How to cut metal with a guillotine

(Last modified: March 21st, 2019)

Guillotines cut metal by using 2 blades; one is fixed under the workpiece, the other moves downwards to cut through the metal. Guillotines come in many different sizes and are known by an array of names such as; guillotine shear, plate shear, squaring shear, Beverly, and throatless shear, but essentially, they all utilise the same mode of cutting.

cnc guillotine metals4U

Guillotines are available in mechanical, pneumatic and hydraulic models for use across a wide variety of projects. Hand or foot operated models are a useful addition to the hobbyist or DIY enthusiast as they make light work of cutting through aluminium, bronze, brass, and mild steel without the need for a large workshop or financial investment. For the metal worker needing fast and multiple sheets cutting regularly, a larger CNC pneumatic or hydraulic model would be more appropriate.

The cut edge of the metal may need deburring or finishing after being cut with a guillotine, this can be done with a mill file or an aluminium sanding sheet.

The different types of guillotine are looked at more closely below.

Squaring shear, power shear or guillotine.

This is most commonly used in industry as a hydraulically powered CNC machine, although they are available as foot or hand powered units. Guillotines can have either a fixed or variable cutting angle that reduces the risk of metal becoming trapped in the blades, although setting this ‘rake’ angle will compromise the exact squareness of the cut edge- this can usually be set to between 0.5° and 2.5°.  The force of the cut can also be reduced by adjusting the ‘shear angle’; this alters the rocking action of the blade to increase the stroke- this makes the cut from one side of the metal to the other as more of a scissor action than a chopping action.

Tips for cutting metal using a guillotine.

  • Eye protection and gloves should always be worn when cutting metal to provide protection from cuts and metal splinter injuries. Guillotines powered by electricity are incredibly noisy so ear protection should also be used.
  • Adjust the settings on the machine by following the manufacturer’s instructions to the desired length of cut, shear angle, and rake angle.
  • Ensure that all guards are in good working order and correctly in place. The blade and clamps should be correctly isolated by the guards to avoid entanglement. The force used within guillotines could sever a limb, so do not rush the machine set up or ‘make do’ with any element of the equipment that is not fit for purpose.
  • Place the metal into the front of the machine and feed it through until it touches the back gauge then activate the clamps to secure the metal.
  • Engage the blade mechanism which may be a key pad, treadle, or lever depending on the machine. The blades will shear off the metal which will drop into the collection chute to the rear of the machine.
  • If the metal does not drop out from the machine, do not try to free it manually as the blades may be jammed against the cut off metal, removing the metal may cause the blades to slam closed or the metal to drop suddenly causing catastrophic injury. Switch the machine off and call a qualified engineer to clear the machine.

Throatless shear, Throatless guillotine.

Throatless guillotines have no plate in front of the blade to support the metal and no ‘throat’ to dictate a particular way the metal must be fed into the blades. This configuration makes it easy to manipulate the metal easily into the cutting blades. The blades are raised and lowered into and out of the metal by a hand operated lever.

How to cut metal with a throatless guillotine.

  • Ensure eye protection and heavy-duty gloves are worn.
  • Mark the metal with marker pen, or a scoring scribe, along the cut line.
  • Feed the metal between the blades and lower the lever in small or long drags to make a series of short snips or longer cuts while continuing to manipulate the metal into place; this simple technique allows almost any shape to be cut from sheet metal.

Bench shear.

Bench shears are mounted on the workbench to provide a secure working environment. The lever operated mechanism provides a forceful cutting action. Bench shears can be used to cut out rough shapes and straight cuts in sheet, however, they are not suited to the more intricate cutting that is achievable with throatless shears.

How to cut metal with bench shears.

  • Ensure correct PPE is worn.
  • Measure and mark or score the cut line if necessary.
  • Place the metal between the blades and pull the lever downwards to engage the blades and push it back into an upright position to open the blades.