Technical Reference

Engineering considerations and maintainance techniques for traditional tailor's shears

Excluse use of tailor's shears on fabric
There is good reason to control the use of traditional tailor's shears for cutting fabric and not allow them to be used for any other purpose.
The fibre size in natural fibre fabrics (wool and cotton etc ...) and many of the synthetic fabrics used in clothing is far finer than materials like paper, cardboard, sheet rubber and many other materials. The slight blunting of a pair of shears after cutting incorrect materials is not determined visually without a digital microscope but the effect is to lose the microscopic raised burr that good condition blades have and while you will not notice the effect on paper or other non compatible materials, on fine fibre fabrics they will feel blunt and risks dragging fabric down between the two blades.

This is a high magnification of the cutting edge of a sharp pair of tailor's shears. While the inside face of the blade will appear shiny to the naked eye, under high magnification the bottom of the hollow grinding marks still show and the lapping of the top at the cutting edge has a finer finish to ensure that the blades when first sharpened do not notch against each other. Importantly there is a fine burr that is maintained at the top of the cutting edge by the design of the hollow ground inside face of each blade where each time you open the shears to cut, the burr is dragged upwards.

This is the top edge of a correctly sharpened pair of tailor's shears. The serrated finish is necessary to prevent slippage of the fabric while cutting. It is a mistake commonly made when touching up a pair of shears manually with a hand oil stone where the serrations are lost and often the precision controlled angle is altered.

Manually touching up a pair of shears
The correct technique to manually touch up a pair of shears that are starting to become blunt is to use a hand held oil stone across the blade at about 90 degrees going from the outside edge of the blade towards the inside edge of the blade while maintaining the correct blade angle. You will know when the blade is sharp again by being able to feel the burr on the inside blade face with your fingers. When you have succeeded in doing this, hold the tips slightly apart while closing then hold the blade together and open them which drags the burr upwards. Do this a number of times then carefully close them normally to see if they do not grab or bind, then test the shears on some fabric. It helps once the shears appear to be sharp again to do some test cutting on some of your scrap as it helps to bed the two cutting edges against each other.

The cutting edge angle
This will vary from one brand of shears to another. Due to their rigidly controlled hardening and tempering techniques, Wiss inlays are highly uniform and reasonably ductile in their hardened and tempered state. While old shears were usually sharpened at about 15 degrees, as long as the shears are only being used on fabric, Wiss shears can routinely be sharpened to between 30 and 45 degrees. Heinisch shears were made to an earlier technology that had less precise hardening and tempering which varies from pair to pair.

A good pair of Heinisch shears can also be sharpened between 30 and 45 degrees but some pairs have inlays that are too hard and are brittle so if they are sharpened at a high angles, the edges produce micro-chipping that under a microscope show small chips missing from the cutting edge. This cannot be fixed and you are limited to about 15 degrees.

Pairs like this are not well suited to tailoring. Most other brands, Wilkinson, Solingen types, Kissner and most other professional shears do not have this problem. Something that is important with any pair of professional shears is never overtightening the hinge or you create premature wear that shortens the life of the shears. With old viable pairs of Heinisch shears it also risks the problem of micro-chipping.

Matching the tips
This is a high magnification of a correctly matched pair of blade tips. When closed the tips match exactly which means the shears can be used to cut to an exact location in the cutting layout, a characteristic very useful for corners, notching and cutting darts. The bottom tip is carefully radiused to ensure the tips do not dig into the cutting table and don't snag fabric when cutting between layers. It is worth making the point that it is better to use a pair of trimmers for tasks like notching so you don't produce premature wear at the tips of larger shears.