Reassembling the TB-3 tube bender and trying it out again

This machine seems to be badged as a "tube bender TB-3". Looks to be of Chinese origin, but no doubt there will be US suppliers (I bought this in Canada) who claim it was "made" (ie packed and shipped) in the USA. 

Note that a "tube" is defined by its outside diameter, whereas a "pipe" is defined by its internal diameter. For a pipe/tube bender, this is important, since the formers / dies are tailored to a specific diameter. Here we are talking about exhaust tubes.

The original supplier (Woodward Fab, as identified by the stickers on the product) is still in business. However, they seem to have blocked access to their site from where I'm sitting. Presumably you have to be in their local (USA) market to be allowed in. There's some irony there, given that they are almost certainly passing off generic Chinese products as their own, domestically produced items. Call me a cynic.

However, and perhaps rather bizarrely (not), the apparently exact same product is available from a wide range of suppliers. Here's one such that is based in the UK. It seems that a new example with 3 sets of dies comes in around £1000 including vat.

The Chinese packing box is visible in the background. I don't have a problem with that. Note that these boys (W Neal Services Ltd) don't claim they are made in the UK.

Instructions seem to be a little harder to find, although you might argue they are hardly neccessary. Either way, here's a set of instructions and a parts list from one of the Chinese manufacturers.

SPECIFICATIONS
Model:	TB3
Maximum Machine Capacity:	2” (50.8mm) Capacity Mild Steel*
Dies Included (x 3):	1” (25.4mm) Diameter x  3” Radius x 120˚
	1 ½” (38.1mm) Diameter x 5” Radius x 120˚
	1 ¾” (44.5mm) Diameter x  6” Radius x 120˚
Die Centre Hole:	25mm Diameter
Pin Holes:	22mm Diameter
Maximum Bending Angle:	240°
Handle Length:	900mm
Dimensions – machine (apx):	1000mm x 600mm x 1080mm (l x w x h)
Dimensions – packaging (apx):	1200mm x 500mm x 520mm (l x w x h)
Weights – net/gross (apx):	64Kg/67Kg

Note that the factory supplied die sets have a bend radius that is largely proportional to the tube diameter. That's fair enough. The reason mine are all the same bend radius is because I had to make my own dies up from a short length of steel that ended up being cut into 3 sectors of 120 degrees. I was buggered if I was going to machine the sectors down further - manually machining the circular grooves nearly killed me as it was.

I found these photos of the fabrication:

Let's get it assembled and ready for action:

The sector rotates with the swinging arm. The fixed part of the die set is anchored to the main frame. You can see that this fixed guide needs to be at 90 degrees to the main frame (like this) when a tube is installed and ready to go. I don't have a piece long enough to show that (yet), although that should change any minute now......

Hmmf. Finally I received the 304 stainless tubes. I ordered these on Wednesday with "next (working) day" delivery. However, they didn't ship them until Thursday evening (aka Friday in terms of working days) and of course the courier doesn't deliver over the weekend. So that's essentially a 4 or 5 calendar day turnaround, depending how you look at it. Not massively overimpressed. Usually metals4u ship promptly and I've timed my orders to avoid the weekend in the past.

And also I received some Chinesium expanding wall bolts (M12 bolts) to hold the frame down to the floor. Allowing this thing to tip over could give you a nasty bit of pain, weighing ~65kg as it does.

I've made some concrete worm holes using an SDS+ drill and a 20mm masonry drill. Luckily no steel mesh was found on the way in.

I preset the bolts using the impact driver and some cast washers.

There. I reckon 2 will suffice. Seems pretty solid.

As well as the 32mm and 38mm tubing, I got a 360mm length of 10x100mm 304 flat bar. This should be sufficient for at least 2 good flange plates, even allowing for some waste for clamping etc.

I also need a level extension for operating the bender. I previously bought some 2" thick wall tube when I was making a drawbar for the Tree lathe. It wasn't much cheaper to buy a shorter length, so I ended up with 3m of the stuff, cut into 3 lengths. One such length is still slightly too long so needed to be reduced a bit.

And let's see what happens.

That wasn't too bad - and certainly easier than when I used the machine on that thick tubing I got previously (~2.5mm wall thickness). Of course, it wants to swipe the tube across the bench and clear everything onto the floor. But I had to choose an orientation and this seemed like the best compromise, given that I also need to be able to swing the long handle, keeping my elbows clear of any hard, fixed objects.

This is the characteristic squashing of the inside radius that you get when bending thin wall tubing without an internal mandrel:

There's a bit of a crease where the end of the sector meets the tube:

Here's the outside of the bend.

That's fine really and pretty much as expected. I will be using Chinesium mandrel bends to fabricate the more intricate and tight bends, so the bender will only be used for the more gentle bends. 

Note that there is a minimum length that needs to engage with the fixed guide. I managed to pull the tube past the outboard end of the guide and this is what happens. No damage done but it's good to be able to characterise the behaviour in terms of what "lost lengths" I need to expect:

Looks like about 65mm from the end of the bend:

You can see where the welded seam is located here. Perhaps there's an ideal position to locate the seam when setting up a tube for bending.

Now I will await the arrival of my mandrel bends from China. These are a selection of 45 and 90 degree bends in 32mm 304 1.5mm tube. Currently they appear to be waiting departure at the airport, somewhere in China.

In the meantime, perhaps I will get on and prepare to machine a couple of those flange plates. It's been a while since I use The Shiz (or in fact any of the CNC machines), so it will be good to blow off some of the cobwebs and make some chips.....