heat treating of S7

[wlwag]

I hope these questions qualify for the Mastercam Forum.

 

I am wanting to machine S-7 hardened to 54-56 Rc for a HSM/Hardmilling test. The size of the blank is 6" x 6" x 3/4". The size and depth of the cavity is 5" x 5" x 1/2" deep with a star shaped boss 3/8" tall from the bottom of the cavity.

 

My questions are: Should I rough/semi-finish the blank first before heat treating, then finish machining after heat treatment? Or, can I have the whole blank hardened, so I can hard machine to finished size.

 

As of right now I plan on using OSG exocarb end mills with air coolant/chip removal and a high performance holder.

 

I have no experience with tool steels or heat treating, so bear with me on these questions.

 

Thank you in advance for any help.

 

 

Ver 9.1 mill Level 3 with solids

[?Mark]

quote:

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Should I rough/semi-finish the blank first before heat treating, then finish machining after heat treatment?

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Yes.

Also make sure you leave I'd say about .020"+ stock on each surface.

 

For example 6" x 3/4 x 3/4 stock will grow on you up to .015" lenght wise and depending on ht company flatness could get warped considerably.

 

Hope it helps

 

Kkind regards, Mark

[?Mark]

Oh, and welcome to the best political/mastercam site on the web

 

Mark

[Hardmill]

All a matter of how you want to do it, both ways

are effective. Inserts or a lower end mills are

definetly cheaper if you do it before heat treat.

 

quote:

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with air coolant/chip removal

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Skip the coolant part, if you don't have the proper

air/oil mist system straight air would be best.

Cooling of any sort will only cause stress fractures

@ your cutting edge.

 

 

PEACE

[DavidB]

quote:

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As of right now I plan on using OSG exocarb end mills with air coolant/chip removal and a high performance holder.

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After HT don't use coolant when machining use air blast.

Recutting hardened swarf does no good for the tool.

 

[wlwag]

Thanks for the quick replies guys. I did plan on using air only for chip removal and cooling of the tool. Sorry for the confusion on that.