How to remove Internal weld bead from steel tube?

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Today I welded the headtube of the bike an disaster: I’ve now an Internal weld bead to remove from the headtube in order to accommodate the fork tube. I’ve tried to remove the bead by hand with: files for metals, wedge + hammer, metal saw but I didn’t succeed. Next option before cutting the tube and starting again is to buy hand drill flexible extension (to enter in the tube) and a 28mm flap wheel or metal hole saw for steel… but I’m not convinced. I’ve also thought to use Pillar Drill but I’ve not been able to image a way to block the bike frame on the table to let the bits enter the tube.

This are the dimensions: headtube inner diameter 28mm, the weld bead is approximately in the middle of 300mm headtube.

I’m posting here, maybe someone has solved this in the past or have any advice?

Thank you

A “standard” dremel flexible shaft is 26.x mm in diameter, so should fit into the tube.
What I can’t work out is how the spinning attachment could controllably make contact with the weld beads.
I have a Dremel, shaft and array of attachments that you could try (hopefully without destroying the flexible shaft).

I can leave them in the space tonight for you to try?

Alternatively, an abrasive rod longer than 300mm mounted on the lathe after passing through the bike frame. Spin the rod and gently wiggle the frame to make contact with the beads - terrifying!

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Whatever cutting bit you want to use, attach it to a long shaft and make some bushings to keep it centered in the pipe?


@Brendon_Hatcher thanks for the kind offer. Your dremel is way too precious to be used on the type of rough metal work I’m doing… I’ll try with a drill with a 300mm extension bit holder and keeping it in the center with the technique suggested by @tomnewsom. Thank you.

We have a flexishaft under the wooden bech next to the welding table. I’ll show you the trick how to use the drill as a motor. I suggest get a small white stone with an arbour.

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@Gergo_Dala you are a wise man, thank you! I’m need to buy the drill bit too, thinking this

thats an overkill, you cant really feed it in on the end of the flexshaft, and its shaft is too big too, it won’t fit
you need something like this, but have to check if it fits the shafts chuck , its abbrasive so will eat itself down without too much force.