Surface plate support quick question

expressline99

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I just read in an excerpt from a early 1900's book that it's best to support your surface plate in a 3 point configuration. The part I read didn't go into any detail at all about what this was about. So is this valid or a typo? I'm sure it was referencing cast iron plates. (I think.)

Paul
 
Found this on Rock of Ages site.

SURFACE PLATE SUPPORT

In accordance to GGG-P-463c, Rock of Ages insures accurate readings of surface plates by supporting the plate properly on three support points. Three points are preferred and are located 1/5 the length and width from the ends and sides. Three supports are used because it is the only way to consistently support a surface plate object without the weight shifting from one leg to another. Any attempt to use more than 3 points may cause the plate to receive its support on various combinations of three points and the plate will settle differently and possibly deflect out of tolerance.

Rock of Ages provides various options for supporting surface plates:

  • stationary stands with leveling screws
  • stands with casters
  • stands with casters and leveling screws
All models with casters come with wheel locks as standard. Any working height can be specified to meet your application need.

- See more at: http://www.rockofages.com/en/industrial/products/surface-plates/#sthash.zSMXeVRf.dpuf
 
I just read in an excerpt from a early 1900's book that it's best to support your surface plate in a 3 point configuration. The part I read didn't go into any detail at all about what this was about. So is this valid or a typo? I'm sure it was referencing cast iron plates. (I think.)

Paul

A plane is defined by three points, therefore is much easier to level. Personally, I would think one would find a surface plate on casters less useful than one carefully leveled and stable.
 
A plane is defined by three points, therefore is much easier to level. Personally, I would think one would find a surface plate on casters less useful than one carefully leveled and stable.

Given the weight and it's setup location, a surface plate on casters may expedite shop projects. Level isn't the primary purpose of a surface plate, although having one set up in the level position seems to jump out as important. My concern would be the possibility of it getting tipped over and damaged.
 
Given the weight and it's setup location, a surface plate on casters may expedite shop projects. Level isn't the primary purpose of a surface plate, although having one set up in the level position seems to jump out as important. My concern would be the possibility of it getting tipped over and damaged.

Yeah, in my downsized shop, I'm looking at casters for a LOT of things, but I'm going to arrange them such that I can have a hardened point leveling the [whatever] against the floor.
 
Yeah, in my downsized shop, I'm looking at casters for a LOT of things, but I'm going to arrange them such that I can have a hardened point leveling the [whatever] against the floor.

In many of the carts and movable frames I've fabricated I like the foot operated brake that has about 3/4" of travel to use on the caster side of the table.
 
So is there a possibility of tipping on a 3 point stand? I'm considering a 24 x 24 plate. Probably the heaviest thing I would put on it would be 30-60 pound cross slides.
 
On a small surface plate I wouldn't worry about 3-point mounting. And I likewise wouldn't worry about it tipping, using a 3-point mount, as long as there was a full support surface just beneath the 3 points. Mine is 12" x 18" (IIRC) and sits on a rollaway cabinet.
 
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