Originally Posted by DocRay
whoa. really dumb idea. Danno, I wish you would stop making thes types of suggestions without knowing what you are talking about.
You want to remove only the corrosion, not ream out the tube, that will weaken the tube and make proper seatpost fit impossible, ruining the frame.
LIGHT abrasive to remove any rust, then you can try a light coat of clear laquer to seal, make sure it dries for days, then a new seatpost with lots of grease.
So I take it you've never ever used the hone before and yet you pass judgement on my 10-years of using it a shop, eh? Blanket, all-or-nothing, black & white statements can't really compare to actual numbers. Here's what a brake-cylinder hone is used for:
- master-cylinders in cars have piston pushing inside a bore with 0.0010-0.0015" clearance.
- this gap is sealed with a rubber O-ring that's riding in a groove at the end of the piston
- brake-fluid is anhydrous and absorbs moisture from the air.
- over time, a year or two, the brake-fluid absorbs enough moisture that it actually starts to percipitate out of the fluid under cold-temperatures
- these droplets of water eventually corrodes and rusts the walls of the master-cylinder
- the corrosion and rust chews up the rubber O-ring and you end up with soft brakes, the pedal may even go all the way to the floor in extreme cases
- So... you repair the master-cylinder by disassembling and using the brake-cylinder hone on the corrosion and rust present in the cylinder.
- with WD40 or cutting-oil, 30-seconds with the hone typically removes 0.0002" of material (at minimal spring-tension setting). Usually a good idea to measure the cylinder and piston beforehand to ensure maximum-clearance of 0.0030" is not exceeded in the process of honing (reduce honing time if clearances are close to the limit already).
- replace O-ring on end of piston with new one,
- reassemble brake master-cylinder, pour in new fluid and you've got new brakes!
Note that the surface created by the hone is smooth enough to seal against 1300psi of hydraulic fluid with just a rubber O-ring!
With a seattube and cutting-oil, 10-20 seconds of the hone typically won't even remove the primer-paint that's sprayed down there! But it really does a nice job on the soft porous rust and other corrosion. It's much safer than reamers. You have to be careful with those and adjust them to the minimum since just 1/4-1/2 of a turn can take off 0.0020" of material instantly.
Next you're gonna tell me that programming the mill to take off 0.0005" from the surface of a corroded seat-post in my lathe is a dumb idea too right? After all you've probably done it a thousand times...
