Milling a helix
Posted: Mon Jun 04, 2018 1:16 am
I have a multitude of projects I'm trying to address, so I can get my shop fully operational. It's a daunting task, with some things necessary before others, so I don't paint myself in to a corner. Getting my muller operational is one of those things, which must be rebuilt and placed before I set the two furnaces for my induction melting system. I don't have excessive space, so things will be snug, with the two furnaces precluding access to the muller with my fork lift.
That said, I dismantled the muller for cleaning and rebuilding some time ago. I've made new axles for the rollers, which I made 1/16" oversized, which then allowed me to rebore the original bronze bushings for a proper fit. The wheels mount on an overhead arm, which was honed to restore the bores, and new shafts made. The mounting end is square, and required re-machining, as the muller had been somewhat abused and neglected, with the arms operated without the mounting bolt firmly tightened, resulting in worn attaching points. It is all like new now, and should work well for a long time to come.
I was feeling pretty good about the restoration project, but when I got down to the transmission, which is a simple worm/gear assembly, I found that water had entered the oil, resulting in a badly pitted worm, but only where it was submerged in the oil, which, now, was rather viscous.
I contacted Simpson, the maker of the muller, and discovered the machine was built in 1947, and sold to the University of Utah. That all made sense, for I knew it was old, and it was purchased by me from their surplus sales about 25 years ago. Like the induction furnace, it was placed in storage until the day came when I could attempt to make it operational.
Simpson was wonderful, once I reached the CEO. The parts department didn't address my inquiry, so I chanced sending a message to him to see if I could learn more. It was he who told me about the original buyer, and when it was built, and he answered the question about the lack of response from their parts department. The company had scrapped all the files prior to 1950, thus they were not able to help.
That left me with the need for a new worm, which is integral with the shaft, and is a bastard. There is nothing on the market that could substitute, so I pondered the idea of regrinding the worm, which I could do with a gearing setup, using my cutter grinder, if only the head could be tilted to parallel the helix angle. It can not.
I started thinking about making a new one, but the worm is akin to a 29° Acme thread, with a lead of 5/8" (the screw advances 5/8" per revolution). As my Graziano is way too small to accommodate that kind of pitch, I started thinking about cutting the worm on my Bridgeport. A simple gearing setup would allow the generation of the helix, with the added advantage of not requiring a form cutter, as the head can be tilted to 14°30' so each face can be machined individually. Convinced I could use Stressproof for material, eliminating the heat treat, I decided to build the required attachment.
When an old buddy closed his shop a few years ago, I was gifted his supply of material. Included was a nice piece of 3/4" aluminum tooling plate, about 23" square, although it had been used as a base plate for what was likely a CNC. No matter, it would still serve the purpose, and the price was right. I just have to live with the odd hole that makes no sense, and the slots that were already milled in the plate. Most of them are hidden by making that face the bottom.
I began the build by inspecting the left hand side of the table, where I had, long ago, removed the handle. I don't operate my mill from that postion, and I didn't like it twirling when I was using power feed. It didn't take but a few seconds to realize that I could make an adapter that fit where the handle did, and it would be driven by the same key slot that drove the handle. I went to my collection of gears, of which I have about 150. I found I had several 54 tooth gears, which would work perfectly for the application at hand. I made the adapter, then I started with the aluminum tooling plate. I wanted to be able to place the power takeoff on the machine without hassle, so I made a pair of pins that locate the adapter plate square, with the left side pin also acting as a stop, so the plate is properly oriented with the gear on the end. I then made the base plate and vertical plate, determining locations of slots as I progressed. None of this was drawn up---it was built according to what appeared to work as I'd place pieces on the plate.
In order for the power takeoff to be reversed, I cut a slot that would allow the addition of a fifth gear. It is unused, as the device appears to be operating in the proper direction for the given application.
In order for a telescoping drive to be used (one has no idea how long the connecting shaft must be for any given setup), I used a socket that has a U joint as part of its design. The socket is 3/8" drive, and will accommodate 5/16" square material, which I will use as part of the telescoping drive shaft. I also happened to have a 5/16" square holed sleeve, which will be silver soldered inside a piece of 3/8" pipe.
I was fortunate to find a pair of the sockets, each different, and each perfectly suited to the application, in the toolbox I acquired when I married my wife those many years ago. Her first husband, who was just a lad of 23, was killed in a collision while on a weekend drill in the Utah Air Guard. He had worked as a diesel mechanic, so he had some very nice tools.
In order for the socket to be mounted, I had to drill and tap for a set screw in each half. I figured sockets were heat treated, which they are, but the one thing I didn't count on was that they might be nitrided, but that turns out to be the case. I tried dimpling the socket with a center drill, only to see the tip of the center drill quickly be rubbed away. Not to be deterred, I figured if I could get through the exterior, I could probably drill and tap with little trouble, and that proved to be the case. I selected a couple scrap pieces of round carbide, from which I quickly ground a couple spade drills. Size was not important, all I needed to do was get through the skin with a larger diameter than the tap (10-32) I'd use. I was amazed to see the carbide walk right through the skin, in spite of my careless grinding, which was offhand with no particular attention paid to center or uniformity.
Long story short, I now have that portion of the setup operational. I still have to make a base plate for the holding device, which will be an unmatched tailstock and my Hardinge index head, as well as a second gear plate, which will allow power to be transferred to the worm I intend to mill. I've included the worm/shaft in both pictures, to give you an idea of what I'm talking about.
