Volvo Amazon 1965 (Volvo 13134)

[MrCrankyface]

Time for the next iteration.. I think this will be the one I use on the "real" piece.

Milled, sanded and polished a die and pressed it onto an old shaft for the air chisel.
Required some tweaking of the point to get it sharp enough to stretch the metal but dull enough to not punch too deep.
Surface finish is much better than previous attempt.
The die most likely needs to be hardened since the tip gets flattened out relatively fast, too fast if I want to do several of these.
Will probably try case hardening it since it's some random low-carbon construction steel.


After I was done hammering I tried pressing it the final stretch to see how it'd react.
This went quite easily, never going above 7 tons and no warping of the metal.
It developed some cracks in all 4 bottom corners due to overstretching, I can most likely avoid this by not hammering the corners as much and starting my hammering passes from the middle out.
Furthermore I will decrease the depth of the bottom die a bit as it's excessively deep at the moment.
Overall it's insane how much stronger these pieces become with just a shape like this, I should really press them and see how much they can take!

 

[MrCrankyface]

Alright so time for the little adventure of hardening the tool for the airhammer.
It's most likely made from S235jr or equivalent alloy and thus can't be easily hardened due to it's low carbon contents, so need to fix that..

First making a mix of crushed briquettes and 5%(by mass) sodium bicarbonate.


Welded a bottom on some tube and made a lid for it.
Filled it to the top with the coal mix and put the tool in the middle, plenty of coal around it to draw from.
Packed it just enough so things wouldn't shift around, don't want to compact it too much.
Had it in my furnace for around 7 hours total but first hour was ramping up from 15C to 750C-ish, following 6 hours it averaged around 930C.


Once my timer rang I broke the wire on the box, opened the lid and took the tool out and quenched it in oil.
After some cleaning with some 'scrotch brite type' of pad, this is pretty much what it looks like.
Tried running a file along the top curve there, all it did was polished up the surface, so carburizing and hardening definitely worked well!


I sanded the surfaces from 120 to 1500 grit followed by a thorough polishing.
After this I let it sit in the oven @ 200C for 2 hours which gave it this slightly yellow tint.
Hopefully this will hold up longer than it previously did so I can finish all the beads.

 

[MrCrankyface]

Spent a long time just trying to lay out where I wanted the beads. Dividing things into equal lengths can be deceptively hard when you're tired ...
I rather spend all this time with markers though than find out my mistakes when it's too late.
The aim is to layout the beads and predrill 3 holes for each location, another 3 holes can then be drilled with the form clamped onto the sheet so it can clamp evenly with 6 screws.
I tried doing this as accurately as possible so the beads don't look crooked next to eachother, but we'll see how that turns out later.


Some final adjustments to the form was made. The top has been planed down around a millimeter, this should make the top radius better.
I also added a shim in the bottom of it to offset another 4mm, so total will be 5mm less deep shapes.
Rough calculations indicate that this should equal ~20% less stretching needed so hopefully less prone to cracking.
It's still an area increase of 37% so I think I will try to anneal it after the initial hammering, before doing the final push in the press.
Hopefully that should normalize the grains so it becomes more ductile again.
All that's left now is to actually do the work ...

 

[brino]