Subject: Surface Plate Ledges?

From: [email-masked] (gaas::fisher)
Date: 8 FEB 95 15:49:03

I am about to purchase my first surface plate.
I notice that some of them have ledges.

What is the purpose of the ledges?

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

---

From: [email-masked] (Newton9120)
Date: 9 Feb 1995 23:16:30 -0500

I have been calibrating and using surface plates for several years and the
only reason I can see for the ledges is to reduce the weight of the
surface plate or to allow clamping fixtures to the surface plate using "C"
clamps.  By the way, I just bought my first surface plate.  I got an 18" X
24" black granite toolroom grade (0.0002") surface plate from Enco for
$75.

Jeff Dean
[email-masked]

---

From: [email-masked]
Date: 9 Feb 1995 18:26:16 GMT

>---------------O---------------
The ledges are provided as a place where fixtures and instruments can be
clamped to the table. I see in "Handbook of Dimensional Measurement" that
these are required by Federal Specification GGG-P-463b for granite surface
plates, but that modern practice leans toward eliminating the ledges
and clamping things down with threaded sockets cemented into the surface
plate. Starrett also recommends against the work clamping ledges in favor
of T-slots and threaded inserts "for sustained accuracy and reliability". 

                      ...when I sit down to write
Don Holly             my intentions are always blameless however deplorable
                      the ultimate effect of the act may turn out to be.
                                           --Joseph Conrad