Hi All,
I need to ream the seat tube on my first fillet brazed frame (27.2mm). I’m looking for budget tooling. Amazon has adjustable reamers for ~$30 like this one 26-29.5mm (Amazon.com: Rannb Adjustable Hand Reamer Square End Blade Reamer Adjustment Range 26-29.5mm/1-1/32" - 1-5/32" : Tools & Home Improvement). Is something like that good enough for an infrequent hobby builder?
Thanks!
-Jim G
I have this same type of reamer. I’ve never reamed a new frame with it, but I’ve reamed lots of vintage steel bikes out from 26.8 or 27.0 to 27.2 to have way more variety in seatpost options. So max I’ve done with it is reaming ~.016" diametrically in steel and it works good for that. It’s just hard to get it adjusted perfect.
I did it twice now with something similar. It worked. Takes some time because I’m constantly measuring as I creep up to the dimension.
Same as others. It works, I creep up on the diameter with seatpost in hand to test.
I do my seat tubes, head tubes, bearing seats, everything with adjustable reamers. Go slow, take your time, test fit a lot.
I have two adjustable reamers. They work well. If I could afford it I’d get a reverse spiral of the size I need. ie 27.2 If you can ream before you cut the slot for the seat tube. Makes it very diifcult to ream with the straight baldes. In my experience.
Also, if you accidentally slip a meaty part of a finger into that slot while reaming, it’s like removing a chunk of your finger with the worlds dullest scissors and it SUCKS.
argh crap dude! That would suck!
As @DEVLINCC said, ream before slitting, if your adjustable has straight blades (almost all do). A helical-blade adjustable is awesome, I have one in that size range, but I have heard they aren’t made anymore so finding a used one might be your only hope, and if it’s sharp, it won’t be cheap (and vice-versa).
If you have to ream with straight blades and the slit is there already, I bend the pinchbolt ears out ever so slightly so the blade isn’t cutting right there. The amount of bend or spreading you want is almost imperceptible.
It can also help to grind a small bevel on the inside of the slit. Like deburring only go further. Then when the blade hits, it’s hitting on a ramp instead of a wall at 90° to the direction of travel, which tends to stop the reamer dead in its tracks.
One more gotcha to avoid, if the frame has ever been sandblasted there’s probably sand in there, which kills cutters, so taking some time to push a rag down the tube first is worth it even if you don’t see sand. I push the rag all the way down, then extract it using a J-bend spoke — the spoke head hooks into the rag to let you pull it back out.
Luckily it was just my pinky. Hurt like hell, all full of metal bits and oil.
However, other than that, I’ve done my seatpost slit first every time and never had a problem reaming it.
I have a nice Cyclus reamer for 27.2, but a very cheap adjustable reamer just like that one for larger sizes (it’s actually made in India). It works absolutely fine. I had to make a sort of tap wrench type thing to go on the back of it (although you can also buy one I’m sure).
This procedure works for me:
Remember never to turn the reamer the wrong way. Always clockwise, whether it’s going in or out. This applies to all reamers.
If’n you’re slotting seat tubes yourself, leave a few mm un cut at the top. Pretty easy to cut and contour the last 3mm after while keeping the tool evenly engaged during the reaming. I seem to remember braze on seat collars that would leave a similar tab.
Pete
And use a heat sink at the tt/st/ss cluster if at all possible with tig
I fillet brazed my current frame, and I got a lot more distortion at the TT/ST/SS cluster than I expected. I might need to invest in a heatsink for this!
I noticed more distortion when I was a little careless about how “tight” my top tube was in my jig. The extra pressure due to the top tube being a mm or two too long I think contributed to the distortion I had on the seat tube. But I’m no expert either.
You don’t want a heat sink for fillet brazing. Heat control, technique and sequence is what you need. That’s not a ‘don’t rely on technology in place of skills’ statement (which I’d generally agree with if I wasn’t such a tool fetishist). The sink will suck the heat out of the joint and you won’t get the penetration you need of the filler.
Also, if you want, I have an adjustable reamer I’ll ship to you for $10 tomorrow. It was used once lightly. Send me DM if you want it.
@jimg did you sleeve the seat cluster? That’s what I’ve always done on my fillet brazed frames.
Hi Alex, No I didn’t sleeve the seat cluster – I used a seat tube with an external butt. (Nova CrMo Seat Tube 28.6mm - 9/6/1.2 - 580mm)
I wonder if those work better for TIG than fillet brazing? I’ve only used the sleeve on .9/.6 seat tubes. I hope it’s recoverable and still good to ride.
I sleeve the externally butted ones too. I do it as much for looks as strength.
