[How do I?] Enlarging the bore diameter of a 2-piece clamp?

[keeena]

I have a motorcycle bar riser clamp that I need to open up from 7/8" to 1-1/8". Each half of the clamp is a little less than half the circumference of the bar it clamps. i.e. the two clamp halves don't quite touch each other when bolting the assembly up on a 7/8" handlebar. A sample pic:



I'm thinking the proper setup would be to bolt the 2 halves together with shims between the clamps and then bore to exactly 1-1/8". Is this the right approach? And is the shim thickness important (I don't think it would be)? The shims would only be used for the machining setup, not in the final assembly.

 

[Weldingrod1]

Yep, shim it. Might also super glue the interface. Shim thickness needs to leave room to clamp.

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[MrWhoopee]

Your thinking is correct. Shim thickness should be the gap width when unclamped. Is there enough material to allow that much stock removal?

 

[keeena]

Thanks for the confirmation & help guys! Yes, on the part I have (its not the one in the picture above) there is enough meat to bore out to 1-1/8". My understanding is the OEM has a single mold/cast and they bore to 7/8" or 1-1/8" as needed depending on which bike the riser is going on.

I evenly clamped up a 7/8" bar to measure the gap and am making some shims for the setup. I'll post some pics when I start the work.

 

[rwm]

You could consider over-shimming it to preserve more metal if you think it might be too weak. i.e. shim it to fit a 1" bar?