cylinders

hollow cylinder has to be machined first to make it hollow..

No it doesn't, tube can be made from sheet, which can then be machined if you need a particularly good finish or tight tolerance.

I depends on the design and application...the question is rather meaningless unless you specify a requirement.

Del

Also, those air conditioning ducts are made by spiral wrapping of sheet material to form a tube...

We do have some strange questions on here don't we?

"We do have some strange questions on here don't we?"

We do!

But, let's be a bit generous: My belief is that variance of sentence structure betw languages makes a simple query feel more odd than is the fact.

As Del said some materials can be formed. Also some like Aluminum can be extruded in to tube. It will depend what material you wish the tube to be made of and its usage as to what method will be used.

Steel tubing can also be extruded. If you need a seamless tube then DOM is the only choice. A piece of DOM tubing starts out as a welded seam tube or pipe. Then the tube is drawn through a die and also over a mandrel at the same time. After successive passes through progressively smaller dies the weld seam gets worked into the base metal.

Travis

I'm going to apologize ahead of time, but I just can't help myself . . .

If you need a hollow tube 2 feet in diameter with a 1 3/4 foot hole through it, I'd bet it would be a lot cheaper to buy it the way you want it rather than machine it from a solid bar.

Now, you can better explain what your requirements are, now that I've put forth a ludicrous example.

A solid rod is expensive if what you need is a cylinder. On the other hand a cylinder is expensive if a solid rod is required.

What was the question again?

Its also termed "Gunbarreling" not sure how its done, but to make drive shafts stronger, you convert the rod into a cylinder by Gunbarreling it.

you can also get CDW/ERW Cold Drawn Welded and Electrical Resistance Welded tube/pipe where the tube is created by rolling a flat material into a tube then welding the seam, then you have CDS or Cold Drawn Seamless where I think the tube is actually cold rolled, then honed and cleaned to remove the lip, this gives a consistant ID and OD to the tube.

A lot depends on the material and the requirements to form it to fit the requirements of the job.

Without the last requirement and at least a general idea of the material the first requirement is unanswerable.

Sorry we are not more help but more information is required

Brad

Comments about material are correct but also consider size & quantity. It may take more work to make a cylinder from solid but might still be cost effective if you have to buy a minimum quantity of extrusion or whatever to make a handful of parts.

This depends on Size, Qty req'd, & Mat'l.

Some sort of Forming is more economical in "use of material(volume)"; whether this is cost efficient for your application depends on: #pcs, cost of machining, &c.

Very large cyl.s might be best done by forming (roll & weld) even in single units; medium (say, 400mm) aluminum, by selelecting nearest stock extrusion.

Many variables here, specify more closely?

Hello

There is not enough information to provide an answer. I see others have used their gray matter to assume the sleeves usage.

Provide the correct information and we can provide an answer.

TeamSarge

If you have the rod but require a cylinder, coring the the rod you have may not be prohibitive in comparison to purchasing cylinder stock.

Is this the direction you are going?

i was thinking that , people use hollow cylinders to cut out cost, if stregth is not of that much concern,

then do they machine it, then how can it be cheaper,

suppose u need a rod of 30 mm diameter( stainless steel), but strenth is not important, and it could be worked with 5 to 7mm thick hollwow cylinder, then what is to be done

thanx for reply

if strength is not of that much concern,...

A cylinder will not be much weaker than the rod unless it has very thin walls.

Weight for weight it will be much stronger.

It all depends on what you want to do.

You're just asking if orange or apple is more expensive.

Weight for weight tube is stronger. Find a book on mechanics and do some reading. Most supporting structures use tubing instead of solid bar.

Tubes are not machined, they're extruded.

You asked, in effect: "Which costs more, a hollow cylinder or a solid rod? I'm thinking, that the hollow cylinder has to be [worked] machined first to make it hollow. Is my thinking in the right direction?"

Your thinking is correct...so far as it goes. Your question seems to be concerned, thinking-wise, with how you are evaluating the "trades" as to the cost, x, of provisioning a rod, as compared to the cost, y, of transforming and provisioning that that rod as a cylinder. (This would apply to a single rod or cylinder; if it were as respects a lot of the same, we would have to speak in terms of marginal costs; but let's not go there, just yet.)

As your question is predicated, the trade is between

• the labor, tooling, and waste (less immediate waste recovery value) costs of the cylinder

and

• the material cost of the rod.

Essentially (because other factors trade even), you would determine cylinder fabrication's waste recovery value (between more for thin wall cylinder and less for thick wall), and determine whether that recovery value is

• more than enough,
• less than enough, or
• just enough

to pay the additional tooling and labor needed to bore the rod to make the cylinder:

• if more than enough, then the rod is more expensive;
• if less, then the cylinder is more expensive;
• if just enough, then you break even (but only before marginal cost is taken into account).