40 grit to block filler

[RosharonRooster]

Looking for thoughts and opinions on 40 grit to block filler...

 

[shine]

never! 80 is as rough as i go. 40 scratches are hell to get rid of.

 

[Chris_Hamilton]

40 years ago maybe. Not today. Filler sands much easier now and 80 is all you need.

 

[MJM]

If the filler is 2" thick, than by all means use 40 grit ......... when it gets down to 3/8" thick, use 80 grit.

 

[RosharonRooster]

That's what I kind of figured. I like 80 grit Sun might

 

[crashtech]

Well, this is interesting! I still use 40 to break the surface and remove spreader marks on larger fill areas, especially if it seems clear that another coat will be needed anyway. A box of 40 long lasts me a couple of years.

 

[elwood]

A lot depends on quality of filler. Less expensive generally doesn't spread as smooth as the higher priced stuff. So 40 might be needed to get it leveled out. YMMV.

 

[RosharonRooster]

Well, this is interesting! I still use 40 to break the surface and remove spreader marks on larger fill areas, especially if it seems clear that another coat will be needed anyway. A box of 40 long lasts me a couple of years.

How do you ensure the 40 grit are gone/filled and won't shrink back

 

[MJM]

How do you ensure the 40 grit are gone/filled and won't shrink back

Guide coat. 3M or Mirka powdered Guide coat. That's what I use.

 

[RosharonRooster]

Guide coat. 3M or Mirka powdered Guide coat. That's what I use.

I like Mirka over 3m. I have a jar of 3m and I can't wait til it runs out. I do like the 3m applicator though

 

[Chris_Hamilton]

Well, this is interesting! I still use 40 to break the surface and remove spreader marks on larger fill areas, especially if it seems clear that another coat will be needed anyway. A box of 40 long lasts me a couple of years.

Knowing you and your desire to limit materials, that seems like a waste buying a box of 40 to do what you are talking about.

 

[crashtech]

Knowing you and your desire to limit materials, that seems like a waste buying a box of 40 to do what you are talking about.

You are right. It could be that I am simply living in the past and haven't given up an obsolete habit.

How do you ensure the 40 grit are gone/filled and won't shrink back

You just have to keep its use fairly brief and for the purpose intended, to knock down spreader marks and do a bit of rough shaping. If a mistake is made and too rough of a scratch remains, it can be filled with polyester putty the same pinholes would be.

I am not advocating for the use of 40 grit, just sharing what I do as a contrast to the majority. New filler does sand much nicer and does possibly make 40 grit obsolete. Someday I will be obsolete too, and no one will buy 40 grit anymore when I am gone.

 

[OJ86]

I use 40 to knock down duraglass before skimming with filler. Ive had the same roll for like 3 years now.