What is the correct grit hone for an air cylinder.

[craigfperry]

that uses a parachute type seal.

 

[FredGarvin]

Hi Craig,
I must admit, I can not say I am familiar with the term "parachute seal." Perhaps I know it by a different term? Once I know that I'm sure we can track down the right info.

 

[craigfperry]

i'm sorry i don't know the correct name.
here is a pic of the seal.
it goes on a dovetail at the front of the piston.
i'm not sure but i would guess the durometer to be about 70.
and the cylinder is regular steel.
thanks.

 

[Ranger Mike]

1200 grit
see www.batestech.com
experts at honing..sunnen hone is the bible in racing..

 

[FredGarvin]

I would double check that number. It sounds awfully high. I haven't been able to find anything as of yet other than this reference from flex hone.

http://www.flexhone.com/flexhone%20for%20cylinders.htm

They don't even go up to a 1200 grit hone and they're talking about an 800 grit being an Ra = 3-10. Many elastomeric seals require some surface roughness to operate correctly, especially with liquids. Since this is an air application the question arises do these seals need oil entrained in the air for seal lubrication (they are dynamic seals).

Do you know the manufacturer of the seals or the actuators?

 

[Ranger Mike]

correct
thats why i recommend he contact theweb site and talk to appliactins engineers who deal with this..i can spend a lot of time discussing surface texture and various parameters Ra, RMS, Rt RV Peak Count etc..but he needs to tel the A.E. the type steel and coating if any and fluid for more help

they do make 1200 grit..
might fine

 

[craigfperry]

thanks for the links this gives me a place to start.
i do know that i do need some lube to remain in the crosshatch to lube the seal.

these seals are for a pellet gun, the maker is Jim Maccari.

 

[turbo]

thanks for the links this gives me a place to start.
i do know that i do need some lube to remain in the crosshatch to lube the seal.

these seals are for a pellet gun, the maker is Jim Maccari.

He is out of commission with a severe back injury. Are you going to do the repairs yourself?

 

[craigfperry]

yes i have rebuilt a few of the airguns i have.
but the best info i can get is a crosshatch of 400 grit which i am not happy with those results as far as seal wear and overall preformance.
it seems to me an 800 grit may be better.

the other thing that puzzles me is with the 400 grit crosshatch after a few hundred rounds thru the gun the crosshatch is gone and the cylinder walls are polished to a mirror finish.

 

[FredGarvin]

the other thing that puzzles me is with the 400 grit crosshatch after a few hundred rounds thru the gun the crosshatch is gone and the cylinder walls are polished to a mirror finish.

What is the barrel made out of? It seems like the surface hardness of the bore is too low.

 

[craigfperry]

i would say not high quality, i don't know enough to guess.
the guns this happened to were made by Crosman with parts made in china.
i am about to try a reseal on a spanish made gun and from what i have seen they seem to be made better.