Archive for March 7th, 2016
Replacing the hex nut traps with knurled insert cylinders slims the ends of the socket:
Making the raised part of the socket fit the 25 mm ID of a hard drive platter swells the midsection of the socket
, but the platter won’t need any machining or punching:
The octal and duodecar sockets will require a punch to open up the platter hole and all sockets require two drilled clearance holes for the screws. Given that I’ll eventually do this on the Sherline, maybe milling the hole for the bigger tubes will be faster & easier than manually punching them.
I moved the screw centers to 35 mm (from the historically accurate 28 mm) to accommodate the larger center, not that anybody will ever notice, and enlarged the central hole to 7.5 mm (from 5.0 mm) to let more light into the tube base.
The support structures inside the (now much smaller) knurled insert cylinders might not be strictly necessary, but I left them in place to see how well they built. Which was perfectly, as it turns out, and they popped out with a slight push:
They’re just the cutest little things (those are 0.100 inch grid squares in the background):
Anyhow, the knurled inserts pressed into their holes with a slight shove:
The chuck jaws were loose on the screw cutoff stud and stopped at the surface, putting the knurled inserts perfectly flush with the socket:
The surface looks very slightly distorted around the inserts, although it’s still smooth to the touch, and I think the PETG will slowly relax around the knurls. Even without heat or epoxy, they’re now impossible to pull out with any force I’m willing to apply to the screws threaded into them. Given that the platter screws will (be trying to) pull the inserts through the socket, I think a dry install will suffice for my simple needs.
Match-mark, drill #27 6-32 clearance holes, and the screws drop right in:
Those stainless steel pan-head 6-32 screws seem a bit large in comparison with the socket. Perhaps I should use 4-40 screws, even though they’re not, ahem, historically accurate.
The tube pin holes get hand-reamed with a #53 drill = 1.5 mm. That’s a bit over the nominal 1.1 mm pin diameter, but seems to provide both easy insertion and firm retention. For permanent installation, an adhesive would be in order.
Buff off the fingerprints, stick the tube in place, and it looks pretty good:
Yeah, those screws are too big. Maybe a brace of black M3 socket head screws would look better, despite a complete lack of historicity.
Now to wire it up and ponder how to build a base.
The OpenSCAD source code as a GitHub Gist: