how would you finish this bore?

[magu]

The rings will be o-rings, more than likely buna-n, because I can get them easily, it will be "pumping" ambient temperature air.

I hadn't considered galling, but it is a good point. The only reason I was going to use it is because I have a piece on hand. hmm.... I could bore it to 1.125", insert a press-fit bronze sleeve and open that up to 1"... It would leave a very thin wall, but should work.

 

[Robert LaLonde]

Buna works fine as a seal with stainless, steel, aluminum, etc. Buna is used as a seal at pressures upto 4500PSI in airguns. I tend towards Viton replacements, but viton doesn't perform as well at low temperatures. As a sliding element they may not last long without lubrication, but they will work. Fortunately since you are using an o-ring you can experiment with materials to see what works best, buna 75-90, viton, silicone, urethane... O-rings are readily available and relatively cheap in a number of materials. You can also consider double seals, x-rings, etc.

O-Rings are often uses in home made pneumatic cylinders. The best cylinders in my opinion are chrome lined, but often that puts a project outside the realm of the home experimenter unless they have a source for old hydraulic cylinders they can cut up for parts. To be fair their is many a small band saw with a home made air cylinder used as a feed regulator made out of aluminum with generic hardware store o-rings.

I have several low pressure plastic injectors with plain old Buna O-rings that are several years old. The cylinders and pistons are all aluminum and I haven't changed an o-ring in years. They get used with plastisol upto 350F, but pressures are admittedly relatively low. When I am leaning on one to fill a problem mold it might hit 50 PSI, but I doubt it.

 

[magu]

unless they have a source for old hydraulic cylinders they can cut up for parts.

That might be the golden ticket... I'll have to see if I can dig up a 1" cylinder to strip down. Even aside from the chrome bore, it would be less effort and waste to use that than to drill and bore out most of the material then fight to get a good finish...... Thank you for bequeathing you genius....

 

[Bob Korves]

Depending on the pressure expected in the cylinder, you might look into air cylinders, which are cheap and in the size range you are looking at. There are lots of choices of styles and end fittings. They will work as low pressure hydraulic cylinders (<200 psi) and are often used as hydraulic cylinders for adding a controlled down feed to a horizontal band saw.

 

[NortonDommi]

That damn cat! How many skins has it got left? What sort of pressure are you working with? HMWPE is cheap in cutting boards from your local $1,2&3 shop and makes great low friction bearings/packers for O-ring backup. Silicon greases are a big help where it is assemble and leave.
Aluminium Pnumatic tubing can be bought in Imperial and metrickery sizes with either a hard anodize or a hard chrome interior finish. A good place to enquire is at your local hydraulic service agent or Bearing Factor. Hydraulics, Pnumatics, Bearings, Seals & now electronic regulation & control are today so intertwined that any specialist shop or supplier wherever you live has access to information that as an individual you will never be able to access. Bonus is that it is a field that a lot of very smart people end up in and walking in with anything out of the ordinary or request for help usually results in a 'that made my day' moment for a very brainy person. Pays to do some basic research first ask a question or two and keep the taringa's,(ears), open.
I've often formed an idea of what I think will work and after a 5-10 minute talk with someone who knows their job have come away with something gaureenteed to work.
One thing I learnt very earley is that a good parts guy is worth whatever they ask for.
Sorry for the rant, little sleep

 

[Bmikkalson]

Hi, I totally know this is a old thread, but was wondering if you ever got the hammer done?