Universal Joint

[Brian Rupnow]

1144 and 12L14 are both very nice steels to machine. My machine doesn't mind the 1045 at all. I haven't got to the mill yet with the A36. Tennessee--there won't be any bearings in these universals. I am going to make the spider out of bronze.  These are going to be "low mileage" universals. They will only see duty on my many different mechanisms that I drive with my engines.

[Brian Rupnow]

Here you can see an "in process" of cutting the centers out of the universal joint ends. I futzed around a bit just figuring out how I was going to do this, then drilled a 3/16" hole at each corner of what would be opened up and then just "chain plunged" with a 3/16" endmill all around between the holes, running at about 750 rpm taking 0.020" steps between full depth plunges. These are actually turning out too nice to free-hand the end radius. I may have to machine up a couple of filing buttons out of some 01 and harden it so I can make decent looking ends on the pieces.

[Brian Rupnow]

Well---that was a bummer!!! Turned up a nice filing button, heated it, quenched it---then tried it with a file and it cuts like butter. Some donkey put a stick of cold rolled in the drill rod rack. And since I'm the only person with access, well----However, I did find a piece of drill rod the right diameter after the fact, so that will be tomorrow mornings job.

[crueby]

Well---that was a bummer!!! Turned up a nice filing button, heated it, quenched it---then tried it with a file and it cuts like butter. Some donkey put a stick of cold rolled in the drill rod rack. And since I'm the only person with access, well----However, I did find a piece of drill rod the right diameter after the fact, so that will be tomorrow mornings job.

I'd blame the shop gnomes. Yeah, thats it, the gnomes...

[Brian Rupnow]

For anyone out there who doesn't fully grock the concept of "filing buttons" it is a rather neat trick. I wanted the radius on the tips of the universal where the 3/16" hole goes thru the arms to be nice and concentric to the hole. You could accomplish this with the proper set-up in a rotary table. You could (if you are very steady and keen of eye), do it freehand on a big belt sander. That is the way I do it most of the time on bigger parts. However, this trick is neat, I learned it of British steam engine web-sites. If you have a piece of drill rod the diameter of the finished end you want to put the radius on, then turn down an area small enough to fit thru the hole, then harden the drill rod by torch and quench method. I didn't bother cutting my drill rod down to a short length to make a "button"---I left it full length on the end of the rod. It doesn't matter. Put the part to be filed in your vice, insert the hardened drill rod, then start filing on the sharp corners of your piece. The file will only cut material until it gets down to the surface of the hardened drill rod, and won't go any farther, because the drill rod is now harder than the devils horn, and the file won't cut it. this leaves a very nice radius on the part you were filing.

[Brian Rupnow]

Now I'm at a juncture---I was going to finish all the ends first, then do the center spiders.--but--This looks so exciting I can't wait. I have to make the spider now and finish this first universal joint.

[mklotz]

Hey Brian, here's something that can employ your universals

https://s3-us-west-1.amazonaws.com/hmt-forum/gears_with_direction_change.gif

[Brian Rupnow]

Yes Marv. I've seen that before. That is very close to being a set of mangle gears. Be a bit tough to build in metal though, I think.

[Brian Rupnow]

The spider is finished, and it turned out really good. There was a nifty trick used in machining that. The material is 3/8" thick. I cut out the profile on my bandsaw, leaving just enough material for cleanup. I cleaned up the 4 cut sides on my beltsander, and cleaned up the 4 notches in the corners of what started out as a rectangular piece of bronze with a file. Set it up in the mill vice and reamed one 3/16" diameter hole thru, then turned it 90 degrees and put the second 3/16" hole thru. Now comes the trick part. 3/16" is 0.188". The outer diameter of a #10 bolt is 0.190" in diameter. A bolt that size will "self thread" thru brass or bronze, cutting a very shallow thread. I tapped a #10-24 thread in the end of a piece of round 5/16" diameter cold rolled while it was set up in the lathe 3 jaw chuck. The socket head bolt goes thru the bronze part and screw into the end of the 5/16" diameter cold rolled steel rod. Then, using a 3/32" cut off tool, and the o.d. of the steel rod as a reference diameter (that is the diameter of the bosses on the spider) I took cuts in .030" increments from the face of the spider closest to the chuck, until the newly cut boss reached the length I desired. Did that 4 times. ran the 3/16 reamer thru each hole once more, and it was finished.

[Brian Rupnow]

And there it is finished, in one of it's potential new homes. I coat the inside of the bronze spider with good quality grease, tap the pre-cut to length pieces of 3/16" cold rolled shaft almost home (one is a single piece which goes all the way thru everything, two of the pieces are shorter and just butt up against the long one at the center of the spider), and coat the last 1/16" with 638 Loctite before tapping them all down flush with the outside of the universal joint body.

[Perry]

Helo Brian, in one of the photos above I see you are using what looks like an ordinary drill chuck to hold the endmill. Do you have good experience with that combo?
Regards
Perry

[Brian Rupnow]

Perry--I do. That is an old battle that I have fought many times. Would I do it with a full size Bridgeport that was being used on a production basis?--No. Would I do it side milling steel under high loads with big endmills?--again, no. With smaller endmills and working with aluminum I do it all the time. If milling steel with anything bigger than a 3/8" endmill I use an endmill holder. Remember, I work almost exclusively in the world of model engineering. On a small scale you can get away with a lot of things that you couldn't get away with doing on big full size machines in a production environment.

[wagnmkr]

Congrats Brian ... that looks the part and I am sure it will be quite strong as well. A bit large for what I need, but I am going to re-scale it and have a go.

Do you have any snow up there yet? I need to get up to the metal toy store one day soon.

Tom

[Brian Rupnow]

HiTom---we've got about 2" of snow on the ground. I don't think it will stay. The weather guys are calling for rain later in the week.

[wagnmkr]

Thanks Brian ... about the same as us then. We also have the forecast for rain and freezing rain.

Tom