Hi all,

I'm still playing the CAD and mouse game with designs. I'm working through vertical at the moment. First, let me describe my newly acquired spindle by saying: it's insanely big!








Some key measurements on the spindle are: ~20" (~50cm) long x 8" (~20cm) wide. The upper shaft, where the drive pulley would go is 60mm (2.3") in diameter, and though I found a possible match, options are limited for pulleys with that large of a bore. That piece at the top that looks like the top bearing, it's not. That's fixed to the rotating shaft so some kind of bearing would have to be added if I want to support that end. It's not really necessary for the spindle itself but I'm not sure about leaving it unsupported way up there.

Frankly, if it weren't for the drawbar and it's many Belleville washers, I'd machine that shaft down to mere mortal size. Thoughts of springing for a new Chinese BT40 spindle and air cylinder have crossed my mind, though shipping costs to US are ridiculous at the moment (~$550).



Here's the vertical sketch I've been working through:



I added a CAT40 holder, 1/2" (12mm) end mill and my Kurt vise to see how it would work in the real world. With Z raised all the way up, I'd have ~12" (~300mm) between the tip of the end mill and the top of the vise, and ~21" (~500mm) from the bottom of the spindle to the top of the table (no vise).

Struggling to learn basic Fusion 360, I managed to run a couple of stress tests on the vertical columns. Putting about 500 pounds (226kg) of horizontal force at the top of the columns makes them deflect a little over 0.001" (0.02mm) which is not too bad. Bracing the columns to each other will help, and so will filling them with epoxy granite. If I can figure out how to add granite in F360, I'll give that simulation a go.

Peter, how's your moving X/Z bridge design coming?

Regards,
JR