bead blasting

[jdm61]

i am going to be messing with some CPM 3V again and after my previous experience, I think that I want to get it as close to final dimensions and finish as I can before the blades go to Peters. Here are my questions. I know that a bead blasted finish may not be ideal for a non-stainless tool steel like 3V but it is an essential step if you want to apply a coating like Cerakote. Can the blasting be done before HT? Also, how fine of a belt finish do you need to go to before the grinder marks will not show through say a 120 grit AO or garnet blasted finish?

 

[leifjl]

I've only blasted knife blades after H.T.
Using glass beads as a medium, which is the only thing I have experience with, a 220 grit belt finish will come off with no trace quick and easy.
If your'e blasting as a preliminary treatment for the cerakote I'd think it should be done after H.T. You're gonna have to clean it up when you get it back from H.T. anyway.

 

[james terrio]

If your'e blasting as a preliminary treatment for the cerakote I'd think it should be done after H.T. You're gonna have to clean it up when you get it back from H.T. anyway.

That's my thoughts as well.

The only time I had any blades coated, my guy told me 220 was fine enough. They were already at 400, and he told me definitely don't bother going any higher than that.

 

[jdm61]

Cool. So 320 belt finish CLEAN with no leftover big scratches would be good before HT and then let my Cerakote guy do his normal bead blast?
My follow up question for you James is did you do the initial sharpening after coating and just take the coating off as you formed the edge or sharpen before and redo the final honing to get the Cerakote off?

 

[james terrio]

Cool. So 320 belt finish CLEAN with no leftover big scratches would be good before HT and then let my Cerakote guy do his normal bead blast?

Yup, makes sense to me. Surely the blasting will remove the minimal tempering oxides.

My follow up question for you James is did you do the initial sharpening after coating and just take the coating off as you formed the edge or sharpen before and redo the final honing to get the Cerakote off?

Yes. Flat edge before coating, normal sharpening procedure afterwards. I see no reason to sharpen it twice.