I picked up a Cyclus headset press from bike-components.de and it was delivered today. I am installing a Cane Creek 40 1" threadless headset on my Fondriest frame and I've not used a press before. This one has the stepped guides top and bottom. The cartridge bearings come out fairly easily.

It makes sense to press one cup at a time, just to avoid having to line up both cups precisely at the same time. Grease on the outside of the cup where it enters the headset, and grease on the threads of the press too. The stepped guides should keep everything in alignment. Maybe after a few headsets' worth of experience, doing both at the same time would be OK - but I'm thinking not the first time.

Any gotchas I should know about before it do this?

I've done it both ways but now almost always do one at a time.

I find it weird that it's pretty well understood you should do one cup at a time, but nobody sells a press that's setup to do that. Shouldn't the press come with one stepped press adapter that is for the cups, and a second one that's a pilot for various head tubes?

I don't know about the Cyclus headset press, but doing the big bolt with fender washers press the big gotcha tip is going very carefully and stopping if it looks like the cup isn't perfectly aligned.

I have installed nearly every one of the dozens I've done with both cups in place. Using Park, Campy, Bicycle Research, Var, various OS adaptors on old 1" presses, bench vices and likely other tools I've forgotten about. I will say that aligning the cups coaxially is the key and those "presses" that lack a piloted cup block need slight cup engagement then tool backing off and repositioning to correct any cup angularity. The usual time I've done one cup at a time is when I've used a hammer and 2x4 block of wood.

But the war goes to those who do the install straight the first time, no matter how one gets there. Andy

The Campagnolo #733 headset press uses a conical piece (#733 /14) to center the non-cup end of the tool in the head tube when pressing in one cup at a time.

Interesting, that's one of the few headset press tools I've never handled.

One of those ebay bike tool guys does sell head tube pilots, for the Park set I think.

This Park Tool video shows doing it both one at a time and both:

I pressed the bottom and top cup separately, in that order. It didn't take long and the press worked perfectly. Now I'm off to the hardware store to get a small length of pvc to seat the crown race. Not knowing how well the pvc will take the pounding, it may be a one-use tool, but that's OK. It's a 1" steerer, and this is my only frame that uses that size. It will probably be a one-use tool anyway, for that reason. But you don't know what frame/fork might be joining the herd down the road, so maybe not.

Thanks for the replies, that's one task finished up.