Granite surface plates outside

[marka12161]

I have a 24 x 36 x 6 Rahn granite surface plate that inspected to grade A in the shop. I mounted it at a conveninet height for layout work and it's big enough to do double duty as an inspection plate for most machine components. However, it's a bit short for evaluating long straight edges. I really don't have room in the shop for a larger surface plate and was wondering what's the down side of keeping a granite plate outside. I understand the adverse effect of temperature changes on the work. Are there any show stoppers to keeping and using a surface plate outside if it is properly protected?

 

[TGTool]

Gravestone carvers on the lookout for fresh meat, err, stone.

And heck, use some imagination. Mount a larger surface plate vertically, against a wall, or even turn it into a wall! Now there's no worries of gravity sag when you check anything against it...

And particularly useful in qualifying your straightedge to do the vertical ways.

 

[metalmagpie]

I appreciate posts about surface plates. I would worry about the stand rusting and about algae growing on the plate. I'm about to put my plate outside for a few days while I work on the stand. But it's going to get lapped after that so any weirdness should come out in the wash so to speak.

metalmagpie

 

[lucky7]

I’m in a tight shop for space and found it useful to make a stand for my 30”x48” plate. Made it higher than manufactured stands partly at suggestion of experienced guys on PM for easier use, and also so I could store stuff on shelves under it. Oh, and it’s on rollers, but with pads welded into base to three point the stand when fussy.

Surface plate should be inside in climate control. From pics of your shop I think you can make it work.

I was at one point considering getting a 6’ TruStone granite straight edge or a rail component off a CMM for proving longer iron straight edges. Thought it would be convenient up against a wall. Too busy with other stuff now, but would jump on a longer granite straight edge if one came up at reasonable price.

L7

 

[steve-l]

I keep a 24 x 18 outside. They don't rust. Wash it and bring it inside to climatise when you need to. What problem?

 

[lucky7]

No worries about the granite other than needing a lot of time to acclimate to room temp. Esp if you live in a place like me where we get +35C and -35C. I don’t like to wait for days just to do a simple job….

I leave it inside. You do what works for you.

L7

 

[Conrad Hoffman]

It's already spent several million years outside, though it wasn't as precise back then.

 

[Richard King]

One of the students who took the Maryland Class at Tacahoe a few years ago bought a large surface plate and took it to a Grave Stone maker and they sliced it up to make granite straight-edges. You may want to get it cut in 1/2 as keep it inside the shop. If you wrap it in a tarp I would think you could store it outside on 3 points where it sets on a stand. You were going to host a class weren't you before Covid hit right up in NY? Winter in NY gets cold, so checking a straight-edge on a 30 below zero granite plate would change the Iron. Or setting in the sun would too. You could store it out-side and then bring it in when you need it. Let is sit inside for a day before using it.

 

[cyanidekid]

It's already spent several million years outside, though it wasn't as precise back then.

that would be several hundred million in most cases id think!

granite needs to be kept( mostly) dry for a stable precision surface. silicon dioxide, quartz, (the primary constituent) is soluble in water, fairly rapidly so in superheated water deep in the earth (thus geodes), but enough time and water will erode the surface in "atmospheric" conditions. as we are concerned with rather small amounts here, I wouldn't let it get rained on for sure. the non-homogeneous nature of it would only make things worse as well.

 

[Mark Rand]

Direct sunshine will make it hog to the extent that if you put a straightedge from the shop onto the sunny surface plate, it'll spin around on its centre. DAMHIKT!

The primary way for granite to weather is for feldspar to absorb water, expand, break the granite and turn into clay.

 

[marka12161]

I’m in a tight shop for space and found it useful to make a stand for my 30”x48” plate. Made it higher than manufactured stands partly at suggestion of experienced guys on PM for easier use, and also so I could store stuff on shelves under it. Oh, and it’s on rollers, but with pads welded into base to three point the stand when fussy.

Surface plate should be inside in climate control. From pics of your shop I think you can make it work.

I was at one point considering getting a 6’ TruStone granite straight edge or a rail component off a CMM for proving longer iron straight edges. Thought it would be convenient up against a wall. Too busy with other stuff now, but would jump on a longer granite straight edge if one came up at reasonable price.

L7

Thanks L7. Yes i could shoe-horn in a longish plate but it would be inconvenient as i use a rolling gantry quite frequently to move heavy stuff around. Too much stuff in the way makes it an obstacle course. My 2' x 3' plate is also on a stand with casters and shelves underneath. I made it so the top of the plate is 44 or 45" above the floor which is perfect for layout work. It sits on threee points as well.

My thinking is i would build what amounts to a small trailer with a removable cover. I could mount a largish plate on the trailer, store it outside until needed and pull it into the shop a couple of days before i need it. It would be an infrequent operation but adequate when required. i'm considering going down this road because large plates seem to have been going cheap on auctions.

 

[marka12161]

One of the students who took the Maryland Class at Tacahoe a few years ago bought a large surface plate and took it to a Grave Stone maker and they sliced it up to make granite straight-edges. You may want to get it cut in 1/2 as keep it inside the shop. If you wrap it in a tarp I would think you could store it outside on 3 points where it sets on a stand. You were going to host a class weren't you before Covid hit right up in NY? Winter in NY gets cold, so checking a straight-edge on a 30 below zero granite plate would change the Iron. Or setting in the sun would too. You could store it out-side and then bring it in when you need it. Let is sit inside for a day before using it.

thanks richard, my thoughts exactly

 

[ShannonSalinas]

I know my reply is a bit late, but I wanted to say that keeping a granite surface plate outside can have its challenges, but if you take proper precautions, it can work. However, if you ensure proper protection from direct sunlight, moisture, and extreme temperature variations, you can minimize these risks.

 

[dgfoster]

If you walk through a cemetary, you will see polished granite stones 75 years or more old that still shine like new. Though it is true that granite can weather (aided by algae, bacteria, fungi, and lichen) over geologic time intervals, it will not erode to any measurable degree in a hundred years. MIcrobial growth is a very important factor. So simply wiping it off occasionally probably would prevent any significant microbial growth. But my bet, based on grave markers and storefronts, would be that simply left out in the elements with no precautions made would result in zero measurable change in 50 or 100 years.

Heat equilibration, as has been pointed out several times previously, would be something to pay attention to and could take several days in extreme situations for a 6 inch plate.

Link to microbial affects on granite: Deterioration of Granite

Denis