320 onDA sander questions

[Tony1968]

I laid down a second round of hi build on trunk lid after knocking it down with 220 on flat blocks. I reduced the primer a little to get less peal and it really came out nicely. More like an eggshell texture when dry. So I threw 320 on my DA sander and just did a little section to see how it goes since I've never done it. It's really smooth. My question is when I go to 400 grit, does blocking achieve the same as using a DA ? I just want to make sure no sand scratches reveal themselves after all is done. BTW the single stage urethane I'm using says 400 grit as last step before sealer and paint.
This pic is before she flowed out and dried. Much less peal after a few hours.

 

[melloelky]

I laid down a second round of hi build on trunk lid after knocking it down with 220 on flat blocks. I reduced the primer a little to get less peal and it really came out nicely. More like an eggshell texture when dry. So I threw 320 on my DA sander and just did a little section to see how it goes since I've never done it. It's really smooth. My question is when I go to 400 grit, does blocking achieve the same as using a DA ? I just want to make sure no sand scratches reveal themselves after all is done. BTW the single stage urethane I'm using says 400 grit as last step before sealer and paint.
This pic is before she flowed out and dried. Much less peal after a few hours. View attachment 202074

yes and no,the da will result in a smoother finish but it won't be as flat as if blocked.the da results in a smoother finish because its a small random/orbital pattern vs the blocked that's more of a straight lines
you're more like to have a bit of choppy look with the da because its motion and it'soperatingin a small ar a area at a time etc.after blocking I've da' it with a finer finish WITH an interface pad on the da.if I finished blocking with 320 id go 320 or 400 to get rid of those remaining block scratches.an inner face pad is a good investment,it softens the da on the surface of you will.and yes this is the short answer😄

 

[Tony1968]

yes and no,the da will result in a smoother finish but it won't be as flat as if blocked.the da results in a smoother finish because its a small random/orbital pattern vs the blocked that's more of a straight lines
you're more like to have a bit of choppy look with the da because its motion and it'soperatingin a small ar a area at a time etc.after blocking I've da' it with a finer finish WITH an interface pad on the da.if I finished blocking with 320 id go 320 or 400 to get rid of those remaining block scratches.an inner face pad is a good investment,it softens the da on the surface of you will.and yes this is the short answer😄

Understand. I'll finish da with 320 then block with 400. Don't want to risk choppy waves. I will get an interface pad and maybe I'll go over it lightly.

 

[08Malibu]

Understand. I'll finish da with 320 then block with 400. Don't want to risk choppy waves. I will get an interface pad and maybe I'll go over it lightly.

I think you misunderstood. Block 320, then 400 with DA and interface pad. That way you’re only using the da for scratch refinement, not shaping.

 

[Tony1968]

I think you misunderstood. Block 320, then 400 with DA and interface pad. That way you’re only using the da for scratch refinement, not shaping.

I misunderstood.. story of my life 🙃
I'll Block the rest in 320 and try 400 with the pad. Thanks