How to Ream a Bicycle Head Tube and Seat Tube

It's time to do some reaming, facing, and slotting on my mountain bike frame! First, you'll see me ream and face the head tube, then I ream the seat tube, and then I slot the seat tube.

So, for the head tube reaming and facing, I'm using a Park Tool head tube reamer/facer. In case you're not familiar with it, I give some background on the Park Tool reamer/facer, then I show the process for how to get a nice full clean up and make sure the headset will fit snug inside.

For the seat tube reaming, I used an adjustable reamer with straight blades that I'm actually not a huge fan of—but it was affordable. I also talk in the video about why helical reamers are better for seat tube reaming if you can afford one.

For the seat tube slotting operation, I use a homemade seat tube slotting tool that I made based on one I saw Drew Guldalian from Engin Cycles using.

[ambivalentnpc]

Hey, great vid!
Unless it has already come up, you could make the center hole in the aluminium puck of the head tube reaming setup somewhat bigger to fit the cone of the reaming too itself so that you would get the benefit of the spring action of the nut.
And another thing could be to make the height of the minor diameter of the shoulder longer so that the spacer registers in the headtube interior wall from longer distance. That would negate some of the possibility if the face of the tube is out of square to the length of the tubes centerline before the reaming is done.

[heyimamaker]

When I used to finesse the seat tube, we had a light abrasive brush that we put on a drill and gave it a few seconds. Worked like a charm.

[PithyBikes]

Great video Joe. I’m a huge fan of seeing for myself how bad (or good) a certain thing can be. No matter what I’m told, I just like to experience it for myself. And if shit hits the fan and it’s a disaster, I’ve always been able to take that real life experience and apply in other ways. Kudos for wanting to find out for yourself.

[besteriophonic]

how much I thought the cycle frame was easy in my mind . u changed everything about bike frame . but the mind, soul and heart u put I started liking you video . it usually very long .but I get ur deal now . best work .thanks

[milesfrank]

Love these vids... the quality of the information and the actual video quality is just bonkers

[doylerabjohn]

Very interesting....I have been concering having a custom frame built. Nice to see what go into building a frame. Thanks

[Sooperhans]

Love flex honing seat tubes on the lower end bikes at my shop. Makes me feel fancy lol.

[tobyvision]

I recommend tilting the seat tube so you are reaming "uphill" so that chips and extra oil tend to come down and out rather than into the frame. Not a big deal, but it helps a little bit when you are trying to clean out the seat tube.

[gpatrick]

I wanted to put a modern 30.9mm seat post in my old aluminum Specialized MTB which originally came with a 30.8mm seat post. I used the adjustable reamer and flex hone exactly as shown here, and got a perfect fit. Thanks a billion for the tutorial!

[tylersmalley]

I think I have binge-watched almost all your videos at this point. Keep up the great work! Just getting information at this point to build my first bike this winter.

[readrepairs]

So much useful and well thought through info. thank you for sharing

[beardoe]

A seat post really doesn't have a strength issue at the clamp, it has a stress concentration issue.

Rather than radius the bottom of a 1/8" slit, you should drill a 1/4" hole and slit in to that.

That will greatly reduced the chance of crack propogation from the end of the slit.

[modhappy]

Cobra Frame Building: Build first, Bike hard, No mercy.

[pack_yak]

great vid!
now that it's been a few years, have you come to a conclusion on your pressfit experiment? I know framework bikes is doing a pressfit on their machined alu BB lug but that's with very precise
machining as that's how most engineered parts work. Curious on what your experience was

[essendossev]

Can you do something like this for removing an old seat post that has seized up in the seat tube?

[AndrewBlucher]

Glad I found your vid Joe, good work. It's six months later; how did the press fit pan out?

[macendy]

Hi Cobra! I am in the process of building a frame and relied on LBS for reaming and facing. Now I figured out they misuderstood what I was asking about and they could probably face my head tube and BB, but not ream it. I really do not feel like spending few hundred bucks on reamers for frame nr. 1. Maybe later. I need to ream standard 44 mm head tube and press fit BB92. Is it worth trying with adjustable reamer as you did with the seatpost? Thanks!

[blechnik]

thank you for the great explanation! Do you do anything to the seat tube before reaming to remove any small bumps that might be there from welding?

[BruceChastain]

for the seat tube, would a "Flex-Hone Tool" on a cordless drill work?

[SandyfordService]

hi, i've recently got a scott team racing alloy frame that fits a 26.8 and 31.8 collar obviously thinking of reaming it to fit a 27.2 dropper i've calculated the inside to be roughly 2.6mm thick. is it okay to ream it?