PDA

View Full Version : How do glass lathes work?



Alistair Hosie
06-08-2004, 08:03 AM
What are glass lathes and how do they work I know we had a post about them somewhere but can't find it ?I am fascinated by these things Alistair

pgmrdan
06-08-2004, 08:32 AM
http://www.big-list.com/glasslathe.html

Evan
06-08-2004, 11:20 AM
Here is a good link.

http://www.ecu.edu/chem/glassblowing/glasslathe.htm

The glass lathe is not like a metal lathe although it has a superficial resemblance. Scientific glass blowing is largely an additive process unlike machining which is subtractive. The lathe is used to rotate work so it can be evenly heated. It is also used to pull or push heated glass in a precise manner by moving the carriage on the right. That carriage is basically a movable headstock with chuck. The glass lathe has two of these, one on each end. The one on the left is usually fixed. They are motor driven and are tied together mechanically to stay syncronized. Cutting tools are not used and the glass is not machined or ground. The tools are a variety of torches and burners, graphite paddles for shaping molten glass, an assortment of picks and a breath tube that is usually connected to a rotating fitting on the right side of the lathe and used to allow the glass blower to apply pressure or suction the item he is working.

As an example I'll relate making a very simple part, in this case a small one-way valve. A piece of Trubore borosilicate tubing 1/4" OD is chucked up in both chucks. The lathe is turned on and rotating about 10 rpm. Flame is brought to the work until the glass is softened for an area about 1/4" long. The right carriage is jogged to the left a preset amount against a carriage stop which causes the softened glass to bunch up making a small constriction inside the tube. The work is allowed to cool and a file is used to score the tube where it is to be broken. The right chuck is loosened and removed and the valve is snapped off from the remainder of the tubing. If this is not a precision valve then a small glass ball is dropped into the tube to act as the valve body against the seat that was formed. If it is to be a precision valve then a steel ball on the end of a shaft is used with fine grit to grind the seat to a close fit to the glass ball. After inserting the ground glass valve ball the side of the tube is heated just above it and a pick used to slightly dimple the tube in order to retain the valve ball. The ends of the tube are flame polished to smooth them and the valve is done. I made a lot of these.