Advantages/disadvantages of cast iron surface plate vs. granite

Spud

Diamond

Joined

Jan 12, 2006

Location

Brookfield, Wisconsin

• Dec 7, 2020

• #1

What are the reason to go for a cast iron surface plate over a granite one?

The Tesa, Starret and Mitutoyo digital height gauges at my tech school are on a granite plate. I don't think I have even seen a cast iron surface plate there.

 

H

Hillside Fab

Cast Iron

Joined

Nov 16, 2014

Location

Missouri

• Dec 7, 2020

• #2

I have a roll around CI one that I use for more of an "out in the shop" plate.

It's pretty tough, like a machine table would be. Also probably no more flat than your average machine table.

 

H

Hillside Fab

Cast Iron

Joined

Nov 16, 2014

Location

Missouri

• Dec 7, 2020

• #3

Cast Iron VS Granite Surface Plates.

 

Mud

Diamond

Joined

May 20, 2002

Location

South Central PA

• Dec 7, 2020

• #4

They are magnetic, for one.

 

O

Outtatramm

Plastic

Joined

Dec 7, 2020

• Dec 7, 2020

• #5

Cast iron pros: cheaper, magnetic, lighter weight, tappable, impact shock resistant.
Cast iron cons: magnetic, corrosion risk, thermal changes.

Granite pros: wear resistant, stable in wider temperature range.
Granite cons: heavy, more expensive.

 

T

TGTool

Titanium

Joined

Sep 22, 2006

Location

Stillwater, Oklahoma

• Dec 7, 2020

• #6

To the cast iron pros you should add:
Easier to tune up in the average shop than lapping granite.

 

Peter from Holland

Diamond

Joined

Jan 15, 2005

Location

The Netherlands

• Dec 8, 2020

• #7

If you have a scraped CI plate the biggest advantage is that
it is much better for blueing It holds the blue much better and touches better IMHO
Peter

 

rimcanyon

Diamond

Joined

Sep 28, 2002

Location

Salinas, CA USA

• Jan 5, 2021

• #8

TGTool said:

To the cast iron pros you should add:
Easier to tune up in the average shop than lapping granite.

Click to expand...

To the cast iron cons you should add:
More likely to need tune up in the avg. shop than granite plates.

 

T

TGTool

Titanium

Joined

Sep 22, 2006

Location

Stillwater, Oklahoma

• Jan 5, 2021

• #9

rimcanyon said:

To the cast iron cons you should add:
More likely to need tune up in the avg. shop than granite plates.

Click to expand...

That echoes the hide glue argument on musical instruments. Pro: Heat and moisture make it reversible facilitating repairs. Con: If the glue didn't fail so often you wouldn't need as many repairs.

 

M.B. Naegle

Diamond

Joined

Feb 7, 2011

Location

Conroe, TX USA

• Jan 6, 2021

• #10

The smaller granite plates seem to become pavers (junk) when they get out of spec. While the larger ones are worth having resurfaced. Smaller cast iron plates are economical to resurface, while the larger ones take so long that it's hard to put a price on the task.

Granite necessitates having pro's come to your shop to service them but you get certifiable work. Some guys do it themselves but IMO these cases seem to raise a red flag over the accuracy of the job. Iron's the opposite. I've yet to find a metrology lab that scrapes. They'll certify iron but only in the ways they do granite (CMM, repeatometer, autocoluminator, etc.), not by printing. Conversely, if you have a plate that was hand scraped by "Joe" to 40 PPI, by-golly that's a priceless piece of gauging equipment there.

They all have their place.

 

Toolmaker51

Cast Iron

Joined

Jan 13, 2009

Location

West MO

• Jan 7, 2021

• #11

Hillside Fab said:

I have a roll around CI one that I use for more of an "out in the shop" plate.

It's pretty tough, like a machine table would be. Also probably no more flat than your average machine table.

Click to expand...

Sssssssssh Henry Maudslay or Joseph Whitworth might hear.

Surface plate - Wikipedia