Cylinder question

Guys my brother is rebuilding the hydraulics on our 9N and the ID of the lift cylinder looks like this. He has already hit it with a hone but it has some deep scratches. Is there a max ID bore before it needs to be thrown away. He is changing it out with a new piston and O ring instead of the metal rings. What do yall think

I asked the same question a while back; this is what The Old Hokie said:

" I can give you some general inspection guidelines - assumes a dynamic seal using a small (<.250) cross section o-ring. Mic the piston and add .008 (.004 sidewall clearance) to that measurement and you won't be far off. Plus a max of .002 out of round or taper. Cylinder ID should be scratch free with a 16u RA or better finish. That's actually pretty generous - a modern hydraulic cylinder finish is on the order of 4u RA.

Those clearances are crude approximations based on standard gland design practices. For a more reliable number you really need to measure the o-ring and the dimensions of the gland on the piston then compute the bore needed to get 40%-75% gland fill.

Or just use a new cylinder and trust they got it right.... "

Personally.......I'd just buy a new cylinder!
75 Tips

Yes it is time for a new one...

Get a new cylinder. The scars are what happens when the hold 3-ring piston runs with no or low oil in the system. Honing won't help much if at all, and since the grunt work is already done i.e. top cover off, cylinder off, et al, then do it right the first time and save the headaches of having to pull it all apart in a month, two months, a year, whatever. I once took my old 8N scarred cylinder and rebored it on a Bridgeport, made my own custom cylinder to fit the new bore, and installed my own new O'Ring and wiper. Nowadays, I don't have the patience to do that -tramming in the cylinder square and perpendicular in a special jig which I also had to make. You need to get a new cylinder; the NAA-530-D piston; the NAA-533-A O'Ring; and the NAA-437-A wiper -SEE LINK. Be aware the 9N and 2Nhydraulic top cover and linkage are different than the 8N system. There is a special "wishbone" link that if not removed and installed correctly will break and cause unnecessary additional work, time, and money. Got an I & T F-04 Manual?


[i:654c4848f0][b:654c4848f0]<font size="4">Tim *PloughNman* Daley(MI)</font>[/b:654c4848f0][/i:654c4848f0]<table width="100" border="1" cellpadding="0" cellspacing="0" bordercolor="#000000"><tr><td height="25" colspan="2" bgcolor="#CC0000"></td></tr><tr><td></td><td></td></tr></table>
Hydraulic Cylinder

This one might work with the steel rings but it will destroy the new O ring in a hurry.
Replace the cylinder.

Dirt is what gets it and will be what gets it again.