Hi folks,
I'm just starting building my first frame, and tooling up for the job! What's the ups and downs between choosing a fixed 27.2 seattube reamer or an adjustable one? Which one would you recommend?
Thanks in advance..

Unless you are going to be building many frames a seattube reamer is an expensive tool to have. Better to just have a shop do it for you. It's also worth mentioning that some seat tubing actually already fits the appropriate sized seatpost without bothering to ream it to 27.2.
Easton Aluminum ultralight tubing fits 27.0 for example. The opposite end fits 29.8. Some of the other sizes of seatpost are a bit harder to find but that is a cheaper alternative.

IMHO adjustable reamers are an unacceptable compromise. I use a Cyclus 27.2mm seat tube reamer and it has held up well. At $129 ($82 for the handle and $47 for the reamer from Bike Tools Etc.) it is expensive, so as Canaboo says, you may want to just have a shop ream your frames for you unless you plan to build several frames or plan to build multiple frames using seat tubes that require several different seat post diameters.

There are a number of ways around this:

1) reamers are to restore a fitting dimension post heat, not to adapt ill fitting tubing. For one thing, you need to ream terribly deep if you want to conform a whole tube. While with the partial approach, you are only going to need to zap the area you heated.

2) If all you need to do is nudge a tight spot, that is something an adjustable reamer can do since, when it hits full wall size, you will note a different resistance, and can stop cutting, and test it. But using an adjustable to resize a tube is too imprecise.

3) Are you doing this for personal use, or for professional use. Certainly with the latter, as your eventual goal, you have all kinds of other aspects to financing your tools, and for the quality of work that will be expected.

4) I think it's 26.8 that fits standard 4130 tubing. With a lathe you can do some interesting things.

5) You can sleeve tubing and reduce the heat effects to the point where no reaming is required.

6) I use an adjustable reamer, but the reamer quality, sharpness in particular is not equivalent to good bike tools. It does work, I got the idea for it from a pro, but I will probably upgrade at some point.

7) In the amateur context, if you go the 10 dollar reamer approach, you need to plan your whole seat stay approach around it. To the extent you might want to design your stay attachment with no constraints, then you probably need the best tooling possible to restore the fit. That's probably another thread.

my experience is that adjustable reamers are ok. A lot of people hone after they ream to get rid of the cutting ridges.

Contrary to Scooper's HO, I've reamed hundreds and hundreds of frames with an adjustable reamer... no problems so far!

But Stan we can argue that one out when I see you at NAHBS.

I use a fixed 27.2 reamer. It's not that I really have anything against adjustable reamers, it's just that I'm extremely unlikely to ever have need for something other than 27.2.

And yes, I avoided buying a reamer for a long time, because it's something a bike shop does for cheap. But my results with bike shops doing frame prep has been mixed, to put it as politely as possible.

Tim, you're my guru, so no argument from me.

See you in Austin!

Thanks for all your extensive replies!

I'm inclined to buy a fixed 27.2 Cyclus reamer shortly.. It's not a big problem to spend some money where necessary, as long as it's wise; I've already bought a headtube reamer, so I've gone into the path already
Yes, maybe I can try to go with 27.0 for my first frame or so if the fit comes out acceptable.
Here is some further questions:

-I'm leaving the BB threader/facer to a later time, as they are more expensive and most of the BB shells threads/faces are ok to start with, and I'll try to preserve them that way (maybe I'm wrong for thinking that, don't know?)
-Will the finish of Cyclus reamer be sufficient for a good fit (without honing)?
-And is it correct to think that it won't be a problem to ream out the 27.0 inner diameter to 27.2? 0.1mm stock is such a small amount to cut, but a couple of above posts got me thinking..

For my future plans, I consider building frames for myself and friends. Maybe in the longer term (depending on my success ) I may consider building frames once in a while to sell. I'm using a wooden jig right now and thinking about gathering the basic dress-up tools very soon. As there's no shop here that's able to do these for me.

Thanks again for your help...

I own the head tube ones, and the BB ones, and use the cheapos for the seat tube. There are work arounds for the seat tube. I don't think you will find work arounds for the BB, with a few exceptions like using eccentric BBs with IGHs etc...

So if it were me, as it once was, I would put the money into something other than the seat tube.

As to can you ream out the seat tubes that much, I would guess you can, I ream out heavily when making internal sleeves. My only concern would be if it was tough to turn the reamer, and as previously mentioned, how far down you want to push the whole seat post and whether your reamer reaches. I'm sure it will be fine. Mainly, they sell seat posts in many sizes so I don't really know what you need to resize the tube for. The ones I get are either 27.2 or 26.8, for which seat postss are readily available

I also don't see a much way around a BB tap. You're gonna get a little bit of brass in those threads near the chainstay. Not to mention the distortion. Maybe if you are really really careful? Would be pretty tough.

Adjustable reamers are OK , particularly if you have the seat post in hand.

I have used them from time to time, last occasion 27.0>27.2, took it out just until the post fit, perfectly.

Best not to be in a hurry..

I agree, with the BB taps, in the Bike shops I worked in,
We built up a few prestige name Italian framesets.
the builders leave the chasing and facing the BB, reaming fork crown and head tube
to be done by the retailer..

I think part of the reason for that is to give the paint some time to cure in transit. If you do the facing before it's well hardened you can get some ugly results. Not such an issue these days with catalyst hardened paints and ovens, but older paints and small shops might not have had those luxuries.

I thought a thread clearer made out of a couple of "fluted out" BB cups might be sufficient to clear the brass (or silver in my case) I realize I still have to be really careful though. I just want to get through with my first frame with minimum investment. If I continue building frames (hopefully) there's no doubt that I'll soon need a BB threader.

BB facing is a must for alignment.

When you see the paint on the face of the BB, presumably (hopefully) it is after the bicyle has had its final alignment check, and is off to the paintshop. Pro builders would not let a bicycle leave the workshop and go out into the world without facing the BB after painting.

anyway try it, it is always something you can deal with if it doesn't work out. It's not like it will be built in and unchangeable.