my new granite surface plate

[GOOFY063]

working at a funeral home has a few good perks, i was talking to the local monument company owner about a piece of broken or damaged granite for a surface plate he said come by sometime and we would what we could find and here it is 24x14x4 and the best part it was free ;D ;D ;D. thanks Henry & Henry

 

[Kmot]

Ha ha, cool! How much does that puppy weigh?

 

[b.lindsey]

Nice find. Can't beat that price per pound either :big:

Bill

 

[Metal Butcher]

I don't mean to sound like Mr.negative, but are grave stones ground and polished to the same degree of accuracy as 'official' surface plates are? Surface plates come in different grades.

Maybe I shouldn't be asking! Granite grave stones all over the world might start disappearing! oh:

-MB

 

[b.lindsey]

I would doubt they are MB, but but the same token, probably close enough for most home hobby needs.

Bill

 

[GOOFY063]

Kmot my back said a 1000 pounds but more like a 120 or so. MB I'm not sure about the accuracy but it has a good polished surface which should be more than good enough for my skills

 

[duckman]

Granite weighs about 160# per cubic foot simple just do the math. ;D

 

[rsendys]

I'm not sure about the accuracy

If you have a mill and dial indicator you can measure the quality of the surface this rock
Of course, to the nearest designated by the milling table ;D
It might be interesting and instructive to others - measuring boards cost a lot

 

[ksouers]

I've used a granite floor tile to good effect for several years. The lines I draw are just for reference anyway.

Look at the reflection of a florescent tube, if it appears straight then I think you're good to go Thm:
Any dishing of the surface would make the reflection appear to bow.

The reflection will probably have a slightly pebbly look to it, but the high spots should average out.

Not sure that measuring on the mill will be good enough. That would also assume that front and back are perfectly parallel.

The best way to measure it (cheaply) is with a Focault tester, used to measure the dishing on telescope mirrors. If you google around you will probably find several designs well within the skills of this group.

 

[Mainer]

My old mentor, the guy who ran the model shop at Morgan Industries in Worcester Ma and who built beautiful smooth-as-silk steam engine models, used a broken piece of stone storefront veneer for his surface plate for years. One time he said, "it falls off about 5 thou in the lower left corner, so I have to allow for that."

So...if Dan could do what he did with a piece of busted store front that was not uniformly flat, you ought to manage pretty well with a gravestone, although you may need to make allowances here and there.

Put an indicator on a base with a long-ish arm and sweep across the stone in various places to see what kind of variation you get.

 

[Layne]

Not a bad stone there, just a little small ;D Check out this one I had to move out of a small room at work this week. Weight is estimated at 7000lbs... that's a 6000lb chain hoist.

 

[dgjessing]

I use the cast iron top of my table saw for that sort of stuff. I don't know nor care how accurate it is - close enough for me ;D

 

[shred]

That's a big un... I remember the Boeing Surplus store (RIP) at Sea-Tac used to have a massive granite plate that looked like it could be a Pharoah's coffin lid. A foot thick, at least 4'x8' and an inspection tag attesting to it's flatness to some miniscule amount. It never moved all the years I went there

 

[Kmot]

Wouldn't a granite headstone be sliced by a big circular saw? And wouldn't the saw blade be nice and straight? So the slab of granite should be fairly flat, no? ???

I just purchased my first granite surface plate, 9x12x3, from Grizzly for $21 bucks. ;D

 

[GOOFY063]

sorry guys been busy at work lately, duckman if my math is right 124.32# ???
Mainer good ideal on the stand and dial, ill try that first afternoon i have off Thm:
Layne now that's a rock don't think my 2x4 and OSB table or my floor would hold that thing very well :big: :big: :big: