3' hollowing tools? And steel types

[Tymur Kharkivskyi]

Tymur.bending for me is never accurate, that is you are bending a tool for additional reach and as every form varies to some degree to the lesser or greater, so accuracy is not important. But bending, I do it with heat or a hydrualic press and some times both IE my 25mmx25mm high tensile tool rest I have to use both heat and a 10 ton press to do the bend, most of bent hollowing bars are smaller in dia 16,18,and 20mm. One way around the bending issue is to make a small flexible head that fits in the main bar. Other heads that a bent are generally for my internal scrapers and can swing left to right, some can be converted to a hollowing action.

Here is one that I have with 6mm dia tungsten cutter, I probably run/use half a dozen type of flexible heads . Some with multiple sections to simple 2 or 3 sections, all contain slicing type cutters some wit sheild some without.

Hughie, thank you! It’s like the principle of a motorcycle chain, but with a rigid connection. At least, that’s the first thing that comes to mind looking at this marvel. Thank you for sharing.

For me, every new day here brings new people and new ideas. I actually registered on the AAW back last year, but it’s only this year—now that I’ve started making things myself actively —that I decided to dig deeper. AI kept giving me tons of links to this forum for all kinds of questions. I realized I’ve lost a whole year when I could have been learning so much. Thank you all.)))

 

[Doug Freeman]

Here is one that I have with 6mm dia tungsten cutter,

What type/size chain did those links come from? That’s an excellent idea!

 

[John K Jordan]

Tymur.bending for me is never accurate, that is you are bending a tool for additional reach and as every form varies to some degree to the lesser or greater, so accuracy is not important....

When I want a certain curve in steel rod/strap, etc. I usually find something that will work as a mandrel, heat the section to orange/red with an oxy-acetylene torch, and bend around the mandrel. The hardest thing is sometimes devising a means of holding the end.

If bending cold, I have a 20 ton hydraulic press. With most steels, the spring-back in most steels requires overbending just the right mount. Can count the number of things I've shaped and repaired with that big press (from Northern Tool).

Note that to bend pipe and tubing to a certain shape, a common industrial method (also possible to do at home) is to fill the tube with sand, tap the sides to compact the sand, seal the end by welding a cap, heat and bend. The sand keeps the cross-section from distorting during the bend. I once worked at a place (Grinell Industrial Piping) where they would bend huge pipes for use in nuclear power plants under construction - I watched one 20' long maybe 18" dia steel pipe with a heavy wall bent with the sand method - they welded a steel plate on the end, raised the pipe raised until it was vertical, filled with sand, then hydraulic hammers pounded up and down the pipe for hours to compact the sand. Cap the other end, put the section to bend in a appropriate induction furnace and heat until orange/red, then place the pipe horizontally on a huge steel table and bend around mandrels by pulling with big ropes wrapped around vertical winches. All the workers had to wear fire-protection suits! (I was NDT and was just in the bending bay to gawk!)

I did inspection in another facility which did cold bending on stainless steel pipe with heat radiating coil fins welded over the entire length. They also filled with sand, vibrated from the outside to compact the sand, then bent cold around pre-formed mandrels. A specialty field for sure!

JKJ

 

[Tymur Kharkivskyi]

John, I was interested in how to bend a rod to make a 'bent' or 'extra bent' bar. Sand won't help here. My main question is how to make this process repeatable. Back when our house was being built, the workers brought their own bending machine and bent rebar with practically perfect repeatability. But with a 1-inch rod, that might not work the same way. Do you think the only option is to do it through heating?

 

[John K Jordan]

John, I was interested in how to bend a rod to make a 'bent' or 'extra bent' bar. Sand won't help here. My main question is how to make this process repeatable. Back when our house was being built, the workers brought their own bending machine and bent rebar with practically perfect repeatability. But with a 1-inch rod, that might not work the same way. Do you think the only option is to do it through heating?

Rebar is relatively weak, made from low quality steel. (I used to be an inspector for concrete used in industrial and commercial building construction.) A steel supplier once told me the steel that goes into rebar is junk.

Rebar is, of course, made to reinforce concrete, not generally from side stresses but to keep the concrete together and minimized self destruction from cracks from stress, weather, moisture, etc. In industrial situations rebar is built up in to "cages" with vertical and horizontal pieces, all wired together. (Never welded, since welding can create areas that can corrode in the presence of moisture.) Wooden forms are built around the columns and such, the concrete poured or pumped in from the top, then special vibrators

Relatively easy to bend without heat but easier and more controlled bends with heat. I've used 1/2" diameter rebar for many things.