How are suspension tubes made?

[5ivemachine]

Hey everyone I've tried to research this topic and haven't gotten anywhere really. I come from the mountain bike world and have always wondered how the Stantion tubes in suspension are manufactured to such a tight tolerance in such high quantities. Basically think of an aluminum tube 38mm in diameter, 12 inches long with a tapered or butted end with a perfect ID. The ID needs to be perfect as an air spring travels along it so it needs to be smooth and accurate, same for the outside. Honed? Reamed?

 

[Orange Vise]

The ID just needs a fine enough surface roughness to hold air with rubber shaft seals.

Honing would be my best guess. OD is likely centerless ground. Both processes are highly repeatable and low cost in high quantities.

 

[5ivemachine]

Yeah honing was my guess too.

 

[Vancbiker]

I believe the ID is roller burnished. When I have had my Fox Float apart, no honing marks were visible.

 

[Cole2534]

The shock bodies I've been in, though not MTB forks, have all been honed and very smooth with no visible hatch marks.

 

[BT Fabrication]

same as hydraulic tubing. just a honed interior and or centerless ground exterior.