Hydraulic cylinder shaft clearance to piston

L

Lanza

Aluminum

Joined

Jun 22, 2007

Location

Western Australia

• Sep 21, 2021

• #1

Is there any specifications chart on the shaft size to piston bore clearance. The piston bore has the triangular groove for an oring. I've been using h9 on the shafts. Reason I'm asking is because some of the shafts I get are more the h11 tolerance.
I have attached a rough sketch.


The parker handbook PG101 list the triangular chamfer, id say it would be the 3/32" CS oring size.
PG89 list the diametral clearance for the static seal glands.
https://www.parker.com/Literature/O-Ring Division Literature/ORD 5700.pdf

 

eKretz

Diamond; Mod Squad

Joined

Mar 27, 2005

Location

Northwest Indiana, USA

• Sep 21, 2021

• #2

Every one I've worked on has been a close slip fit. At that size I'd probably shoot for whichever tolerance level gets you to .0005"-.001" clearance.

 

B

BT Fabrication

Titanium

Joined

Nov 3, 2019

Location

Ontario Canada

• Sep 21, 2021

• #3

get as close as you can for a slip fit. most have an oring to seal it off anyways. id shoot for anything under 0.001"

 

R

R. Dan

Cast Iron

Joined

Sep 1, 2012

Location

NW Iowa

• Sep 21, 2021

• #4

.005 clearance nominal. Ø1.253±.001 on the piston i.d. and Ø1.248±.001 on the rod turndown. I would use a rectangular o-ring groove next to the piston rod shoulder. Easier to get the correct amount of squeeze on the o-ring. .06 radius where the rod turndown and shoulder meet. This is tried and true.

 

A

atex57

Stainless

Joined

Sep 6, 2006

Location

SW Wisconsin

• Sep 22, 2021

• #5

R. Dan said:

.005 clearance nominal. Ø1.253±.001 on the piston i.d. and Ø1.248±.001 on the rod turndown. I would use a rectangular o-ring groove next to the piston rod shoulder. Easier to get the correct amount of squeeze on the o-ring. .06 radius where the rod turndown and shoulder meet. This is tried and true.

Click to expand...

Plus one for that. ^^^^^

Making the rod to piston tight can make a problem when the nut is tightened and burrs the piston enough to lock it to the rod. I have worked on hundreds of cyls and have seen some pistons that needed a large hammer and punch to remove, some times you can use the head as a slide hammer.

Ed.

 

Phil in Montana

Stainless

Joined

Jul 31, 2007

Location

Missoula Mt

• Sep 22, 2021

• #6

size on size , heat to install...Phil

 

L

Lanza

Aluminum

Joined

Jun 22, 2007

Location

Western Australia

• Sep 26, 2021

• #7

R. Dan said:

.005 clearance nominal. Ø1.253±.001 on the piston i.d. and Ø1.248±.001 on the rod turndown. I would use a rectangular o-ring groove next to the piston rod shoulder. Easier to get the correct amount of squeeze on the o-ring. .06 radius where the rod turndown and shoulder meet. This is tried and true.

Click to expand...

I'd say your correct. The smaller pistons with a 1/2" shaft I'll make with less clearance.

 

B

Big Buck

Aluminum

Joined

Oct 27, 2005

Location

tc mi.

• Oct 26, 2021

• #8

I've built a lot of cylinders and , the m102 piston rods vary in size from 1.4985 to 1.5005 housing clearence should be .002 to.003 as the rods are usually out of round. Normally the 1.5 dia piston rod has a square cornor that sets on the face of the piston . I've seen oring grooves cut into the 1.125 dia or located at the end of the 1.125 dia & against the 1.500 shoulder and squeezed into the angle located on the piston , then use a unitork nut on the piston..

 

L

Lanza

Aluminum

Joined

Jun 22, 2007

Location

Western Australia

• Nov 20, 2021

• #9

I've been making hydraulics rods lately and have been following the parker ORD handbook, PG 89 on Industrial Static seal design
https://www.parker.com/Literature/O-Ring Division Literature/ORD 5700.pdf
For a piston and rod that uses a 1/8" CS o-ring groove in the shaft, it recommends 0.003-0.006" clearance (piston bore to shaft). I make rods from samples and a lot of them are about these clearance (1/8" CS o-ring). Most of the rods I manufactured are from 3/4"- 1 1/4" being K1045 material.