Hi Mike, I'm happy to answer questions and clarify things. Just glad someone is interested enough to ask.
This was my first turning on the lathe once I got it running. I remember feeling like I was running by the seat of my pants, basically trying to copy what some others have done and posted about here. Nothing was aligned and I had pretty crude cutting tools at that time, so the finish quality was pretty so so.
The spider I turned from a 3-inch long piece of 1018 steel tubing, 2-1/2" in diameter with 1/2" wall thickness. This is what I started with.
After facing off one end, I bored out the ID to give a close fit to the section of spindle sticking out the left side of the headstock. I don't remember now the precise dimension, but I ended up about 0.001 to 0.002" oversized on the ID. I bored just deep enough to create a flat shoulder to rest against the end of the spindle - giving it a registration seat against the spindle end. Looks like this:
It ended up with a nice slip fit. I then turned down the OD just enough to provide clearance with the hole in the gear cover casting that mounts over the change gears and pulley/belt drive, then turned the part around, mounted it on the lathe in a 4-jaw chuck, centered it and faced off and cleaned up the ID and OD from the opposite end.
To secure the spider sleeve to the spindle, I drilled and tapped for M6 brass tipped set screws 120 degrees apart on the mill, then did another row also 120 degrees apart but clocked 60-degrees out of phase with the first set, and about 1/2" further out on the spider. I wasn't sure if 3 set screws were enough, or if I'd need an outboard set to keep it aligned both radially and axially - as you can see, I'm paranoid and inclined to belt and suspenders wherever possible. I also machined out pockets for the cylindrical magnets for the Hall Effect sensor on the MachTach at that end. Here's a photo that shows that detail, but I never installed the second set of three set screws - didn't need them:
At the outboard end of the spider sleeve, I decided to employ 4 screws 90-degrees apart to dial in whatever part the spider was keeping aligned. I figured four screws would be easier to adjust the part to centerline than three (and I was right). I first milled a flat spot about 5/8" diameter then drilled and tapped for 1/4-28 alignment screws. The screws shown are brass tipped steel (McMaster 91381A359) and I used Stainless Steel Knurled-Head Thumb Nuts (McMaster 91833A107) to secure the adjustment screws. This is how the adjustment screws look from the end.
I have a second set of longer screws for smaller diameter work with longer reach. I made those from socket-head cap screws, drilled the ends to receive tiny brass rod inserts secured with Loctite.
And finally, I used a 10ths indicator to mount the spider and align it radially and axially so it has no wobble and doesn't create any shimmy or weird vibrations at high speed.
Hope this helps.
