Steel tubing manufacture

Stephen Kuzara

Registered
Registered
Joined
Apr 22, 2021
Messages
6
I am wondering/trying to find info on how precision tubing is made. By precision I mean plus or minus .0005 of the desired size with similar concentricity. Size 3/8 to 1/2 inch OD with ID at 1/4 and 2 inches in length. I can't seem to find a manufacture for such. Stephen
 
that is quite a tight tolerance, you might need to have stock tube worked on in some way.

Stu
 
We made some lengths of tube with tolerances like that....
I started by gun drilling a hole through the over size round stock approx 32 inches long then passed them to the tool room supervisor who put them on a custom made mandrel to turn the O.D. concentric with the I.D..........
They were expensive, a Beryllium project that the companies three shop supervisors did all the work on.
Don and Gary both passed, leaves me.
 
There are several methods, most involving a mandrel of appropriate size. The first point is whether it is seamless or seamed. Seamed being the easiest/simplist. Back in the dark ages BC (before computers), even before electricity, gun barrels were wrapped in a spiral around a mandrel and beat by the smith to 'weld' the seam. The mandrel forming the bore. . .

At work (before retirement), we used a seamless stainless tubing for instrument work. Nominally for treated water or for dried air. Occasionally for other 'fluids'. The OD was within a thou tolerance, the ID was not that important, it might vary a couple of thou here or there. The OD of 1/4 inch, .250 with an ID of 3/16, .1875 would pass a BB shot of .177 with consistancy. It was produced from semi-molten (called plastic) metal being forced out of a 'collet' with a hardened mandrel inside to adjust ID. The metal was quick chilled (solidified) shortly after exit. Soft copper tubing is made by a similar process. Hard copper (pipe) is seamed. It is smooth but under stress the seam will reveal itself. Iron/steel pipe is the same. They are both rolled from flat stock until rounded. Then welded, either electrically or with pressure.

At the "Pipe Shop" (foundry), ductile iron pipe was cast. Early on with pouring vertically, later by the DeLaVaud 'spin casting" process. At USSteel's pipe mill, drill casing is made by piercing a solid billet with the 'piercing mandrel' then spun up in a semisolid state. In both cases, the result was six or eight inches diameter and larger, and certainly not to your specifications.

Modern day gun barrels (small bore) are drill lengthwise, then reamed and rifled. Larger guns like coastal guns and ship guns are cast and then milled to exact size. Of the many processes, part will be "proprietary". Either in the process or the metalurgical makeup of the tooling.

You could start by looking for "instrument" tubing. For the short lengths desired, it might be better to do the 'finish' work yourself. Turn a piece of tubing to the appropriate OD, chuck in a collet, and ream to the desired ID. For the small diameters you mentioned, the cost of "DIY" would be a small fraction of the cost of instrument tubing. Years back, I had need of the 1/4 inch tubing. The supply house quoted for (minimum) 20 foot lengths in 100 ft bundles. I ended up "misallocating" what I needed, far less than ten feet. The price from 25 years back would be irrelevant today, but was atrocious.

Depending on the application, there is also glass and plastic tubing, such as found at chemistry supply houses. They could neet your tolerences but would not do good for mechanival motion.

.
 
that is quite a tight tolerance, you might need to have stock tube worked on in some way.

Stu
I actually intended to ream to .254 or so and hone to 6.5mm with a Sunnen guide hone. I need to produce a very tight tolerance on the inside. The OD is not so size critical ( plus or minus a couple thou) just needs to be concentric. I was hoping to find reasonably good stock to start with and I would do the rest.
 
We made some lengths of tube with tolerances like that....
I started by gun drilling a hole through the over size round stock approx 32 inches long then passed them to the tool room supervisor who put them on a custom made mandrel to turn the O.D. concentric with the I.D..........
They were expensive, a Beryllium project that the companies three shop supervisors did all the work on.
Don and Gary both passed, leaves me.
I like the idea of finishing the inside to desired specs and then grinding the OD, probably the easiest way to insure concentricity.
 
There are several methods, most involving a mandrel of appropriate size. The first point is whether it is seamless or seamed. Seamed being the easiest/simplist. Back in the dark ages BC (before computers), even before electricity, gun barrels were wrapped in a spiral around a mandrel and beat by the smith to 'weld' the seam. The mandrel forming the bore. . .

