brake caliper pistons :stainless grade

[Shox Dr]

Looks like most aftermarket pistons are machined out of 303, but 316 is the better choice for corrosion resistance.

So 303 for better machining with a slight loss in salt resistance, or 316 with its trade offs.

I'll be machining them no access to grinding, and while I'd like a grinder setup for the lathe. It's not happening on mine after I've just rebuilt it

 

[mike 109444]

Are you going to be able to get the "ground" finish? Or are you goung to end up with what feel like a fine finish but under magnification will look like the surface of a file! This will be rubbing against the seals...... Do you have one of the surface scratch comparison checker things (cant recall name it's beeen a longggg time since my apprenticeship. Wet and dry will only take the tops off the ridges. Maybe rough out (+ 010") then send for grinding?

 

[brightspark]

after turning make some cast iron adjustable sleeves and lap them with grinding paste http://modelenginenews.org/duplex/duplex_laps.html

 

[Lawnmowerboy]

If you can get it pretty much on size polish them up with some 800 grit emery.

 

[hotrodder]

I'll be machining them no access to grinding, and while I'd like a grinder setup for the lathe. It's not happening on mine after I've just rebuilt it

1 You clearly need to own more lathes
1.5 or a centreless grinding set up
2 Titanium would fix the corrosion resistance dilema and has the added bonus of lower thermal conductivity

Sorry, nothing useful to add that's based in the practicalities of the real world

 

[armalites]

I've have machined caliper pistons from 304 stainless on my Myford 7

With the right speed I am able to get a nice finish on the finished item.

Back gear was needed on the larger ones.

It's hard work on the Myford as I needed to make very light cuts and loads of passes. I was using TCT tooling and I got through quite a few tips.

I wouldn't call myself an experienced machinist.

One thing to remember is 303 is still going to be better than steel for corrosion resistance.

 

[Big Pete]

I've machined them from 304 on a colchester student, finished them with emery tape. Didn't have any seal issues.

 

[langy]

I've made them in 316 only, never found any problems once polished.

 

[dan.taylor.1]

If you think about it the tiny ridges will be inline with the seals not in and out if you get me so sealing shouldnt be an issue. In reality ive seen some hellishly pitted examples not leak before now, quad bike calipers on salt marshes..!

Dan

 

[armalites]

If you think about it the tiny ridges will be inline with the seals not in and out if you get me so sealing shouldnt be an issue. In reality ive seen some hellishly pitted examples not leak before now, quad bike calipers on salt marshes..!

Dan

I have to agree with Dan, I've taken sticking rusty pistons out and cleaned them with wet and dry, cleaned the seals and put them back and they worked 100%.

Caliper pistons only move a very small amount as the pads wear and probably the reason they go rusty and stick.

 

[mike 109444]

Think you will find the piston goes in and out and rubbes against the seal and the machining will leave lines (albeit fine) like a thread. Yes you may get a good finish by polishing and yes I have seen some rough pistons (corroded) that were still working but when you stab your foot on the break do you want to ask yourself "do you feel luck pun.... well you know the rest of the quote : )
First section I got put on when I was an apprentice (and not at collage) was the cylindrical grinding. Scared the sh*t out of me. Still you did get a bottle of milk each day : )