Need for "oversized" 4130 tubing

We manufacture a part that is made from 1/2" 4130 tube with an .083" wall. I add several features, part to length and then send them out to be centerless ground to .4995". The problem is that we are having a hard time finding material that is large enough to grind to the final OD, since the entire OD must be ground. Ideally, we would like a .501" OD to start, but it seems like everything we order is on the low side of the tolerance (-.002" or more). For years (36 years and counting!) we have had contacts at suppliers that would measure a lot for us and we would buy the entire run when he found one over .500". We are nearing the end of our supply and need more soon.

Over the years these contacts have passed on and now it seems to be "you get what you get. +/- .005" and all of it seems to be on the small side. We use several hundred feet of this annually, and are not afraid to buy a large quantity when we find it. So does anyone have any contacts that they would care to share who might be willing to source this seemingly boutique material?

Regards, and thanks in advance!

Dependent on the total weight you may want to look into having a special mill run done. I find tubing always tends to run small so this would fall under the “special order” category.

Whysosharp said:

Dependent on the total weight you may want to look into having a special mill run done. I find tubing always tends to run small so this would fall under the “special order” category.

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Very "boutique" as steel tubing goes, though.

Call the "several hundred feet per year" an even one thousand feet @ sub .4 lb avoir per foot, and that's only 400 lbs of steel in a year.. or maybe two years? Or more years, yet?

No question it can be had, even if it were to be drilled and reamed from solid!

Fast, nor as cheaply as hand-picking from variation of a run?

Variation has become squeezed to the greedy side, already, industry-wide, of course, so most unlikely it will be coming back as an option - ever.

User has been lucky, so far. Now, not so much.

How long are the parts?

What happens yah run a right-sized mandrel or bearing-ball through the tube to make it a couple thou larger on the OD after spring-back? In-house op.

Not sure a finisher could be bothered with less than a thousand feet a year of a basic commodity steel.

Thanks for the replies so far. We use about 500 feet a year, and the smallest special mill run that we can find is 5,000'. Sadly, I can't convince the purchaser to just order us a 10 year supply.

The parts range in length from 4" to 20", and the majority of them run in the 4"-8" range. I have been pressing a slug through the shorter ones with undersized material, and this works fine to stretch the OD. The 8"-20" parts that are going to be a bear if we can't find a supplier.

You could look at a dedicated hydraulic station, either to expand set lengths into a bigger, robust limiting sleeve, or to press a ball through the tube. I would hope a 10K psi unit would be enough for ball driving without risking splitting an unsupported tube, but that's just a gut guess.

N54 said:

Thanks for the replies so far. We use about 500 feet a year, and the smallest special mill run that we can find is 5,000'. Sadly, I can't convince the purchaser to just order us a 10 year supply.

The parts range in length from 4" to 20", and the majority of them run in the 4"-8" range. I have been pressing a slug through the shorter ones with undersized material, and this works fine to stretch the OD. The 8"-20" parts that are going to be a bear if we can't find a supplier.

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You hadn't said the ID was crucial, so the expander is not a surprise.

On the long ones that won't stand that, scout about. A full-length drawing or expanding mandrel - "second op DOM" fashion - or something roller-ish with less infrastructure must exist. Once interviewed with a brand-new DOM plant, got the tour, but otherwise "not my rice-bowl".

No F(ine) Way you can be the first entity on-planet to ever have this sort of need though.

How critical is the ID? Could you start with .563" OD x .120" wall?

I used to draw tubing down a few thousandths with a round die and a rig I made for the hydraulic shaper to pull the tube. Never could get it to draw straight, the tube always ended up curved a little and then had to be straightened. Probably could rig up something to pull a ball through too. Just maybe get some assorted steel balls EDM'd with a through hole that you could pass a cable or pull rod through. They'll probably wear out quick. Probably have to pick and choose the ball size for a given batch of tubing, as well.
Baltec - Home

There are several good rifle barrel makers here in Wisconsin, talk to one of them about pulling a smooth "rifling" button though your material to size it up. Possibly make your own with a hydraulic cylinder and a piece of I beam. Rifling buttons are not that pricy.

Ed.

Thanks for all of the responses, folks. It pretty much confirms what I had suspected. We will either need to pony up the money for more processes (either expanding known tubing, machining out of a larger stock) or we will just need to have a mill run done in a "custom" size.

I'm not sure what the powers that be will decide, but I'm hoping for a mill run of larger material. As pointed out by several, the ID is not critical and pushing/pulling a slug through is an option. However in this situation, material delivered ready to use will be better for us in the long run.

Thanks again for the ideas and suggestions!

Do you know about Docol R8 tubing? It's touted to be a superior replacement for 4130N. I haven't used any yet, but it seems to be only made by SSAB and seems to be made by the same process, but perhaps something there will offer a source of slightly larger material -
Racing into the future with Docol Tubing - SSAB

They swage bike tubes into "double butted" and "Triple butted" form by pushing the tube onto a mandrel and necking it down with a mandrel, then rolling it to increase the diameter. See
Cycle Tubing & Tube Sets - Reynolds Technology

They do this with really, really nasty strong and hard steels (Chrome moly including 4130, Chrome manganese, Maraging stainless).

This might work, but it also might be more cost effective to buy a lot, use the oversize, and sell the undersize stuff.

bosleyjr said:

it also might be more cost effective to buy a lot, use the oversize, and sell the undersize stuff.

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I'm sure he (we) would go that route in a New York Minute, but..

The OTHER 102% of the market has been bitchin' for Donkey's Years about OVERSIZE stock messing up automated feed and collet systems more than undersize or "of course" - but perish the very thought you'd actually GET it - ON size.

And the bean counters have twigged to an RCH UNDERSIZE getting a few microns greater billable length each go and figured the extra buck-three-fifty a calendar quarter is a good move, too.

So "oversized" has gone serious scarce. Durex prolly has the same statistics, but their goods are "unit" priced anyway.

QED