Bar none, the cheapest route to a hobbed bolt you’ll ever find.
The secret: Use a metric bolt, and find an SAE nut. Crossthread the nut hand_tight, then push the bearings up against the head and nut, support in vice, gently hob using a tap.
I used a 1/4-28 tap as it was what I had on hand. Had to hob two bolts as one was too deep, and the second one had to be tapped out of the bearing as the…hobs? were slightly wider than the diameter of the bolt.
I used a Mill, but there’s no real lateral loading, I don’t see why you couldn’t use a drill press to do the same.
Heck if I know. I suspect it ‘hops’ slightly when it gets to the point where they don’t line up. I found, when starting slowly, that I could turn it one direction with my fingers to cut a slight ridge, then reversed the direction and it started auto-feeding.
Because I had the SAE nut and only one Metric one. As far as it being an old trick, yeah, I’m really not surprised…but sometimes old tricks need to be rediscovered…I’ve seen so many hobbing tools on thingiverse, and I was kinda mad at myself last night…I’ve got a machine shop and no hobbed bolt. I had no desire to start throwing chips to make a hobbing tool, and had less desire to spend $6 and wait a week on an ebay purchase.
@Joe_Spanier Just place a wide file flat against the side of the bolt and file the burrs off without touching the grooved section, the bearings will come off fine.
I suspect it ‘hops’ slightly when it gets to the point where they don’t line up. I found, when starting slowly, that I could turn it one direction with my fingers to cut a slight ridge, then reversed the direction and it started auto-feeding.