Rollie Bowns of the NorCal Chapter (Sacramento, CA) sent me the following idea I thought was interesting. Reprinted with permission!
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Below is a picture of the steel extension I made to replace a plywood prototype. The point of it is to have extra length on the rare occasion when I need it. One of my sons says that I make these things more for the fun of making them that any real use I will get out of it. There is some truth to that. Anyway, it cost me $6.33 for the metal and bolts. That does not include the welding rods I used. Pretty cheap compared to some other alternatives.
I also considered putting an additional factory extension on the head stock end. However, in addition to the cost of the extension I have two problems. One is that there are no holes for the bolts on the head stock end of my lathe and drilling the holes by hand would not be easy (exact placement being the major problem). The other is that the factory extensions have ways that are 50 thousandths of an inch thicker than the ways of my lathe (an original 3520.) They changed the thickness of the ways when Jet took over. I bought my factory extension on sale from Southern Tool and then had to spend $100 to get it milled to the right thickness. There went the savings!
I have attached two pictures. One is of the new steel extension. The other is of the plate I made to lower the factory extension and the banjo and tool rest I made for it. The factory extension is set at the lowest of four settings and at that setting it gives a turning capacity of 44 1/2 inches in diameter. The faceplate on the lathe is 31" in diameter. (I used that a couple of years ago to make a project for the State Fair.)
As to the alignment, that was the difficult part of the construction. The parts have to be aligned and welded and drilled quite precisely. If that is done, then you simply bolt it together and it is right. Also, as you point out, on a turning that is five or six feet long, a slight misalignment of the headstock/tailstock is not going to matter.
As to the long spindle turning there are several ways to solve the problem of the space over the extension. One is to reverse the turning (swap ends). Another is to use a long tool rest and position the banjo at an angle. Here, one must use light cuts so as to not put too much strain on the banjo which is hanging out quite far. Turn what you can with the banjo on the lathe, then move it to the factory extension and turn the rest. Another method would be to slide the whole thing (headstock, turning, and tailstock as far as you can to the left (so as much of the turning as possible is over the lathe bed) and turn what you can, then slide all of it as far as you can to the right, move the banjo and tool rest to the factory extension and turn the rest. The last possibility is to buy another banjo and build a tool rest that spans the extension I made and rests in the two banjos.
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Below is a picture of the steel extension I made to replace a plywood prototype. The point of it is to have extra length on the rare occasion when I need it. One of my sons says that I make these things more for the fun of making them that any real use I will get out of it. There is some truth to that. Anyway, it cost me $6.33 for the metal and bolts. That does not include the welding rods I used. Pretty cheap compared to some other alternatives.
I also considered putting an additional factory extension on the head stock end. However, in addition to the cost of the extension I have two problems. One is that there are no holes for the bolts on the head stock end of my lathe and drilling the holes by hand would not be easy (exact placement being the major problem). The other is that the factory extensions have ways that are 50 thousandths of an inch thicker than the ways of my lathe (an original 3520.) They changed the thickness of the ways when Jet took over. I bought my factory extension on sale from Southern Tool and then had to spend $100 to get it milled to the right thickness. There went the savings!
I have attached two pictures. One is of the new steel extension. The other is of the plate I made to lower the factory extension and the banjo and tool rest I made for it. The factory extension is set at the lowest of four settings and at that setting it gives a turning capacity of 44 1/2 inches in diameter. The faceplate on the lathe is 31" in diameter. (I used that a couple of years ago to make a project for the State Fair.)
As to the alignment, that was the difficult part of the construction. The parts have to be aligned and welded and drilled quite precisely. If that is done, then you simply bolt it together and it is right. Also, as you point out, on a turning that is five or six feet long, a slight misalignment of the headstock/tailstock is not going to matter.
As to the long spindle turning there are several ways to solve the problem of the space over the extension. One is to reverse the turning (swap ends). Another is to use a long tool rest and position the banjo at an angle. Here, one must use light cuts so as to not put too much strain on the banjo which is hanging out quite far. Turn what you can with the banjo on the lathe, then move it to the factory extension and turn the rest. Another method would be to slide the whole thing (headstock, turning, and tailstock as far as you can to the left (so as much of the turning as possible is over the lathe bed) and turn what you can, then slide all of it as far as you can to the right, move the banjo and tool rest to the factory extension and turn the rest. The last possibility is to buy another banjo and build a tool rest that spans the extension I made and rests in the two banjos.
