GXP Bottom Bracket Tool

One of my back-burner projects recently has been to replace the grease in my bike with something that will work better in the Cold. More on that grease later.

Getting at the bottom bracket bearings (the bearings that one’s feet spin around when riding a bike) involves a special tool, which I didn’t think to purchase on the way down here. So, I made one in our little machine shop.

First, some silly putty and a set of drill bits was used to figure out the size of the semicircular divets where the tool will push against the bearing carrier thingy. A similar technique was used to figure out how big of a circle the centres of the divets are located on:

bb tool 1

An astute reader might notice the snap ring; the bearings are pressed in, so the carrier needs to come out.


M, our machinist, found an appropriate bit of scrap steel to make the main part of the tool from and showed me around the lathe. Most of the machining work I’ve done in the past has involved high speed steel tooling, but M introduced me to the wonderful world of carbide insert tooling for this project. It’s pretty impressive stuff!

bb tool 2

Next was a bit of work on the mill to machine 1 inch hex flats on the back of the tool (to match with other Park bottom bracket tools) and to drill 16 countersunk holes to fit smallish screws; the screws would become pins to drive the carrier thingy. There was a fair bit of hand tapping involved, then another trip to the lathe to cut out a space for the carrier thingy to fit into. Finally, 16 beheaded screws were tightened in with a bit of epoxy on the threads so they wouldn’t go anywhere:bb tool 3

Learning from an earlier adventure that involved lathe-projected-shrapnel (read: beheading 16 screws in one go), I used a hacksaw to take most of the projecting parts of the screws off, then the lathe to finish the back of the tool:

bb tool 4

Probably the world’s most expensive GXP bottom bracket tool


About ianrrees

Nerdy guy.
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