Dissected KH Hub

I have a 20" Summit uni that I got mainly to see what the KH hub is all about. I’ve taken the hub apart and posted pictures of it here:


I think the KH hub is a very good design and would like to try making a stainless steel welded flange version of it - like the other hubs I’ve made but with the KH splines. I’m convinced that a splined hub with the pinch style cranks is the best way to go for unicycles.

Steve Howard

Interesting. With all the recent talk about the profile it’s good to see the KH hubs internals.

I’ve often wondered why both the profile and the KH hubs use an axle which is fitted into a hub shell instead of simply having the hub flanges directly attached (welded?) to the axle. It seems to me that there would be a tremendous amount of weight saved in the latter design. Perhaps it is a production issue?

I much prefer the look of the SH/Profile hub over the real profile. I don’t like the look of the KH hub for the same reason. It looks like a short soup can with an axle through it.


What exactly did you do to take off the nubs on the KH cranks? Did you have to add spacers, or just take down the metal on the nub? Does it require anything special to reattach the crank arms to the hub? Is there any down side to reducing the nub? Thanks

Mr Howard I am not, but I think I can handle this question. As you can see on picture 4 a couple spaces are added on the outer end of the hub to make up for the thinner crank. I wouldn’t imagine any difference in the attaching and removal of the crank, with the exception of adding the spacers. The only downside is the greater Q factor, and I’m not even sure if that is a down side.

For better answers, just wait a bit for the big guns to answer.

Now for a few questions of my own. How hard is the nub removal surgery? Can I have some local machinist do it? If so how much would I expect it to cost?

Also, do you foresee any problems with the 6 keyways getting loose like some profiles?


Thanks for pointing that out Daniel.

You cannot weld aluminum to steel. The spindle (or axle) in the hub is hardened steel and the hub body is aluminum. The easiest way to put those two parts together is to use a pressfit and a keyway.

It would be possible to weld a steel flange on the spindle to make a hub. The DM splined hubs are made that way. But welding flanges on is tricky. You have issues with the welding weakening the hardened spindle and issues with the flanges deforming when the hub is re heat treated. The welding solution is not something you would do for a mass produced hub because it would be too much work.

Another problem with steel flanges is that they are not as spoke friendly. The spoke holes in aluminum flanges deform around the spoke shoulder and make a nice smooth comfortable spot for the spoke shoulder to rest. The spoke holes in steel flanges do not deform and put extra stress on the spoke shoulders which makes it more likely for the spoke to fail right at the shoulder. As a result, you can tension up a wheel with aluminum flanges higher than you can a wheel with steel flanges. My local wheel builder could not tension up the spokes as tightly in my DM wheel as my Profile wheel.

Aluminum hub bodies are very common on bicycles. They are standard parts that manufacturers know how to make. It allows the manufactures to make a unicycle hub out of existing parts.

Take an existing aluminum hub body
drill a hole in the hub body
machine a keyway in the hub body
take an existing splined spindle
add a key to it
press the spindle into the hub

and presto, you’ve got a unicycle hub. And that’s exactly what Profile did.

Right now that’s the easiest way to make a strong splined unicycle hub.

The KH hub evolved a little beyond the Profile design by using a better keyway design. With the multiple keyways the KH shouldn’t develop slop in the keyway like the Profile hub can (see this thread: Loose Profile keyway).

Check out these pictures:


The two possible problems with removing the crank protrusions are that the length of the splines is reduced by about 1/4" and the distance between the pedals is increased by 1/2" (1/4" per side).

It’s pretty easy on a Bridgeport type milling machine and any machinist should be able to do it. It will take about 1 hour so, depending on shop rates, will cost $40 - $50. You’ll also need spacers to take up what was removed from the cranks. I bought 1/8" thick spacers from McMaster Carr but I made stainless steel spacers for Tommy when I did his.

No - I would be surprised if the KH spincle would ever get loose in the hub with that six keyway set-up.

It’s pretty obvious that the aluminum hub on the KH is a rear bicycle hub. I didn’t take a picture that shows it but inboard of one flange the hub diameter is bigger … probably to accomodate a freewheel.


It absolutely makes sense to machine aluminum flanges that attach to a steel spindle. This is something I’ve been working on for ages, ever since around 1998, but couldn’t figure out how to do it in a cost-effective way for mass-production.

However, I now have an initial prototype made and you will hopefully see a production KH hub like this by Summer/Fall 2004.

Essentially the hub will consist of 3 pieces- two separate machined Alloy flanges that are internally splined, and a spindle with splines that extend all the way to where the inside of the flange would be.

The flanges press onto the axle just like the cranks do, stopping where the splines end on the inside of the flanges.

This means that the bearings will sit on splines, but the splined part fits 19mm I.D./40mm O.D. bearings perfectly so this doesn’t matter.

Overall it should save some weight and is a much cleaner design than anything currently out there.

Hopefully it works!

Kris Holm

Actually picture #4 shows the part of the aluminum hub thats larger in diameter.


Re: Dissected KH Hub

You know, a stainless steel KH hub would go great with a stainless steel KH frame. Now, if we could only find someone with one of those… :wink:

Seriously though, great pictures. I love reading your posts because it’s always interesting to see what you’ve been tinkering with. If you ever do decide to build a stainless steel KH hub and you want to let me test it for you, I wouldn’t object, but I already consider myself to be very lucky to have my SHaKH NaS setup.

Are the keys in the spindle inserted in the spindle or is the spindle and keys all one piece of metal? From the pictures it looks like the keys and spindle are all once piece of metal. That would be a bit inconvenient to machine.

what the hell happened to my Summit…? oh yeah.bought and paid for…:smiley:

i dropped on that hub many times,it doesnt look like i did a damn thing to it.with a sexier and wider hub body Profile may be superseded soon.all these advancements have happened as of late but Profile remains the same…


You told me you only rode the Summit to church on Sundays!


It depends on what the definition of “Church” is.

Besides… The Devil made him do it.

Any chance of a disk brake version? It would just take tapping disk mounting holes on one of the flanges, and it would make so many people so happy… :smiley:

The spindle is all one piece. Saying that the hub has six keyways really isn’t correct. I guess you would say that the spindle has six external splines and the hub has six internal mating splines.


It looks to me like the spindle has six internal splines and the hub has six external mating splines.