Following many requests I am now adding detailed drawings of the
Magnabend centreless hinges to this website.
Please note however that these hinges are too difficult to make for a
The main parts of the hinge require accurate casting (for example by
the investment process) or machining by NC methods.
should probably not
try to make this hinge. However
may find these drawings
(An alternative style of
hinge which is less difficult to
make, is the PANTOGRAPH STYLE. See this
section and this
The Magnabend CENTRELESS COMPOUND HINGE was invented by Mr Geoff Fenton
and it was patented in many countries. (The patents have now expired).
The design of these hinges allows the Magnabend machine to be
The bending beam pivots around a virtual axis, typically slightly above
the working surface of the machine, and the beam can swing through a
full 180 degrees of rotation.
Magnabend Hinge Animation:
In the drawings and images below only
a single hinge assembly is shown. However in order to define a hinge
axis at least 2 hinge assemblies must be installed.
Hinge Assembly and Parts Identification (bending beam at
Hinge with Bending Beam in approx 90 degree position:
Mounted Hinge Assembly -3DModels:
The diagram below is taken from a 3-D model of the hinge.
By clicking the following "STEP" file: Mounted
Hinge Model.step you will be able to see the 3D
(The following Apps will open .step files: AutoCAD, Solidworks,
Fusion360, IronCAD or in a "viewer" for those apps).
With the 3D model open you can look at the parts from any angle, zoom
to see detail, or make some parts disappear in order to be able to see
other parts more clearly. You can also make measurements on any of the
The Mounting Block material is
AISI-1045. This high
carbon steel is chosen for its high strength and resistance to swaging
around the hinge pin hole.
Please note that this hinge mounting block is designed to be stabilised
by welding to the magnet body following final
Also note the specification for a shallow thread within
for the hinge pin. This thread provides a channel for wick-in Loctite
which is applied during hinge assembly. (The hinge pins have
strong tendency to work out unless they are well locked in).
4. Hinge Pin:
Hardened and ground precision steel dowel pin.
Diameter 12.0 mm
In the drawings and models above the hinge assembly is bolted to the Bending
Beam (via the screws in the Sector Block) but the
attachment to the Magnet Body relies on bolting AND welding.
The hinge assembly would be more convenient to manufacture
and install if welding was not required.
During the development of the hinge we found that we could not get
enough friction with bolts alone to guaranteee that the mounting block
would not slip when high localised loads were applied.
Note:The shanks of the bolts themselves do not
prevent sliping of the Mounting Block because the bolts are in oversize
holes. Clearance in the holes is necessary to provide for adjustment
and small inaccuracies in positions.
However we did supply fully bolted-on hinges for a range of specialised
Magnabend machines that were designed for production lines.
For those machines the hinge loads were moderate and were well
defined and thus bolted-on hinges worked well.
In the diagram below the Mounting Block (blue colour) has been designed
to accept 4 x M8 bolts (rather 2 x M8 bolts plus
This was the design used for the production-line Magnabend machines.
(We made about 400 of those specialised machines of various lengths mainly during
Please note that the upper two M8 bolts tap into the front pole of the
magnet body which is only 7.5mm thick in the area under the hinge
Thus these screws must not exceed 16mm long (9mm in
the mounting block and 7mm in the magnet body).
If the screws were any longer then they would impinge on the Magnabend
coil and if they were any shorter then there would be inadequate thread
length, meaning that the threads might strip when the screws were
torqued to their recommended tension (39 Nm).
Mounting Block for M10 Bolts:
We did some testing where the mounting block holes were enlarged to
accept M10 bolts. These larger bolts can be torqued
to a higher tension (77 Nm) and this, combined
with using Loctite #680 under the mounting block, resulted in
more than sufficient friction to prevent slipping of the mouting block for a standard Magnabend
machine (rated to bend up to 1.6mm steel).
However this design needs some refinement and it needs more testing but it is well worth pursuing.
The diagram below shows the hinge mounted to the magnet body with 4 x M10 bolts:
If any manufacturer would like more details about a fully
bolted-on hinge then please contact