Safety Emporium for all your lab and safety needs
Safety Emporium for all your lab and safety needs

*The Glassware Gallery*

Laboratory Clamps and Holders

Index  

Introduction

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Whenever one uses laboratory apparatus such as a distillation setup, a vacuum line, a Soxhlet extractor and the like, one needs to attach the apparatus to a stable support or frame. There are a wide variety of different kinds of clamps available. They are also available in a variety of materials, the two most common being nickel-plated zinc and stainless steel. Both are durable and resistant to most common laboratory conditions, but stainless steel will provide the greatest corrosion resistance and most durable surface (if you don't mind the significantly higher cost).

2- and 3-fingered clamps

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The three-fingered (or 3-jawed) clamp is a standard in most any laboratory. These feature a set of jaws or fingers that can clamp and hold glassware, and a cylindrical extension arm that allows one to vary the distance from the support. These come in a variety of sizes (usually small, medium and large):

a 3-fingered laboratory clamp

The small size is typically used to hold small thin cylindrical items such as thermometers and temperature probes. The medium size is commonly used for small jointed glassware in sizes up to about 29/42 and can also support small condensers in distillation setups. Large sizes are often used to support vacuum lines, large apparatus, and chromatography columns.

The double-adjust 3-fingered clamps shown above feature a set of thumbscrews to adjust the jaws. As shown, these usually have wide pads to easily allow precise individual adjustment of either arm (the side with two fingers and the side with one finger). Some clamps have only a single adjustment and these usually feature a wing nut rather than thumbscrew. There is no real practical reason to chose single adjust over dual as the price difference is insignificant.

a 3-fingered laboratory clamp

Two fingered clamps usually feature two broad fingers to provide support. These are available in both single and dual-adjust styles:

a 2-fingered single adjust clamp a 2-fingered dual adjust clamp

Regardless of style, a clamp needs a holder to connect the arm to the ring stand or laboratory frame support. Some examples of these are shown below. The one on the left is the most common and sufficient for most needs, but there are a variety of styles, including ones that swivel to accommodate just about any position (click on any item for more information and detail):

a standard laboratory clamp holder a swivel laboratory clamp holder

an all-position laboratory clamp holder

Some clamps even integrate the holders for special purpose situations or ease of use. Some examples include clamps for holding thermometers on the wall of a water bath and fixed-position clamps that while not adjustable, provide a repeatable clamping position every time:

a 3-fingered water bath clamp a 3-fingered fixed position clamp

Chain and Column Clamps

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Larger cylindrical laboratory objects such as lecture cylinders, reagent bottles, beakers, chromatography columns, and small crystallizing dishes are often several inches in diameter and difficult to secure with a 3-fingered clamp. In these situations a chain clamp is ideal. They are available in two basic styles, one with a wide flange that helps keep the object from tipping, and a narrower-banded one:

a laboratory chain clamp another laboratory chain clamp

Both work with an open-link chain. To use one of these, the user pulls the chain tight around the object and hooks the link that most closely matches the necessary circumference on a tang or catch. Tightening a thumbwheel or thumbscrew then pulls the chain tight, providing a firm grip.

Column clamps are basically a common radiator clamp affixed to an extension arm. One threads the slotted metal strip into itself and then tightens the clamp with worm gear using a thumbscrew or screw/nut driver depending on the model:

a worm geared column clamp

Joint Clamps

Glassware joints come in a variety of shapes and sizes, and the clamps used in holding these together are discussed in our entry on joints.

Ring clamps and miscellaneous stands

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Open and closed rings are a common means of supporting laboratory apparatus. They do not clamp, per se, but they are used to stabilize or support items such as separatory funnels, or to hold beakers over open flames. Some are available with a PVC coating to cushion the glassware.

an open ring clamp

Round and square support plates are similar. The one shown here can be used to support a stirplate or heating plate.

a support plate

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This page was last updated Sunday, June 12, 2016.
This document and associated figures are copyright 1996-2017 by Rob Toreki. Send comments, kudos and suggestions to us via email.