TUBECRAFTER:
AMATEUR VACUUM TUBE MAKING
Copyright Ron Soyland
BASIC EQUIPMENT USED IN TUBEMAKING
To make tubes you must have certain equipment, and you will have certain equipment that would be nice to have but is not absolutely necessary. This is only a list of equipment, an overview. Full descriptions of each piece are given in other sections of this site.
GLASSBLOWING:
To work glass there are certain items that must be on hand and others that you might be able to do without. Here is a list of typical glassblowing tools and if you need them or can do without.
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VACUUM PUMPING: The degree of vacuum necessary for tubes is such that a vacuum SYSTEM is required.
The two types of pumps are manditory.
The inlet valve lets you open the system to air without shutting off the diffusion pump. This is not strictly necessary but saves considerable time when changing out tubes. The outlet valve is necessary to isolate the diffusion pump while roughing down the vacuum tube from atmospheric pressure. Without this valve, you would have to cool off the diffusion pump while you did the roughdown. Very time consuming. The vacuum system is described in detail in the section MAKING THE VACUUM in this website.
PINCHER WELDER: The main way electrodes in the tube are interconnected is via resistance welding. A hand held pincher with electrical contacts is used to clamp the two parts to be welded. A brief burst of electric current is passed to make the weld. This is an essential piece of equipment and will be necessary to have.
GLASS LATHE: Of all the equipment used in tube making, the torches and glass lathe are the most used. However, it is possible to get by without a glass lathe. It will take a LOT more experience at glassblowing technique. You can make up fixtures of wood and sheet metal to handle a lot of the setups, but it will be quite difficult to hold the parts of the tube in exact relation, sometimes as close as 1/2 millimeter spacing, while doing the seals. Unfortunately, the glass lathe is the most expensive tool in glasswork. If you plan to make a continuing practice of tubemaking, you should plan to have a glass lathe. If you are only going to make a few tubes and go on to something else, simply make tubes that can be made without a glass lathe. Several are described in detail on this site.
BAKEOUT OVEN: When pumping the tube to develop the vacuum, the air trapped in the glass and elements must be driven completely out to keep it from seeping out over time after the tube has been sealed off, thus ruining the vacuum. To drive the air out the tube is heated to 1000 deg. F while the tube is being pumped. This requires a small oven that can be placed around the tube while it is on the vacuum system. If you are making tubes that are expected to last longer than a day or two after being sealed off, the bakeout is absolutely necessary.
GETTER FLASHER: The getter is absolutely necessary if you expect the tube to remain good for longer than a few weeks. The getter is a small element containing a reactive metal such as barium. The getter metal is heated to evaporate it onto the inside surface of the tube envelope. This must be done while the tube is under high vacuum, so the heating must be done through the glass. This is done with an induction heater connected to a suitable coil that is held over the tube adjacent to the getter element. The getter flasher is available for around $400 U.S. or you can build one with parts from ebay for much less.
TUBE TESTER: This is not your standard tube tester like is used to test TV tubes. This is a metered power supply that allows you to adjust the various voltages applied to the new tube while watching the results on meters. This tester is not available commercially and would have to be homebuilt. You could get by without the tube tester by using portable bench power supplies and a V.O.M. to read the tube current. This would be quite inconvenient.
VARIOUS HAND TOOLS: There are various hand tools that are used in the working of glass, such as carbon prods, carbon flats, pinchers, wire holders, etc. These are necessary and very easy to make yourself. All the tools you would need to do the tube glasswork would be easily made up for under a hundred dollars, so these tools are not a problem to get.
GLASSBLOWING:
To work glass there are certain items that must be on hand and others that you might be able to do without. Here is a list of typical glassblowing tools and if you need them or can do without.
- NEEDLE POINT FLAME TORCH
- 1/4 INCH FLAME TORCH
- 5/8 INCH "ROSEBUD" TORCH
- CROSSFIRE TORCH
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VACUUM PUMPING: The degree of vacuum necessary for tubes is such that a vacuum SYSTEM is required.
- TWO STAGE ROTARY VANE MECHANICAL PUMP
- 3 STAGE AIR COOLED DIFFUSION PUMP
- HIGH VACUUM VALVE TO FIT INLET OF DIFFUSION PUMP
- HIGH VACUUM VALVE TO FIT OUTLET OF DIFFUSION PUMP
The two types of pumps are manditory.
The inlet valve lets you open the system to air without shutting off the diffusion pump. This is not strictly necessary but saves considerable time when changing out tubes. The outlet valve is necessary to isolate the diffusion pump while roughing down the vacuum tube from atmospheric pressure. Without this valve, you would have to cool off the diffusion pump while you did the roughdown. Very time consuming. The vacuum system is described in detail in the section MAKING THE VACUUM in this website.
PINCHER WELDER: The main way electrodes in the tube are interconnected is via resistance welding. A hand held pincher with electrical contacts is used to clamp the two parts to be welded. A brief burst of electric current is passed to make the weld. This is an essential piece of equipment and will be necessary to have.
GLASS LATHE: Of all the equipment used in tube making, the torches and glass lathe are the most used. However, it is possible to get by without a glass lathe. It will take a LOT more experience at glassblowing technique. You can make up fixtures of wood and sheet metal to handle a lot of the setups, but it will be quite difficult to hold the parts of the tube in exact relation, sometimes as close as 1/2 millimeter spacing, while doing the seals. Unfortunately, the glass lathe is the most expensive tool in glasswork. If you plan to make a continuing practice of tubemaking, you should plan to have a glass lathe. If you are only going to make a few tubes and go on to something else, simply make tubes that can be made without a glass lathe. Several are described in detail on this site.
BAKEOUT OVEN: When pumping the tube to develop the vacuum, the air trapped in the glass and elements must be driven completely out to keep it from seeping out over time after the tube has been sealed off, thus ruining the vacuum. To drive the air out the tube is heated to 1000 deg. F while the tube is being pumped. This requires a small oven that can be placed around the tube while it is on the vacuum system. If you are making tubes that are expected to last longer than a day or two after being sealed off, the bakeout is absolutely necessary.
GETTER FLASHER: The getter is absolutely necessary if you expect the tube to remain good for longer than a few weeks. The getter is a small element containing a reactive metal such as barium. The getter metal is heated to evaporate it onto the inside surface of the tube envelope. This must be done while the tube is under high vacuum, so the heating must be done through the glass. This is done with an induction heater connected to a suitable coil that is held over the tube adjacent to the getter element. The getter flasher is available for around $400 U.S. or you can build one with parts from ebay for much less.
TUBE TESTER: This is not your standard tube tester like is used to test TV tubes. This is a metered power supply that allows you to adjust the various voltages applied to the new tube while watching the results on meters. This tester is not available commercially and would have to be homebuilt. You could get by without the tube tester by using portable bench power supplies and a V.O.M. to read the tube current. This would be quite inconvenient.
VARIOUS HAND TOOLS: There are various hand tools that are used in the working of glass, such as carbon prods, carbon flats, pinchers, wire holders, etc. These are necessary and very easy to make yourself. All the tools you would need to do the tube glasswork would be easily made up for under a hundred dollars, so these tools are not a problem to get.
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