I'll try to post on my progress at some future date, maybe even include a picture of the entire setup, in use, but for right now I thought you guys might like seeing how a gear setup can be built that allows for creating helixes on a milling machine.
H
That said, I dismantled the muller for cleaning and rebuilding some time ago. I've made new axles for the rollers, which I made 1/16" oversized, which then allowed me to rebore the original bronze bushings for a proper fit. The wheels mount on an overhead arm, which was honed to restore the bores, and new shafts made. The mounting end is square, and required re-machining, as the muller had been somewhat abused and neglected, with the arms operated without the mounting bolt firmly tightened, resulting in worn attaching points. It is all like new now, and should work well for a long time to come.
I was feeling pretty good about the restoration project, but when I got down to the transmission, which is a simple worm/gear assembly, I found that water had entered the oil, resulting in a badly pitted worm, but only where it was submerged in the oil, which, now, was rather viscous.
I contacted Simpson, the maker of the muller, and discovered the machine was built in 1947, and sold to the University of Utah. That all made sense, for I knew it was old, and it was purchased by me from their surplus sales about 25 years ago. Like the induction furnace, it was placed in storage until the day came when I could attempt to make it operational.
Simpson was wonderful, once I reached the CEO. The parts department didn't address my inquiry, so I chanced sending a message to him to see if I could learn more. It was he who told me about the original buyer, and when it was built, and he answered the question about the lack of response from their parts department. The company had scrapped all the files prior to 1950, thus they were not able to help.
That left me with the need for a new worm, which is integral with the shaft, and is a bastard. There is nothing on the market that could substitute, so I pondered the idea of regrinding the worm, which I could do with a gearing setup, using my cutter grinder, if only the head could be tilted to parallel the helix angle. It can not.
I started thinking about making a new one, but the worm is akin to a 29° Acme thread, with a lead of 5/8" (the screw advances 5/8" per revolution). As my Graziano is way too small to accommodate that kind of pitch, I started thinking about cutting the worm on my Bridgeport. A simple gearing setup would allow the generation of the helix, with the added advantage of not requiring a form cutter, as the head can be tilted to 14°30' so each face can be machined individually. Convinced I could use Stressproof for material, eliminating the heat treat, I decided to build the required attachment.
When an old buddy closed his shop a few years ago, I was gifted his supply of material. Included was a nice piece of 3/4" aluminum tooling plate, about 23" square, although it had been used as a base plate for what was likely a CNC. No matter, it would still serve the purpose, and the price was right. I just have to live with the odd hole that makes no sense, and the slots that were already milled in the plate. Most of them are hidden by making that face the bottom.
I began the build by inspecting the left hand side of the table, where I had, long ago, removed the handle. I don't operate my mill from that postion, and I didn't like it twirling when I was using power feed. It didn't take but a few seconds to realize that I could make an adapter that fit where the handle did, and it would be driven by the same key slot that drove the handle. I went to my collection of gears, of which I have about 150. I found I had several 54 tooth gears, which would work perfectly for the application at hand. I made the adapter, then I started with the aluminum tooling plate. I wanted to be able to place the power takeoff on the machine without hassle, so I made a pair of pins that locate the adapter plate square, with the left side pin also acting as a stop, so the plate is properly oriented with the gear on the end. I then made the base plate and vertical plate, determining locations of slots as I progressed. None of this was drawn up---it was built according to what appeared to work as I'd place pieces on the plate.
In order for the power takeoff to be reversed, I cut a slot that would allow the addition of a fifth gear. It is unused, as the device appears to be operating in the proper direction for the given application.
In order for a telescoping drive to be used (one has no idea how long the connecting shaft must be for any given setup), I used a socket that has a U joint as part of its design. The socket is 3/8" drive, and will accommodate 5/16" square material, which I will use as part of the telescoping drive shaft. I also happened to have a 5/16" square holed sleeve, which will be silver soldered inside a piece of 3/8" pipe.
I was fortunate to find a pair of the sockets, each different, and each perfectly suited to the application, in the toolbox I acquired when I married my wife those many years ago. Her first husband, who was just a lad of 23, was killed in a collision while on a weekend drill in the Utah Air Guard. He had worked as a diesel mechanic, so he had some very nice tools.
In order for the socket to be mounted, I had to drill and tap for a set screw in each half. I figured sockets were heat treated, which they are, but the one thing I didn't count on was that they might be nitrided, but that turns out to be the case. I tried dimpling the socket with a center drill, only to see the tip of the center drill quickly be rubbed away. Not to be deterred, I figured if I could get through the exterior, I could probably drill and tap with little trouble, and that proved to be the case. I selected a couple scrap pieces of round carbide, from which I quickly ground a couple spade drills. Size was not important, all I needed to do was get through the skin with a larger diameter than the tap (10-32) I'd use. I was amazed to see the carbide walk right through the skin, in spite of my careless grinding, which was offhand with no particular attention paid to center or uniformity.
Long story short, I now have that portion of the setup operational. I still have to make a base plate for the holding device, which will be an unmatched tailstock and my Hardinge index head, as well as a second gear plate, which will allow power to be transferred to the worm I intend to mill. I've included the worm/shaft in both pictures, to give you an idea of what I'm talking about.
I'll try to post on my progress at some future date, maybe even include a picture of the entire setup, in use, but for right now I thought you guys might like seeing how a gear setup can be built that allows for creating helixes on a milling machine.
H