Shopsmith Mark V Single vs Double Bearing Quills

Earlier this year I started noticing some runout on the spindle of my 50 year old Shopsmith Mark V. I did some reading about my specific model and came to two conclusions:

The bearing has never been replaced and is probably worn out.

The quill in my machine is a single bearing quill.

Replacing the bearing is straightforward. Alex’s Shopsmith Repair sells them and with a few tools you can replace it yourself.

What I also learned is a bit trickier: Replacing the single bearing might solve some of the problem, but won’t solve the entire problem. Later versions of the Shopsmith shipped with double bearing quills, adding a second bearing to further support the spindle. The spindle on the single bearing quill is still supported by the drive sleeve, but there is a bit of give there, which contributes to the runout.

The rabbit hole gets a bit deeper. It turns out that Shopsmith made many different kinds of quills. Everett Davis wrote an incredible guide to all the different kinds of bearings in 2017, which includes details about the different kinds of quills. I’ve reposted that here in its entirety:

Shopsmith-Bearings-Guide-15-Oct-2017-Everett-L.-Davis Download

To be certain what kind I had, Charlie and I pulled my quill out and took it apart. Looks like a 1970s single bearing quill, which matches with my machine’s serial number.

One design flaw of the double bearing quills that Shopsmith started shipping in 1984 is that the spindle changed from a single piece of machined steel to a two-piece spindle pinned together. According to James, this is prone to bending. Also, with the two bearings being so close together and the back one being smaller, the back one wears out faster, again causing runout.

So do you choose a single bearing quill and the runout, or a double bearing quill and risk bending it when doing heavy, unbalanced turning?

At first I chose the two-piece double bearing quill since I try to balance out my work pieces as much as possible. Then Shopsmith went out of business before they shipped it to me (and closed down all customer service avenues). I eventually got my money back through a chargeback, then went hunting for alternatives.

I was going to just order new bearings, change them myself, and live with it, until I came across this video from Skip Campbell:

Skip takes the one-piece spindle single bearing quills and machines them to fit a second bearing on the back. Great idea! Best of both worlds—same-sized bearings spaced far apart on a single-piece spindle. I ordered one from him at MKC tools.

Here it is where you can see the rear bearing and the

I put it in my machine and turned a small bowl. It works like a dream. No runout, and no chatter unless I’m using my bowl gouge incorrectly. With the old one the runout caused chatter even with light cuts.

Now that Shopsmith is shut down, I’m sourcing backups of critical non-standard parts, so I’m going to reach out to Skip and see if he’ll machine my original quill to fit a second bearing so I have a replacement. I’d love for this machine to last another 50 years.