Project: Fidget Spinner
Saturday, May 6 2017
My eldest grandson will soon be 11. Seems one of the in things these days are fidget spinners. I can make that. Maybe not as fancy as store bought, but I’m sure he’ll get at least 5 minutes of enjoyment out of the toy.
I cut out a 2" x 2" (plus) section from some 3/8" steel. I’m going for a 50 mm diameter with a skate bearing (22 mm OD) in the center. That leaves room for 10 8 mm holes to even things out.
First try: I spot drilled the hole pattern using tables from Machinery’s Handbook adjusted for diameter. It looked OK so I drilled the holes. I do not have a DRO on my micro mill, only the dials. Somewhere along the line I messed up turning the dials. When I mounted the part to a mandrel I made using the center hole and put the mandrel in the lathe it became obvious that my center hole was no where near the center of the pattern.
Second try: Cut another piece of 2" x 2" (plus) steel. Mark and drill the center. Mount to the mandrel and put it on the lathe. Turn down to the desired diameter. Move the piece to the 3 jaw chuck, face both sides, and bore the center to the desired size. Chamfer all edges. Now move the piece to the mill.
I used an edge finder on the internal 22 mm hole to determine the center and then used the tables from the handbook adjusted for diameter. The first 6 holes were fine but I could see when I went to spot drill the 7th hole that I’d goofed. No problem. I was able to go back to my center and re-position the mill table. Apparently I’d miss counted a rotation of the crank and was off by 0.050". It was very easy to see I was off on the circular part before I messed up.
After drilling and deburring all 10 holes I used a counter-sink in a hand drill to slightly chamfer the holes. Some cold blueing was applied to give it darker look and hopefully inhibit corrosion. Lastly the bearing was inserted with a few drops of loctite super glue just to make sure is stays.
I may be able to salvage my first try. The hole pattern is not perfect, but OK for a childs toy. I’ll try to center the piece on the hole pattern in my 4-jaw chuck and bore a hole at center. I’ll make another mandrel to fit the hole once it is round. Then I can turn the outer edge. I hope.
Sunday, May 7 2017
It looks like I can save my first try. Unless I screw something else up.
I put the piece in a 4-jaw chuck and aligned the pointer of my surface gauge with the outside edge of one of the holes. I went back and forth adjusting the jaws of the chuck and the pointer until the outer edge of all holes aligned with the pointer as I spun the chuck.
Once that was done I ignored the existing off center hole and bored a new hole to the desired 22 mm dimension for the bearing. It was an interrupted cut until the new hole subsumed the original hole.
I put my collet chuck on the lathe and mounted my original mandrel inverted. I’ll turn down the larger diameter to match the 22 mm I bored in the spinner. Then I can mount the spinner and turn it down to the desired size. I’ll probably saw off some of the larger points, first. Much faster that way.
Monday, May 8 2017
I cut off some of the corners and turned the mandrel down to size for a tight fit on the spinner. I wound up holding the mandrel in the 3-jaw chuck instead of the collet chuck. I had plenty of material to grab. I was turning down less than 3/8" to the 22 mm diameter needed to hold the part.
Done. It will be the back-up toy, stored for whenever the original is lost. I’m assuming that 11 year old boys still lose things. I did when at that age. Alas, I still do. With my luck I’ll forget where I put this back-up if the original is ever lost.