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6061 Plate vs Bar stock for a round part

6061 Plate vs Bar stock for a round part

6061 Plate vs Bar stock for a round part

We are making a round part per the customer drawing. The drawing is old and calls for Al 6061 per AMS-QQ-A-250/11. Plate and Sheet. That spec is superseded. The new material is AMS 4025, 4026 or 4027.

The customer may allow a substitution but, before I ask, I have a few questions:

Since it is a round part (1/2 in thick by approx. 2 in dia.) We want to ask if we can use round bar stock. For example AMS-QQ-A-200/B. It has a higher yield strength than the 4027, at 52 Ksi vs 42.9 Ksi for the 4027. Starting with bar seems easier.

Does this seem like a reasonable request?

If we were to start with the plate, what would be the typical operations and machines to use to cut the plate into a circle prior to starting the lathe operations?

Thank you

RE: 6061 Plate vs Bar stock for a round part

If you have in house machining, I'd go ask the shop for their input.
We have a waterjet so I'd cut the plate on it then send it to the lathe.
Plasma works.
Take stock of what you have then form a plan.
Best regards, David

RE: 6061 Plate vs Bar stock for a round part

If working from bar works better for you, then one way to push that idea is that a part from bar will have uniform properties in all radial directions. A part cut from plate will have the L vs T property variations of plate.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: 6061 Plate vs Bar stock for a round part

Stronger is not necessarily better.

There may have been any number of valid technical reasons why the designer specified AMS-QQ-A-250/11. Plate and Sheet.

Or it may simply have been easy or convenient.

You are not doing yourself any favors at all by even suggesting an alternative. Your reply should be "The material specification AMS-QQ-A-250/11. Plate and Sheet has been cancelled by the issuing organization and no superseding standard has been published. Please provide a revised drawing with an active material specification cited."

Any other reply will only put you in a position to start answering questions that the designer should be answering, and that presumably are not in your scope as a fabricator.

RE: 6061 Plate vs Bar stock for a round part

Since this is essentially a Class I change, you must go back to the customer to determine whether the material substitution is allowed, per their design requirements

TTFN (ta ta for now)
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RE: 6061 Plate vs Bar stock for a round part

Kipmc77 (Aerospace)(OP)

round parts = round wrought stock. just saw the lengths to the correct size with roughing, good to go.
I never buy plate unless force to.

RE: 6061 Plate vs Bar stock for a round part

Thanks for all the responses.
@DavidStecker We might send it out for cutting by waterjet
@EdStainless We will bring that up in discussions
@IRStuff We submitted a formal request to use the QQ=A-200/8 material (was that a Calvin and Hobbes reference?)
@ mfgenggear The goal it to get formal approval from the customer. Just making the part from bar without approval would cause problems. We did submit a request. Waiting for a reply

RE: 6061 Plate vs Bar stock for a round part

turning rectangular or square parts is a pita, interrupted cut plays havoc with the lathe and tooling.
edit: and trying to chuck it. it takes a 4 jaw chuck, PITA

RE: 6061 Plate vs Bar stock for a round part


Obviously round bar offers possibility for high-volume NC-Turning/machining for good quality parts... 'fast' ... if OK'ed by the OEM. This all just makes me wonder 'why' the OEM [client] felt compelled to machine from [MF] plate that would be much-harder/more-costly to do?

OK, dumb old me is curious about s'more info..

What temper for the 6061 plate parts, IE: -O [SHT/AHT to -T?], -T4xx [AHT to -T6xx], -T6xx ???

6061 plate and sheet per AMS-QQ-A-250/11 = = -O, -T4, -T42, -T451, -T6, -T62, -T651
6061 plate and sheet per AMS4025 = -O... SHT/AHT required to -T4x or T6x [-O is terribly soft for any accurate machining process].
6061 plate and sheet per AMS4026 = -T4, -T451
6061 plate and sheet per AMS4027 = -T6, -T651

The 'customer drawing' could actually explain an awful-lot based on the embedded details, IE: what are required machined tolerances x.x [sloppy]... x.xx... x.xxx… or x.xxxx [+/-?????] [extreme high precision]?... What is the surface finish requirement, IE: 500-microinch RA [very rough machined finish] or 8-microinch RA [almost mirror-like finish]??

What is this part used for... ON THE NEXT HIGHER ASSY DRAWING??? Is it a stand-alone detail... installed-into a precision mechanical component... or is it welded-into an Assembly... and will the next higher Assy require finish-machining and heat treatment? Generally speaking it is 'best to weld -T4 with a weld-filler compatible for age-HT to -T6... unless full re-heat treatment is required.

Is grain orientation important?

Proposed EXTRUDED [round?] bar, AMS-QQ-A-200/8(NOT 'B')[now AMS4150, AMS1460, AMS4173] would NOT be my 1st choice.

For a SWAG like this... I would trend-toward round drawn/rolled bar per QQ-A-225/8 [now AMS4115, AMS4116, AMS4117 [etc] perhaps for better control of overall properties.

Just askin'...

Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
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RE: 6061 Plate vs Bar stock for a round part

Wil - the place where I worked a long time wanted to use on-hand stock materials; it may be when this part was designed they had a lot of plate.

One time I had a part, the front panel of a portable tester, that faced up and might be used as a stepping stool by a soldier. So it was the first and only time I had need for higher strength than the 6061-T6 we always used and called for 7075...

Fast forward a couple of weeks and get a call from the anodize shop - they'd set up for 7075 like the drawing called for and in seconds were like - unh, uhh.

Yup. Our in-house machine shop used the same on-hand stock they always did and hoped no one would notice. Sigh. Schedule won out over ensuring the part had a long life and boom - 6061 was on the f'n drawing.

RE: 6061 Plate vs Bar stock for a round part

Thank all you guys
@IRStuff, Tiggr of course
@WKTaylon, The drawing called for 6061 T6 per QQ-A-250/11. The cancelation notice allows AMS 4025, 4026 or 4027. The customers cross reference required 4027 and yes plate would be very hard to set up and machine. The part is a 2 inch support on a 2 in .030 thick Cone. Not much load. You are right AMS-QQ-A-200/8 not B. Tolerances are wide +/- .030. Grain direction not specified

Bottom line: AMS-QQ-A-200/8 seems like a reasonable request.

Lets see when the customer says.


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