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View Full Version : Surface plate stand requirements?



DICKEYBIRD
07-03-2009, 03:14 PM
I couldn't resist Enco's free shipping deal and bought a 12" x 18" granite surface plate and some other stuff. I never noticed the thing is THREE inches thick and weighs 72 pounds!

Originally, I was thinking I'd store under a workbench and just pull it out on the few occasions that I needed it. I don't think that's a good plan considering the condition of my aging back. I'm now planning to fab up a 36" stand on casters so it can be rolled out of the way when not in use. I also plan to make a plywood cap to cover/protect the s/plate and mount my buffer on top.

My question is about the construction of the mounting area for the s/plate. I plan to just weld up a rectangle of angle iron to cradle it with 4 legs, a storage shelf or 2 with 2 fixed casters and 2 swivel casters. Are there any special support or mounting considerations to keep in mind to help keep the thing flat?

Forrest Addy
07-03-2009, 03:31 PM
There are three points defined for support on granite surface plates speced in GGG-P-463c. If your import was inspected and certified on these points it would be a miracle. Since it's small and thick it probably doesn't matter how it's mounted so long as its convenient to use and is more or less level. I have one on a Sears roll around tool chest bonded to the top with silicone with a piece of outdoor carpet between the plate and the sheet metal. It checks out OK with the Federal differential level.

willmac
07-03-2009, 05:25 PM
It is true that for a small surface plate a uniform support such as a strong bench should be perfectly ok. However even cheap granite plates may have their Airy points marked on their underside; mine did. If you are a picky about this kind of thing then you could easily build a frame to hold the plate at a good working height supported at these points. See the image for one that I built a while back. The Airy supports are made from bolts with the heads machined flat This frame is designed to fit around a standard kitchen unit carcase, ideal for storing associated kit such as height gauges etc. Mine is bolted down to the floor and levelled fairly carefully, which can be useful. If you make a roll around setup then you need to make sure that it is really stable. A surface plate falling off would ruin your day and anything else in its way. If you want more detailed drawing, let me know

http://i122.photobucket.com/albums/o248/moorbrook1860/surfaceplateassembly2.jpg

reggie_obe
07-03-2009, 07:22 PM
Why not recess the plate into the bench top and have a sturdy cover that fits over it and protects it from debris? It can be ready for use and protected from damage.
Considering the prices I've seen USA made surface plates sell for at auction, why would anyone buy Chinese? And I don't mean 3x5 foot size. When is a bargain not a bargain??

DICKEYBIRD
07-03-2009, 07:51 PM
I love this place.:) Good suggestions & info plus I learned something. I started to ask: "Hey mister, what's an airy point?" but I Googled it and was fascinated to read all about it on Wikepedia.

I haven't turned mine over to see if the airy points are marked but it appears that one can calculate where they should be, assuming Wikipedia is correct.

Reggie, I was thinking of doing exactly as you suggest but I think I'd need for the plate to be above the table surface in case I was working with a long workpiece. I don't want to have the plate and it's protective cover sticking up on the otherwise flat worktable.

I'd much rather buy American but since I work at my "real" job 55 - 70 hrs/wk, I don't seem to find the time Mon/Fri to locate any good used stuff. I have found some really nice American made cutting tools though at a couple yard sales and was ecstatic to get them.

Glenn Wegman
07-03-2009, 08:42 PM
Here's the Fed Spec.

http://www.tru-stone.com/pdf/Fed%20Spec%20GGG-P-463c.pdf

DICKEYBIRD
07-03-2009, 09:09 PM
Thanks Forrest & Glenn! It's now saved to my Machining Reference Docs folder on the shop PC.:) Much more than I can comprehend or use right now but hey, you never know.

wierdscience
07-03-2009, 11:06 PM
My Starrett 2x3' sits on it's facotry stand atop three hockey pucks,Dunno if that's original to it,but they seem to be working fine.The stand is nothing but bent up 11ga plate and a few carrage bolts.It's got bolt holes in the bottom for casters too.