Which type of metal guillotine is best for your fabrication workshop?
- Peter Dawber
A metal cutting guillotine? A guillotine shear? A sheet metal shear? A power shear? Known by many names these machines shear carbon and non-ferrous metals by means of a pair of blades set one above another, with either a fixed or adjustable blade gap, and driven mechanically, pneumatically or hydraulically. The blades will have a fixed or variable cutting angle – known as the rake angle – depending on the application they have been designed for. A variety of designs are available including manual foot operated or treadle guillotines, direct drive mechanical models and hydraulic designs in both swing beam and variable rake variants.
So given the variety of designs available, the question I will attempt to answer here is which type of metal guillotine shear will be best for your metal fabrication workshop?
For light gauge material and sheet metal;
Direct drive mechanical designs such as the Morgan Rushworth RGMS models are ideally suited to cutting from light gauge material up to 3mm or 4mm in mild steel. For lower capacity models a fixed blade gap is acceptable, however if you are cutting in the range from 0.5mm to 3mm, adjustable blade gap is needed to ensure a good sheared edge on all thicknesses and to avoid damage to the machine.
For heavier gauge and plate material;
If you are processing plate of around 5 or 6mm and above a hydraulic machine is normally best although high capacity mechanical shears are available for thicknesses up to around 30mm for use in blanking lines at steel processors. For metal fabrication workshops however almost all new machines supplied are hydraulic guillotines although a number of heavier mechanical flywheel type guillotine shears remain in use; as a point of interest these designs have changed little from the original models driven by factory belt drive systems.
Swing beam shears;
For cutting 4, 5 and 6mm material and thicker plates up to a typical maximum of 20mm mild steel a hydraulic swing beam shear is commonly used. These models have a fixed rake angle which, in order to reduce power, is designed to cope with the heavier end of the stated capacity. For many applications this won’t cause any issues, especially if you are predominantly cutting thicker material towards the machine capacity or are blanking or trimming larger components.
Variable rake guillotines;
If on the other hand you need to cut a range of thicknesses from lighter gauge material up to heavy plate, then a variable rake guillotine – otherwise known as a guillotine shear – would normally be a the preferred option. This design also copes better with shearing thin strips where you are retaining the cut part at the back of the machine; a variable rake guillotine will reduce the likelihood of the cut part twisting or bowing. These models are available in plate capacities of 6mm up to 30mm and above; Morgan Rushworth offer a standard range with capacities up to 25mm and lengths up to 6 metres.
This summary should allow you to make a basic decision around the type of guillotine you need, however there is much more to consider including relative capacities of different materials, control types and different productivity options. I should also note that for all thicknesses stated or when referring to mild steel, I am assuming a tensile strength of around 45 kg/mm2 or approximately 440 MPa or N/mm2.
As you will understand, this overview is by no means exhaustive; I could explore much of the above in more detail and also dive into other guillotine topics, such as;
- A more detailed review of the advantages of a variable rake guillotine versus a swing beam shear
- What causes twisting, bowing or cambering in your sheared blanks?
- Which guillotine options would have the greatest impact on your productivity?
- Guillotine safety and maintenance; how many times can the blades be turned on your guillotine?
I intend to produce more articles covering these subjects over the coming weeks and months, so please keep coming back to this blog if you find this useful and interesting. In the meantime, happy fabricating!