DIY halfpipe sheet metal curving anvil
This simple DIY halfpipe anvil hand tool makes it simple to make smooth curves in sheet metal with a thickness in the range of 0.3-1.2mm.
Introduction
I have already posted on Rolling curves in titanium and stainless steel foils using a hand roller against foam rubber backing. When the thickness and or the width of the section being rolled increases, this method fails. This because the bending moment that can be applied by the muscles of two strong hands will eventually not be enough to make tight and uniform curves.
The current post is about making tubular shapes from sheet metal that is somewhat thicker 0.3-1.2mm thick.
DIY anvil sheet curver
Simple vice mounted curving anvil. A simple halfpipe anvil can be made by cutting off a short length (~100mm) of thick-walled pipe. The pipe can have a 10mm hole drilled into it to receive a length of 10mm rod that can be welded into place to form a long mounting stem.
The stem can be used to hold the pipe while it is cut in half to make the halfpipe anvil when gripped in a vice.
Lastly, all the edges and corner can be rounded to make it safe to contact and protect the sheet metal from ‘scarring’. A cloth lining can be used in the anvil if scratch prevention is important.
Using the curving anvil. With the stem gripped in a vice, the halfpipe will focus the bending moment that can be applied by a suitable piece of pipe. This method can apply much greater bending moments from much bigger body muscle groups.
It also will limit over bending of the curve. The bending moment can also be augmented by the application of gentle percussive forces to the pipe over the anvil. “Put simply, hitting the pipe gently with a hammer.”
“A sacrificial piece of wood can be used to protect the pipe from damage, or even better a crude wooden mallet can be used for the percussion.”
Such a bending action can be accurately targeted to parts of the curve that need more curving. This means that it is a little slow, but easy, to make the forming curve fully round.
Simple leaver action curving anvil. The above anvil can be made more convenient to use by mounting it on a length of timber. This timber can be held in a bench vice or similar when required for use.
A long curving pipe can be mounted on an adjustable threaded rod that acts as the pivot pint for the curving pipe/leaver.
The mounting rod below the anvil can be simply mounted in a long ‘sloppy fitting’ hole that can be drilled into the timber. The sloppy fit allows the anvil face to align with the face of the bending pipe to prevent bruising the sheet metal and apply the curving force where it is most needed. More mounting holes can be drilled (To a fixed depth.) along the length of the timber.
The mounting position along the length of the timber can be changed to vary the bending moment that can be applied by the leaver.
Also, the distance of the anvil from the pivot point will vary the length of the tube that can be formed as it is progressively worked along the anvil from both ends.
“From my limited use of the device, I don’t think leverage will be a limiting factor.”
[Add a video of easy ‘bump’ curving of 0.4mm sheet metal tube]
Discussion and conclusion
The description above is for a 40mm diameter anvil. However, a wide range of anvil diameters should work this way with the one timber mount with its pivot point with adjustable height.
I have found that bending action is good with the simple anvil and the mounting stem is essential for stabilizing the anvil. Otherwise, it scoots all over the place and was frustrating to use.
However, the timber mounted anvil was much easier to use. ” No, it was a delight to use. It was so easy that I have not needed to use the leverage of the system to date.
I have been able to gently bump the leaver up and down and move the forming tube along and around as, required, to make a delightfully curved tube. This was without any stress on my body or risk of injury.”
An ode to the wonders of DIY custom tools;
A good DIY tool is worth its weight in gold,
The work to wrought and safely hold,
Its short time to rend pays an endless dividend,
Like friends, worth their mg weight in feathers when old
Tim
