SPI Supplies Brand Glass Breaking Pliers for Glass 5 or 6 mm Thick

We would expect that most viewers of this page might think that there is some kind of typo or other error in the price! But we can assure you that there is no error. We have also made some further improvements to the SPI Glass Breaking Pliers and now we can truly call them "new and improved". The blackened handles are the result of the forging process and also contribute in a positive way to the "feel" of the handles when being used.

It is of course difficult to make these super high precision pliers look, in a website photograph any different from those that might be purchased in a local hardware store (and for a fraction of the price). Yet anyone who has used the SPI Supplies^® Glass Breaking Pliers will attest to the fact that such quality and precision is indeed required in order to get the best possible glass breaks and therefore also the best possible triangular glass knives.

And remember that the real purpose of these special pliers is to permit someone who does not have an actual knife maker to still make knives, though they will not be made with the same convenience and consistency of end result. Someone who already has a good well-functioning knife maker probably does not have a need for these pliers, unless they want a pair for either student use or use in an emergency, when the knife maker might not be working.

What makes these glass knives so different from those made with an ordinary pliers:
Quite simply, the gripping surfaces, when "clamped" down on a glass strip, give a three point loading system. They are made this way through a careful precision machining and finishing process. The benefit to the end user is also a dramatic reduction in the amount of glass that gets wasted because of knives made that are of unacceptable quality and therefore can not be used. The pliers are optimized for use with nominally 6 mm glass, which in, reality, if actually measured is more like 5.8 mm. The composition of the pliers is the highest quality of hard tool steel.

Normal glass pliers have straight jaws and do not give the "three point loading system." They are made for pulling glass apart, not for glass breaking. One just does not get the kind of edge that could be suitable for use as a microtome knife.

Hence, the SPI Supplies Glass Breaking Pliers make possible a break that is precisely 90° to the edge of the glass strip. Although we so far have not quantitatively defined the standard deviation of the angle around 90°, there is clearly a night and day difference in the yield of good knives when this pliers is used relative to "ordinary" pliers (and which cost far less). The quality of the score on the glass, along with the accuracy of the score itself, makes a big difference.

How does the final knife edge compare with that made from a knife maker?
One will be able to make a knife for histology applications, but not thin section applications, and while some of the knives will be of comparable quality, the yield will be lower, just how much lower depending on the experience of the operator. We do want to make sure that any prospective customers of these pliers appreciate that while the initial outlay for the pliers will be a whole lot less than for a Ralph knife maker, for once a year classroom demonstrations, these pliers could be all that is needed.

The best knife is made by always breaking the glass in half until there is a 1" x 1" (25.4x25.4 mm) square. The best triangle is made by getting applying the score line such that that there is an equal mass on each side of the score before breaking (with the pliers).

Recommended glass strips:
Naturally we recommend our own SPI Supplies brand of microtome knife glass be used for the best possible results. But one could expect to get good results with other brands of microtome knife glass. Just be sure that you are using this special glass, and not ordinary float glass from a local glass store, because if you do, you will unfortunately be very disappointed.