Picked up a granite surface plate tonight.

[240260280z]

Granite cutting board from Homesense @ $16 Dimensions ~18" X 12" X 1"

Good for finishing surfaces flat.

[cygnusx1]

Perfect for blueprinting the oil pump.

[LeonV]

Good idea!

[zKars]

Excellent sleuthing Blue!

You can either spray glue various grades of sand paper to it or use this system of abrasive particles as the lapping media like these

http://www.leevalley.com/en/wood/page.aspx?p=33017&cat=1,43072

I wonder just how flat that granite really is?

[LeonV]

I wonder just how flat that granite really is?

I'm thinking the same thing.

[240260280z]

Less than 1.5 thou. I have read:

Source:

http://www.model-engineer.co.uk/forums/postings.asp?th=28101

"I also have a granite plate from Tesco. I checked it with a GOOD straight edge (a new "best" ruler) and could not get a 1.5 thou feeler gauge under it at any point on the surface. I reckon that it is good to a thou over its surface - more than good enough for workshop use.

The smaller ones - down to "coaster" size may be useful for confined spaces!

Bizibilder"

[LeonV]

Less than 1.5 thou. I have read:

Source:

http://www.model-engineer.co.uk/forums/postings.asp?th=28101

"I also have a granite plate from Tesco. I checked it with a GOOD straight edge (a new "best" ruler) and could not get a 1.5 thou feeler gauge under it at any point on the surface. I reckon that it is good to a thou over its surface - more than good enough for workshop use.

The smaller ones - down to "coaster" size may be useful for confined spaces!

Bizibilder"

Cool, I'm thinking I could pick one up and check it with an indicator using the EDM table at work.

[240260280z]

I just tried this crude "zone" technique and got outlier +0.003" to -0.002" variations skating over the surface with a dial indicator....with most of it +/- 0.001"

http://www.ehow.com/how_7620766_calibrate-granite-surface-plate.html

Edited August 21, 2012 by Blue

[cygnusx1]

IMHO flat enough for 99% of automotive work.

[hls30.com]

Excellent sleuthing Blue!

You can either spray glue various grades of sand paper to it or use this system of abrasive particles as the lapping media like these

http://www.leevalley.com/en/wood/page.aspx?p=33017&cat=1,43072

I wonder just how flat that granite really is?

From the link in the above quote: "For your convenience, we also offer a safety-glass lapping plate (8-1/2" x 14" x 1/4") that is guaranteed to be flat. "

Looks like it runs less than $14!