Nital or Temper Etch 1

[TMAX]

I was wondering if a part calls for Nital Etch on the drawing, but the part was not ground during the manufacturing process, should it still be Nital Etched or Tempesr Etch Inspected? The material is 4340 Steel, AMS6415. Thanks!

 

[Metalhead97]

TMAX,

In terms of drawing call outs, a nital etch and temper etch are the same thing; you are going to use nital to etch the material to inspect the temper. If the part wasn't ground then there is not a need to do a temper etch inspection because the part was not subjected to any post-tempering heating.

MH

 

[TMAX]

Thanks for your response MH.

Just to clarify, would machining the part after heat treat/tempering be considered a post tempering heating?

Would maching post heat treat/tempering be a reason to look for burning or over-heating due to the post machining?

Thanks, TMax

 

[Jaydenn]

Yes. You need to etch the part after any machining, unless otherwise specified in the drawing.

Nital etch has nothing to do with "grinding" per se; It is looking for any heat affected zones on a hardened component.
Grinding is simply a "high heat" process prone to burning, so etching is typically used to verify grinding ops.

These "burns" can be created by any type of manufacturing process. Milling, turning, drilling, polishing/deburring, etc.

It is wise to etch after machining a hard part.

J

NX 6.0.5.3