Grit

[PabloPicasso]

With sandpaper or wet n dry is the lower number coarser? i.e. 40 grit is rougher than 60?

 

[Concerto]

The number is the number of holes per square inch.

 

[han34]

With sandpaper or wet n dry is the lower number coarser? i.e. 40 grit is rougher than 60?

Yes, lower the number the coarser, so 1200 is very fine and 40 is very coarse

 

[PCUK]

With sandpaper or wet n dry is the lower number coarser? i.e. 40 grit is rougher than 60?

Think of it as the number of grains per inch. So the bigger the grains, the fewer there are and so the coarser the paper!

 

[andygc]

The number is the number of holes per square inch.

The lower the number, the larger the grit, the coarser the paper. I've never found a use for anything as coarse as 40! The definition is based on the number of lines per inch in the sieves that are used to grade the grit (not holes per square inch) Here's a conversion chart http://www.fine-tools.com/G10019.htm

 

[LittleSister]

Great stuff! :encouragement: Now I know something I didn't know I didn't know!

I knew which way the numbering went, but I didn't know why, or that it related to anything in particular. I've got a specialist repair job to tackle that involves working out the coarseness of some existing (embedded) grit, and this info will help me solve the problem.

 

[Marine Reflections]

Great stuff! :encouragement: Now I know something I didn't know I didn't know!

I knew which way the numbering went, but I didn't know why, or that it related to anything in particular. I've got a specialist repair job to tackle that involves working out the coarseness of some existing (embedded) grit, and this info will help me solve the problem.

Sounds interesting, what is it?
I'm in a nosey mood

 

[LittleSister]

Sounds interesting, what is it?
I'm in a nosey mood

Repairing some She-deck is the task. As you may know this was a 1970s proprietary imitation teak decking (as fitted to She yachts, Samphire yachts, and perhaps some others) with the 'planks' being a 'teak grain' effect printed tissue under (and over) clear gelcoat, while the black strips between the 'planks' are a slightly raised line of resin with grit set in it. It provides a fantastic non-slip surface. It also looked great when new (it seems from photos), but the looks don't last 30 years. While the faded 'planks' can be painted over, I have a few bits where the grippy grit/resin strip beweeen the planks has come away, and I want to replace these missing bits with grit of matching (or similar) coarseness and appearance (it's something black or grey that sparkles when it catches the light, if anyone has any suggestions) set in dark resin.

Thanks to this thread I now have a clue how to measure the coarseness of the resin (I may need to borrow a microscope from somewhere to do this, though).

 

[Concerto]

(it's something black or grey that sparkles when it catches the light, if anyone has any suggestions)

I would guess it might be carborundum, the grit used on wet and dry paper. That can look black, dark grey and slightly reflective. Small quantities can be purchased on ebay in the lapidary section as it is used for tumble stone polishing.

 

[LittleSister]

I would guess it might be carborundum, the grit used on wet and dry paper. That can look black, dark grey and slightly reflective. Small quantities can be purchased on ebay in the lapidary section as it is used for tumble stone polishing.

Thank you. Most helpful.