STandard Allowances on Bar Stock O.D. & Length 4

[Quazif]

I am looking for a standard for selection of raw material(Bar Stock), based on the material condition (Hot Rolled, COld Drawn, Turned & Polished e.t.c.) and the O.D.

In our work place it is just done by the word of mouth (senior most guy tells you what RM size to use).
I would like to find a specific reference to use on long running & high volume jobs.

Thanks

 

[MadMango]

Allowances are dependant on the mill, unless you specify ASTM standards they have to meet.

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[metrat]

There are a wide variety of industry standards that address tolerances for bar product, based on finish conditions (hot rolled, cold finished, ground, etc.)

You may want to look at some of the ASTM specifications, these are generally separated by product type, and the tolerances will be within those particular product specs.

There are also AMS specifications that are a bit more general, not specifically tied to a particulat product, such as AMS-2251 or AMS-2253. Thes might provide a reasonable starting point.

 

[TVP]

Quazif,

ASTM A 29/A 29M is the North American standard for hot-rolled steel bars, and it has information regarding alloys, sizes, tolerances, etc. ASTM A 108 covers cold-finished bars. You can obtain them directly from ASTM.

 

[Quazif]

Thanks for all your inputs, but I believe that I did not state my question correctly.
Say I have to finish turn a 2.5" OD 4140 Steel (or any steel Hot Rolled or Cold Finished).
What size Bar stock do I buy. Usually people just go to the next bigger standard size.
But is there a scientific way or a Table or Standardto calculate Raw Material Size based on your finished size and type of material..

 

[metrat]

There are also specs that control the depth of surface defects, such as laps, decarb and other items. Often people will evaluate the size part the want to mfg. then see the defect depths that are permissible and add that to the stock sizr, plus a bit of a safety factor. One spec that deals with this is AMS AS-1182.

 

[lewtam]

MadMango is right - it's very dependant on the manufacturing route taken before the bar stock gets to you.

The above mentioned standards will give you tables of machining allowances and dimensional tolerance on the diameter of bar stock, but these are very generous and in a commercial manufacturing environment are sometimes considered uneconomic.

You need to consider other variables - what size is the production run? How critical is the 2.5" OD and over what length? It might be more economical to purchase preturned or preground barstock and let your vendor make the decision on what original hot rolled size they use.

One component a previous employer manufactured was induction hardened pins for mining applications. When I got quotes for material from vendors I would stipulate something like 'material to finish dia 2.5" h9 X 400mm length. QTY 500'. With eddy current crack detection as our final step we could ensure conformance. We saw a wide range of material size and eventually found trusted suppliers that sourced their material from excellent mills. In my experience steels from Imatra, Ovako, Corus, Ascometal, Ronane, Mitsui, Nippon have excellent cleanup. (sorry, very limited exposure to US steel). You'll find cheaper material but it is a hit and miss affair.

In the above example, it was a medium size run in a competitive manufacturing environment. It was important for us to have the raw bar stock as close to the finish diameter while giving acceptable rejects. If the job was one-off and no crack detection was available, I would have played it safe and used 70mm or 75mm bar stock.

There we are - a very long way of saying 'it depends'.

Lew

 

[Philrock]

I have old stock lists (in book form) from Jorgensen Steel (now EMJ Metals) and Ducommun. These books list what they call standard mill tolerances. The tolerances in the two books are identical, and whenever I ask a supplier for the tolerance on something I am ordering or specifying, the tolerance he gives me matches what's in my stock lists. This leads me to believe that standard mill tolerances have not changed in decades. Perhaps a supplier could tell you what his source of mill tolerance information is.

 

[christate]

Central Steel in Chicago publishes a catalog that has all of the info you request. Also get a copy of Machinery's Handbook.

 

[RedPen]

Depending on where you are located another stock list you may find useful is Ryerson Steel. Find them at

http://www.ryersontull.com

 

[ornerynorsk]

If you are looking for high volume material, have the mill manufacture to your requirement. For example, if you want approx .030 finish stock, have them cold roll to 2.530/2.540 or hot roll to 2.56/2.59. If you need additional allowance for straightness, heat treat, grind, etc, just add what you need. Many mills will roll to size for you.

 

[BillPSU]

Quazif
I think your looking for similar tolerances spelled out in A519 for tubing which gives suitable for honing/skiving sizes on the ID of tubing. I don't think that information has been compiled into a standard for OD sizes. The problem is requirements vary based on what the manufacturer is doing to the material. If the material is centerless ground or between center ground more stock would have to be given for the between center processed material versus the centerless material.

I think you need to document what you currently use for you processes and review the materials. Use this information as a starting point for new projects and if you have the time and the resources experiment with reducing stock allowances hopefully reducing costs. If there is no reductions in cost don't change the material. The additional material can help absorb process variablity.