Drop Machine
Tip Shapes
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Making Glass Instrumental Insemination Tips

Four Glass Tips Use any available glass tube of between 1.5 and 3 mm diameter. (This can be drawn down from larger diameters by hand, but requires a bunsen burner or gas torch.)

German "green band" capillary tube is considered the best for this purpose and is available in 100 mm lengths, it is 2 mm outside diameter, wall thickness 0.436 mm, inside diameter 1.128 mm and thus the area of the bore is 1 mm2 giving a total volume of 100 µl, ie 1 µl per mm.

This tubing is available from laboratory supply houses (visit them and explain your requirements as they normally will not deal with individuals).

Other types of glass capillary tube can be used as type is not critical.

A laboratory clamp stand can be utilised with a fixed clamp and a sliding one to grip the two ends of the capilliary. The lower sliding clamp can have various weights hung on it and the drop height adjusted using wooden blocks.

A description of the version I am making is on the drop machine page along with links to other examples.

The melting of the glass is provided by a small coil of NiCrome wire heated by passing current from a 12 volt battery or a car battery charger. (A variable voltage supply is useful here). For profiles that can be used see tip shapes.

A tungsten carbide scraper or planer blade can be used to nick the surface of glass to provide a "notch" that facilitates snapping. The point at which the nick is made can be located using a "gauge wire" O.15 mm diameter, with end face ground at right angles to the axis. This gauge is introduced from the open end. The gauge wire will only enter until it meets it's own diameter inside the taper, thus the nick can be made on the outside of the glass at that point.

Initial polishing, and some shaping, can be acheived using many items from the Dental Laboratory... Pumice powder... Diamond impregnated rubber discs (used in a Dremel Tool or other high speed grinder).

Final polishing should be achieved using a flame.

This process may initially seem technical, but anyone with a modest amount of skill and dedication can make top quality tips at a fraction of the cost of buying "ready made" ones... The process is also enjoyable and when completed you have the satisfaction of knowing that it was "all your own work".

 Written... Date Unknown, Revised... 23 October 2001, Upgraded... 22 August 2006,
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