Parker Stafford's Automatic Glassblowing Bench
* Updated February 5, 2001 *
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Parker Stafford generously provided the information and photos on this page to share with everyone. I provided the photo captions, some text editing, and laid out the page. Parker provided a lot more text about building this device which I will add as time allows, but the photos pretty much speak for themselves. I work without an assistant about ninety-nine percent of the time, and I think Parker's device looks like a very handy addition to the one-person studio. In fact, I plan to build a slightly modified version myself.- Brad
Parker's automatic glassblowing bench.
Here is Parker's automatic blowing bench with a pipe in place. Note the air gun used as a knee operated air valve mounted on the bench below the pipe head. Note also the regulator mounted below the left bench rail to control the maximum air pressure.
The beauty of this device is that it serves two functions - it is both a threading device as well as a means of using a blowhose at the bench without tripping over your hose every time you turn around. This removes the shackles of the blow hose extension, or having to rely on a person to track the pipe on the rails giving just the right puff of air into the piece. As much as I'd like to take credit for this idea, this design is based on something I saw Bill Boysen put together while I was at Southern Illinois University at Carbondale. He in turn had seen something like it elsewhere, and we have all made our own versions. Fenton uses metered blasts of air from a hose in filling pieces they blow into molds, for example. I was able to use what Bill had on one of the benches at school, took parts that I liked, such as the control of the air by the leg on the right hand rail, and the position of the regulator on the left rail, and made improvements in other areas. This design lends itself to various modifications. One alteration to this concept allows a person who does not have a compressor, for example, to simply have a blow hose easily available at the bench, with air supplied by the person working at the bench. In fact, when building the system, I considered this because I didn't have a compressor at the time. In the end, I realized that I really needed the compressor for a wide range of uses.
A close-up shot of Parker's furry leg and the air gun he adapted for use as a knee operated air valve.
One design change has to do with the knee valve. I am in the process of putting together a piece of metal that has a shallow bowl shape that will fit my knee, and will allow people with shorter legs (like my assistant) to use the device using the knee. This valve could be mounted anywhere really, even as a floor pedal. The beauty of this design is that you can take the basic idea and run with it, making changes or using materials different from what I have either for economy or preference. Personally I have enjoyed being able to adjust pressure for ornaments one day and large vase forms the next.
The end that the air gets delivered through with air delivery bearing mounted in appropriate sized pipe. One roller bearing installed and the other loose on the bench rail. Note the spacing washer between bearing and rail.
There were a number of possible design options for mounting the air delivery bearing (the one the mouthpiece of the pipe sticks into) but I chose something that has worked very well for me. First I took the bearing and roughed up the outer surface with a grinder, creating in effect small grooves to aid in allowing the epoxy to grab in the next step. I laid the bearing down on the bench with some wax paper underneath, put a two-part epoxy on the inside wall of the pipe/housing and then set the pipe over the bearing and positioned the bearing so it was centered. I took more epoxy and filled the crevice between the bearing and the pipe just to make doubly sure I was getting a good seal. I then welded a 1/4" female fitting on the end of this pipe (being very careful not to heat the bearing up too much in the process), welded the housing to a support, and hooked up the air hose to the end. You could do this welding before putting the bearing in, but you will need to have a way to make sure that you get good penetration of the epoxy and a positive seal if the device is going to work well and not leak. If the housing is enclosed on one end it makes it harder to get epoxy into the small gap that exists. It is my experience that you need to be able to lay the pipe and bearing down to allow the epoxy to gather and pool, thus making a positive air seal. You could also have a housing machined so that you have to tap the bearing into place after doing the welding. My guess is that you would still need something to make a perfect seal, so epoxy or something similar would be used to fill in any gaps to make it truly air tight.
View of air delivery bearing mount and supply hose from front right side of bench. It is very important to get everything aligned correctly. Because of this, it might be a good idea to make the mount adjustable (otherwise, different diameter pipes will ride higher or lower in the bearing).
The most important thing in all of this is alignment, for reasons that I think will become immediately obvious. The bench bearings and the air supply bearing must all be in very close alignment with one another, otherwise the pipe will simply not roll on center. The way I did this was to get my bench bearings set into place the way I liked and then I forged a piece of metal into the shape needed to get the air supply into very close alignment, welded it into place, then I set the air bearing housing onto this support or armature, put a blow pipe on the rails to check alignment (use a new or really straight pipe when you do this) and got everything lined up so that it all worked nice and smoothly with the pipe rotating.
Most of us are pretty sharp when it comes to visual stuff ( emphasis on "most"), and it should be pretty clear just how this thing is put together, with the details varying based on how the individual wants to ultimately make it happen design wise. The rollers and the air bearing are the most critical, and they all have to be in alignment. Some thought to the size of the mouth pieces of your pipes has to be made when getting bearings for the mouth piece part. The bearings near the hot end should not have plastic or rubber seals. Bearings with metal seals cost more, but then they can also take the heat. Three going on four years and no hint of trouble.
Beyond that, I think everything else is pretty basic.- Parker Stafford
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