Kris Holm: How about some "legacy" support?

Pft. Using a cylinder hone on bearing holders? There are so many things wrong with that it’s hard to know where to start:

1: Hones are used to create a “crosshatch pattern” in cylinders for oil retention with piston rings. On worn cylinders, they are designed to resurface the ID, while removing a MINIMUM amount of material. They are not designed or used to enlarge cylinders as dramatically as 2mm (~0.08"). You would destroy the hone doing so.

  1. Bearing holders have lips. This alone eliminates the possibility of using a hone.

  2. bearing holders are split such that if they are tightened down without a bearing in them, they will not have a uniformly round ID. Thus one would have to carefully shim to size, which will leave gaps, which will further jam the hone.

  3. Cylinder hones are designed to work on bores that are significantly longer than their diameter (L=2-3xID). That isn’t even close to being the case on a bearing holder. Assuming you didn’t jam the hone in it because of 2 or 3, keeping it straight and aligned would be very challenging, if not impossible.

  4. Many unicycle frames now have aluminum bearing holders. A hone is generally meant to work on ferrous materials like steel. Aluminum would clog the abrasive, even further reducing an already painfully slow material removal rate.

  5. Assuming a machine shop has cylinder hones is like assuming a house electrician has a soldering torch for joining plumbing pipes. An automotive machine shop will have cylinder hones, but they’ll be damned if they waste them on your bearing holders, and the chances are extremely slim that they will have a hone in a size small enough for your holders. Look at the size of the average auto pistons.

This is not to say a good machine shop couldn’t enlarge your bearing holders, but if they pull out a cylinder hone, you should walk away since that means they are too incompetent to deserve your money. Also, chances are the price they would charge for the job would be enough that you’d be better off buying a new frame to start with.

Any machinist worth anything can machine you a set of bearing sleeves to make a 40mm bearing fit a 42mm holder, though. That would be a quick, easy job.

Experiance with hones

I once used a hone to bore out the cylinders on my 350 Honda to fit the next size over pistons. It was a lot of work, it took a couple hours, but it worked.

As I noted above, I recommended at brake cylinder hone, which is the correct size for bearing holders.

Sadly, as I noted in my last post, it likely won’t work with the flanges on the bearing holders. When I thought of the idea, I first envisualized the holders as looking like connecting rod ends, but then corrected myself when I remembered that the caps had flanges.

Now I would say it might be cheaper to buy a new frame, or pay extra for a Profile set up. On the bright side, they have a life guarantee.

or go to a proper machinist.

or just save a bunch of money by pulling out the hammer… …