your own very easily..
hope I've helped.

 

[SJBombero]

I think your options are to contact the manufacturer to see if they sell the new sizes or call a machine shop. I'm not sure how the different mandrels sizes work but it seems possible that larger mandrels could be turned down on a lathe to get the correct size and then you are left with only the largest one that has to be replaced.

 

[kingnero]

First gotte say according to what standard you work.
Rebar typically has low ductility (bars and coils are ~10-12%, the low ductility variety used for meshes is around 5%), too small mandrels can introduce cracking.
Eurocodes has very clear guidelines, so have the national standards concerning the different grades of rebar.

 

[user277418]

Hi

Thanks for the replies

in case of table benders the pins are so simple that you can make your own very easily..

That is how I see it too

I think your options are to contact the manufacturer to see if they sell the new sizes or call a machine shop. I'm not sure how the different mandrels sizes work but it seems possible that larger mandrels could be turned down on a lathe to get the correct size and then you are left with only the largest one that has to be replaced.

Usually rebar producers are not eager to make any changes. Any changes cost something after all. That is why I have started my "research" from here But, as you said, seems the best way is to call them directly.

First gotte say according to what standard you work...Eurocodes has very clear guidelines, so have the national standards concerning the different grades of rebar.

It doesn't matter for the answer to the question, but it is Eurocode. The minimum mandrel diameters have been increased, so no worries about cracking

Best regards

 

[SJBombero]

If all the minimum mandrel diameters have increased then you could theoretically machine down the next largest mandrel to the sizes you need and have to replace only the largest. If the mandrels are just a simple cylinder, a machine shop should be able to do each one in less than 1/2 hour.

 

[robyengIT]

pay attention that the external surface (in touch with the rebar) has to be hardened

 

[SJBombero]

robyengIT - Good point. If the existing is already case hardened you can either anneal the case hardening or machine it off. If the whole mandrel is through-hardened, it's going to be tougher to machine.