Subject: nnnnnnnnnnRe: Polished steel shafts -How to?

From: Mike Pelelo <[email-masked]>
Date: Fri, 23 Dec 1994 11:11:05 -800 (PST)

Michael A. Pelelo
[email-masked]
4436 Van Buren, Sioux City, Ia. 51038
"There were a lot of things they didn't tell me 

when I signed on with this outfit."

On 22 Dec 1994, Flint Smith wrote:

> I'm working on a project that will have a pneumatically operated
> piston.  My concern is about wear on the sealing o-ring.
> 
> How is the high-polish on sealed shafts (automobile shock absorber
> shafts for example) achieved?  
> 
> 1) polishing  (mechanical removal of high spots)
> 2) plating    (deposition of a smooth layer)
> 3) de-plating (electrically removing high spots)
> 4) other?
> 
> Is chrome plating a good idea to reduce scratching from sand or dirt?
> 
> The project is still in the early conceptual stage, so any thoughts
> regarding sealing moving parts at high pressure (bbbbre (~300-500psi) would
> be appreciated.
> 
> Thanks, 

>      Flint    Smith               nm               bb         cc Smith
> 
Funny you should ask about this. I'm a design draftsman & I design 
hydraulic cylinders. Last night, I was quafing a few with some fellow 
eng. techs, and we were discussing rods and rod finishes. We chrome plate 
our rods, mostly in-house, although we do purchase some prechromed rod 
for use in our small bore facility. Our standard chrome is .0005/.0007 
thick. After we chrome, we grind and polish to 8/16 RMS. We use 
centerless grinders to do both our prechrome G&P and our finish G&P. We 
are currently fine-tuning a G&P machine made from a 1940's era lathe 
that is being used to create superfinishes (it can easily produce a 1 RMS 
& we are using it in production @ 2 RMS finishes.) The purpose of this 
glass-like finish is to produce an extremely dry rod, with virtually no 
stiction and no leakage past the gland U-cup and wiper seal. this is 
important in some environments, as oil obviously atrracts dirt. Hope 
this answers your finish question. As foraas sealing your piston at that 
high PSI, you might need more than a run of the mill O-ring ( usually 
a 70 durometer Buna-N material.) At the very le lleast you should use 
Hytrel back-up washers on either side of the o-ring to prevent extrusion 
of the o-ring in the clearance gap between piston & tube. However, this 
can create pressure trapping & you might blow the seal. You might want to 
try something like a capped t-seal or a teflon seal w/ a loader of 
some sort. Your best bet is probably to use a crown seal. Good sources 
for seals and info on seals are Parker-Hannifan, Macrotech, Shamban, etc. 
Let me know, and I will forward more info to you. Hope I helped.

---

From: [email-masked] (Steve Hampson)
Date: 23 Dec 1994 02:37:30 GMT

In article <[email-masked]>
Flint Smith <[email-masked]> writes:

> regarding sealing moving parts at high pressure (~300-500psi) would
> be appreciated.

Polished, chrome plated round stock is available by the foot from my
local steel supplier.  Look in the Yellow Pages for a dealer that
stocks tool and specialty steels.

--
Steve Hampson                           
Blue Sky Research
534 SW 3rd Ave
Portland, OR 97204
503-222-9571
503-222-1643 fax

---

From: Flint Smith <[email-masked]>
Date: 22 Dec 1994 02:08:51 GMT

Thanks, 
     Flint Smith

    mailto:[email-masked]

---

From: [email-masked] (Andy Dingley)
Date: Sat, 31 Dec 1994 20:22:57 +0000

> shafts for example) achieved?  

Grinding. One of the minor revolutions that made mass produced cars possible
was the Norton company's development of high speed grinding machines that
could simultaneously remove a sizable amount of stock from components like
engine valves, and simultaneously leave an accurate & fine finish. Read LTC
Rolt's "Tools For The Job" for the big story.

> Is chrome plating a good idea to reduce scratching from sand or dirt?

Hard chroming is there for two reasons; to stop rusting when the rod is
exposed for long periods (not needed if it's continually in use), and to
reduce scratching from odd grains of dirt etc.

Incidentally, hard chroming is a different finish from decorative chrome.
I don't know the details, but if you just ask a plater for "chrome plate" it
won't be wear resistant. You could try asking this over in rec.guns, where
they know about making chrome highly abrasion resistant.

> regarding sealing moving parts at high pressure (~300-500psi) would

Get a copy of a trade magazine like OEM Design (in the UK) and request all
the catalogues you can from seal makers. Most of these firms have tech
support staff who are *delighted* to receive unusual requests from
hobbyists or researchers.

Going to a big machine tools trade show like MetCut or Automan (Birmingham
NEC, UK) is also a fun day day out, and you'll learn a lot. A tiny amount of
social engineering will get you in the door, especially if you take a
few business cards along.

Now a question. I have a JCB backhoe digger (actually 3 of them) to restore,
and 2 of the 4 rams are knackered. It looks like grit particles have been
embedded in the seals and have scored through the chrome. After 5 years of
being parked in a hedge, the scratches have turned into rust pits. Any ideas
on restoration ? The budget won't cover new rams, and I'm unlikely to find
suitable spare rams. I can polish out the pitting easily enough to save the
seals from damage, but this leaves bare steel that will rust again in no
time. Any ideas for spot rechroming ?

--
Andy Dingley                             [email-masked]

Remember children:  'M' is for Monoculture and for Microsoft.