How Would You Make These ?

I've been asked by a mate if I could make a few pairs of these items for him as they are horrendously expensive to buy. They're handlebar risers for a BMW motorbike & he reckons they're practically essential fitment on his particular model.

I've got my own CNC mill & could tackle the clamp quite easily if it weren't for the upright stem.

I'm not an engineer, I'm very much at the bottom of the learning curve & the more I try to think about how to machine them the harder it becomes.

Perhaps that's why they're horrendously expensive???

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I'm not after a comprehensive step by step, just a few pointers before my head explodes.

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before my

I'd assume it was milled from either a solid billet or possibly a forging - the upright stem can be milled like the rest of it. It may be a two part process. a/ Mill the stem from the billet b/ invert the result in a fixture using the stem to hold it and mill the clamp.


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Andrew Mawson

I reckon it was most definately milled from solid billet, but what length tool would you need at some point of the operation??

I think that upright stem has been lathed & that's the bit where it gets komplikated for a simple bloke like me.

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I assume the riser is for both extra height, and different reach? If not then a rise only is (relatively) simple, get oversized bar, large enough to contain the split clamp and turn the rise to a bit oversized (allows for cleanup later). then reverse and bore the pocket. create the split clamp. then fit sacrifical bar in chuck, turn to size, clamp riser over and finish spigot to size.

now if its for reach as well then bore pocket in a large lump of metal, split and form clamp. turn fixture spigot to size, drill and tap, then bolt to a faceplate at the appropriate offset, clamp on metal and turn the new spigot

lots of detal steps skipped, but basic workflow that should give required result

Disclaimer: This advice is worth what you paid for it, If you break anything you get to keep both halves.


Reply to
Dave S

Looks like it's machined from a solid billet. Can't see any problem with machining it all from one side (if you have the right tools and big enough machine). Then slotted and drilled as a second op. I'd be more concerned about exactly what it's made from, as this is a safety critical component -failure of which could easliy result in death or serious injury. Poor machining (leaving small notches or marks on the surface) could result in cracks developing as well. I'd say this is a case of if your not sure of everything leave well alone.

Regards Kevin

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Make 'em in two parts - put a hole in the outside bump of the clamp, make a second cylindrical bit with a stepped diameter, the smaller one to fit the hole in the bump. Make that portion a little shorter, weld it in.

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That is quite possibly the most sensible thing I've ever seen written on the Interweb :-)


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