At work (before retirement), we used a seamless stainless tubing for instrument work. Nominally for treated water or for dried air. Occasionally for other 'fluids'. The OD was within a thou tolerance, the ID was not that important, it might vary a couple of thou here or there. The OD of 1/4 inch, .250 with an ID of 3/16, .1875 would pass a BB shot of .177 with consistancy. It was produced from semi-molten (called plastic) metal being forced out of a 'collet' with a hardened mandrel inside to adjust ID. The metal was quick chilled (solidified) shortly after exit. Soft copper tubing is made by a similar process. Hard copper (pipe) is seamed. It is smooth but under stress the seam will reveal itself. Iron/steel pipe is the same. They are both rolled from flat stock until rounded. Then welded, either electrically or with pressure.

At the "Pipe Shop" (foundry), ductile iron pipe was cast. Early on with pouring vertically, later by the DeLaVaud 'spin casting" process. At USSteel's pipe mill, drill casing is made by piercing a solid billet with the 'piercing mandrel' then spun up in a semisolid state. In both cases, the result was six or eight inches diameter and larger, and certainly not to your specifications.

Modern day gun barrels (small bore) are drill lengthwise, then reamed and rifled. Larger guns like coastal guns and ship guns are cast and then milled to exact size. Of the many processes, part will be "proprietary". Either in the process or the metalurgical makeup of the tooling.

You could start by looking for "instrument" tubing. For the short lengths desired, it might be better to do the 'finish' work yourself. Turn a piece of tubing to the appropriate OD, chuck in a collet, and ream to the desired ID. For the small diameters you mentioned, the cost of "DIY" would be a small fraction of the cost of instrument tubing. Years back, I had need of the 1/4 inch tubing. The supply house quoted for (minimum) 20 foot lengths in 100 ft bundles. I ended up "misallocating" what I needed, far less than ten feet. The price from 25 years back would be irrelevant today, but was atrocious.

Depending on the application, there is also glass and plastic tubing, such as found at chemistry supply houses. They could neet your tolerences but would not do good for mechanival motion.

.
There are several methods, most involving a mandrel of appropriate size. The first point is whether it is seamless or seamed. Seamed being the easiest/simplist. Back in the dark ages BC (before computers), even before electricity, gun barrels were wrapped in a spiral around a mandrel and beat by the smith to 'weld' the seam. The mandrel forming the bore. . .

At work (before retirement), we used a seamless stainless tubing for instrument work. Nominally for treated water or for dried air. Occasionally for other 'fluids'. The OD was within a thou tolerance, the ID was not that important, it might vary a couple of thou here or there. The OD of 1/4 inch, .250 with an ID of 3/16, .1875 would pass a BB shot of .177 with consistancy. It was produced from semi-molten (called plastic) metal being forced out of a 'collet' with a hardened mandrel inside to adjust ID. The metal was quick chilled (solidified) shortly after exit. Soft copper tubing is made by a similar process. Hard copper (pipe) is seamed. It is smooth but under stress the seam will reveal itself. Iron/steel pipe is the same. They are both rolled from flat stock until rounded. Then welded, either electrically or with pressure.

At the "Pipe Shop" (foundry), ductile iron pipe was cast. Early on with pouring vertically, later by the DeLaVaud 'spin casting" process. At USSteel's pipe mill, drill casing is made by piercing a solid billet with the 'piercing mandrel' then spun up in a semisolid state. In both cases, the result was six or eight inches diameter and larger, and certainly not to your specifications.

Modern day gun barrels (small bore) are drill lengthwise, then reamed and rifled. Larger guns like coastal guns and ship guns are cast and then milled to exact size. Of the many processes, part will be "proprietary". Either in the process or the metalurgical makeup of the tooling.

You could start by looking for "instrument" tubing. For the short lengths desired, it might be better to do the 'finish' work yourself. Turn a piece of tubing to the appropriate OD, chuck in a collet, and ream to the desired ID. For the small diameters you mentioned, the cost of "DIY" would be a small fraction of the cost of instrument tubing. Years back, I had need of the 1/4 inch tubing. The supply house quoted for (minimum) 20 foot lengths in 100 ft bundles. I ended up "misallocating" what I needed, far less than ten feet. The price from 25 years back would be irrelevant today, but was atrocious.

Depending on the application, there is also glass and plastic tubing, such as found at chemistry supply houses. They could neet your tolerences but would not do good for mechanival motion.

.
I thought about using ss, I wouldn't mind the extra cost either. There are a number of parts to this device and this is the one part that most people who make this have not been able to make good consistently. I don't want to say what it is just yet but it spins at a fairly high RPM.
 
I actually intended to ream to .254 or so and hone to 6.5mm with a Sunnen guide hone. I need to produce a very tight tolerance on the inside. The OD is not so size critical ( plus or minus a couple thou) just needs to be concentric. I was hoping to find reasonably good stock to start with and I would do the rest.

I did not know they did that type of hone that small :)

Always the option to make a lap from aluminum bar for the id also.

Stu
 
Back
Top