It does work - thats fine.
I had the whole report written and already pushed the "post" button. Then I immediatley thought I might better copy all the stuff I had written as the website was not responding immediately.
All fine until then.
But the mistake after that was that I copied something somwhere else and when I noticed the server was definitely not responding, I had only a small passage of a text I had written for somwhere else.
Half an hour just gone for nothing
Well - I hope I do it better tonight:
After quite a long break(7 weeks) , I started again with the cochran boiler. The firedoor will have a flange around the fire door that carries the hinge and the latch. To find out what shape I had "created" when making the fire hole tube, I first made a paper ring to see if the dimensions were in about right.
The easiest way would have been do machine that ring out from a piece of brass tube with a wall thickness of 4mm. But I did not have any brass tube like that.
So what - I decided to bend it from a piece of flat stock.
If you want to bend 4mm thick flat material, you need some kind of a fixture because just using the hammer wouldn't really work like it does with 1mm brass sheet.
I decided to make a die, you can see how I machined the hollow part of it (
Using my new clamps!)
The convex part of the die is a round piece of aluminium machined to 60mm. Then I annealed the piece of brass and pre-bent it cold. Naturally there was quite some springback and I will have to bend again. For the second step of bending, I decided to bend the brass when it is hot. So I heated it up to cherry red and put it in the die. This turned out well, you can see that the vise has been released again and the die is still closed
I used the convex part of the die clamped in the vise as a superglue chuck to machine the ring. The ring shape is by the way generated by different radii. That makes it possible to machine that shape on the rotary table.
Then I positioned the vise to the right place on the rotary table, using the bore in the center of the part to relocate the center of the ring (and also to move the workpiece so the radius center was right on the center of the rotary table). The X-direction could be made by moving the part in the vise, the y direction was realised by moving the vise along the 124 blocks.
Then the outline is completed, the opening just startet with one radius done.
Not long and it looked like what you can see on the left picture at the bottom.
I am really happy with the result, which is by the way the second attempt. The first one went wrong on the second radius which I somehow machined too small. I have now Idea how exactly that could happen, but I was really pissed off - especially because I though that I would have to remake the convex die too. Luckily it was not so and then I acutally was quite the second time.
The ring only required very few sanding with a small dremel sanding drum to fit it to the boiler. I really like how it turned out (though it is not finished yet...).
Cheers Florian
