Free machining aluminum / steel / stainless..

[Tom Szelag]

Hey guys. Looks like I'm going to be writing a 'Design for Machinability' guideline booklet for next year's Manufacturing Processes/Systems class in the Mech. Engineering department here.

 

I vaguely recall seeing some threads here talking about alternative grades of aluminum.. steel.. stainless steel.. that were much more friendly to machine (ie 6013, 6020, etc).

 

If you know of some material like that, jot it down here. I'd be very interested in hearing about it.

[Tom Szelag]

Or by the same token, what stuff to really avoid.

[DavidB]

7075 Al great to machine

[chris m]

+1 on the 7075

 

303 machines much better than 304

 

Low quality steels [1026, 1018] suck, regardless of how 'free machining' they are

[SLJ]

Been doing a lot of 7045 al lately. Not bad.

Years ago in another life, I used to turn a lot of 4140, up to 350 Brinel if I remember right. Worked well if you kept enough inserts. This was back in the KC-75 carbide grade days.

[Kevangel]

quote:

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303 machines much better than 304

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I built some special machines years ago and we were allowed to substitute 416?? SS for 300 series and it machined much better and was magnetic. Was not heat treated or it was the annealed grade... I have machined a bunch of the 400 series mold steels that were 32-38 RC and tough...not that...all I can remember..seems like I made some shafts out of 4140 pre-hard, that had the "L" designation for lead added and cut like butter...I remember as a younster the shop I worked at would substitute "stress proof" for cold roll steel 1018 and it cut like butter...

[PGW Steve]

We machine a pile of 416SS here. We use it in the receivers of the rifle and have it heat treated to a 36C before all the machining ops. The stuff is super nice to cut, easy on tooling and gives a great finish.

[within a thou]

I always hated machining Inconel X750. It is used in nuclear reators because of its higher melting points to withstand the heat of the reactor problem is it retains heat and gets so hot so fast it melts carbide

[bhayden10]

We also machine shafts out of 416 s.s. and it cuts great. We use it instead of 303 because it machines much faster. We don't heat treat them, and it will rust. Inconel 718 is tough, as is nickel 200. If anyone has any high speed (if its even possible) knowledge of nickel i would sure be interested.

[chris m]

I have run a couple of parts out of 416 and I agree that it is quite nice

 

Hard often cuts better than soft

[BernieT]

SST - 303 and 303se, good general purpose 300 series, very easy to machine.

 

Mild steel - B1113 and B11L13(ledloy), good general purpose, easy to machine, especially the Ledloy.

 

Aluminum - 2011, easiest to machine although any 2000 series or 7000 series machines very well.

Alum info

 

Good luck, your manual is a good idea for the designers.

[Kurt M]

Material selection is based upon a few criteria, including (comparative) material characteristics, availability, and price.

 

For example, for a thermoforming mold, billet alloy Aluminum is a good choice for thermoconductivity, durability for long runs, and machinablity for complex 3D cavity design.

 

6061-T6 is the industry standard.

 

6013 has a higher tensile strength,among other properties, allowing higher machining feedrates along with less polishing. It costs approx. $.15/lb. more than 6061, so the increased cost is justified in most cases.

 

7075 has a higher tensile strength than 6013, producing a better finish yet. Vac. drilling with #80 drills .060 deep is difficult now, breaking the bits easily. And the cost/lb. is higher than 6013.

 

For this application, 6013 is a good choice.