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Author: Subject: Forming ally sheet
myke pocock

posted on 27/12/13 at 10:23 PM Reply With Quote
Forming ally sheet

Now that I have my Type 9 gearbox installed and almost up and running I need to do something with the bonnet. As the engine is now about 30mm further forward and slightly higher the bonnet touches the top of the eingine and I need to put a discreet bulge in it. I dont want to cut a hole and rivet something on so how do I slightly form the alloy and make a nice job of it. Any hints and tips or articles on the subject? Cheers.
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posted on 27/12/13 at 10:51 PM Reply With Quote
see this thread for what CAN be done

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richard thomas

posted on 27/12/13 at 11:08 PM Reply With Quote
For what it's worth, and by no means as technical as the above link - if you rub some basic white soap on the alloy and heat the alloy with a good hot flame until the soap turns black you will have softened (annealed) the metal enough to be able to beat/form/other it into shape....should be ample if you are only looking to make a slight change in profile. I would suggest a wooden buck and hammer it into the alloy sheet with the other side supported in a sandbag to help the re-shaping?
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mark chandler

posted on 27/12/13 at 11:41 PM Reply With Quote
To make a nice job you really need an English wheel, your local college may have one.
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posted on 28/12/13 at 01:26 AM Reply With Quote
Mkye we have sand bags bossing mallets and brazing hearth to warm it up in Carlisle ( but no English wheel) and back in on 6th I if you don't get it sorted before then
Mike (cut and paste this dodgey link)

Our most recent pics are here:

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posted on 28/12/13 at 08:39 AM Reply With Quote
A sand bag and a wooden mallet is indeed the way to go. (If you have no wheel)

However, use a hammer in good condition or you just make work for yourself.

When the desired shape is achieved turn over and finish off by chasing around the base of the bulge
with a nylon or hard wood chisel. This crease sets off the bulge shape rather than have a gentle blend in,
and looks far better for having a distinct finish.

Finish off with the various grades of wet & dry, and polish.

Paul G

Edit to add photo. (sorry but the bulge doesn't show very well)

[Edited on 28/12/13 by 907]

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posted on 28/12/13 at 01:56 PM Reply With Quote
John Bonnet posted a variety of different threads on metal forming techniques which I, with his permission, gathered together into a PDF file to make them more easily accessible. That document can be found here .

There's a few different examples of bonnet bulges shown in the above.


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