Surface grinding finger break dies before heat-treat worth doing?

[keeena]

I made some finger brake dies out of 4140 and will be sending out to heat treat. Is there any benefit to surface grinding before sending to heat treat?

Either way: the dies will be left slightly oversized and I'll be grinding after the heat treatment to bring to final dimension and clean up oxidation.

 

[rwdenney]

I would think not. 1.) does a break really need that level of precision? 2.) heat treating is likely to cause some distortion anyway, and if it needs the precision of surface grinding, I would think one would do that after heat treating.

Rick "not an expert" Denney

 

[keeena]

Yes, was planning on grinding afterwards regardless. Grinding the dies isn't as much for precision as it is simply cleaning up oxidation/HT scale to make them look purdy.

 

[benmychree]

With an up-to-date heat treater, there should be little or no scaling of your parts, just some heat discoloration.

 

[keeena]

@benmychree - I hope that will be the case! When I spoke to the company it seemed a bit unclear what the finish would look like after HT. I'll get a better sense when I drop the parts off.

 

[benmychree]

The heat treater that I dealt with had furnaces with controlled atmosphere, and quenching was done within the atmosphere, there was no scaling.
When I did heat treating where I apprenticed, we packed the parts in crushed peach pit charcoal to eliminate scaling and decarburizing of the parts, that's the old - fashioned way.