Safely Moving A Surface Plate

[jim18655]

I

I'll be honest and say I'm still doubting the single chunk of stone angle. The mating edges just don't jive with a ground shoulder. I'll take a real hard look tomorrow when the sun is nice and bright.
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The ledge might have been sawn and what you see as a glue joint might actually be the bottom of a saw kerf.

 

[4GSR]

Do believe that's a four ledge surface plate. Original accuracy was probably toolroom or lab grade. Been degraded over time from use. And if it was really resurfaced, which it could have been done so was brought up to a "B" grade accuracy.

 

[Tony Wells]

Maybe someone needed a plate with ledges and this was a way for them to get it.

 

[stupoty]

Hay if it's too big for you check the postage cost to the uk ,

Thats one piece of kit you shouldn't have to upgrade which is always good to know.

You could stick it on ebay and sell it to get a smaller one, they must be quite expensive that size.

Or maybe use the clasifieds hear to do a strait swap maybe? Their must be somone with a more compact one that wan't to get a bigger one.

Stuart

 

[j. vibert]

Hay if it's too big for you check the postage cost to the uk ,

~$470cdn depending on the delivery time

Thats one piece of kit you shouldn't have to upgrade which is always good to know.

Yes, that is the saving grace. I'll keep it around for the time being. I wish it was a tad more manageable, but hey where's the challenge in easy.

 

[extropic]

"inconsequential dimensions"? The problem with being lost is that we can be deep into it before we realize.

Rock of Ages and/or Collins can (could have?), no doubt, make (made) any special dimension surface plate that a customer would pay for. However, if you look at any listing of common SP sizes, 3" thick 24 x 36 is not a common thickness. Too thin to resist self weight, let alone live load of work piece(s) and metrology equipment. 4" thick is only common in import SPs. I would expect a 24 x 36 to be 6" thick. Based on the OP, I had suspicion that what you have is actually a 4 ledge surface plate. The concept of "ledges" is to allow easy clamping of work/fixtures to the SP. The ledges, at ≈3" thick, are stiff enough to support any reasonable load due to ≈3" overhang. The fact that your unit has labels from two manufacturers may be contrary evidence to my "4 ledge" theory", but not necessarily. The plate may have been manufactured by one and modified/reworked/calibrated by the other. The presence of some type of "epoxy" material isn't conclusive to me that you have two discreet plates bonded into an assembly.

In addition to whatever I might glean from seeing your piece in person, I would look for manufacturers serial numbers and call the to request info regarding what was built. I don't know if that info is retained, but I would call to find out.

If you have two discreet plates, I don't know what the perpetrator had in mind. The bottom of SPs are not commonly precision flats so now you would have a rough surface sitting on a precision surface? Reason? I can't imagine. The idea of bonding two thin plates together to create a stiffer unit would be news to me (but a good question to ask the manufacturers). Is that a valid manufacturing technique?

I'm guessing that your plate came from an industrial environment. Although bonding two discrete plates together is easy to understand in a hobby context, I bet it's very rare, or nonexistent (possible factory manufacturing technique not withstanding) in an industrial user environment related to precision metrology (maybe they just needed some ballast).

If you intend to end up with a precision surface plate, familiarize yourself with 'airy points' and implement a three point (small area elastomeric pads) mounting system. I would ask a manufacturer if the airy points are the same for a 4 ledge plate as they are for a no ledge plate (I don't think so).

Good luck.

On edit: I just saw numerous photos that were not posted (I missed?) when I read earlier. That is a 4 ledge plate. It isn't a bonded assembly. If you look at the "Rock of Ages" tag, it says RESURFACED. Conclusion; it's a Collins plate that was resurfaced/upgraded/calibrated by Rock of Ages. It's a nice piece. Make/buy a great stand for it (I see at least one elastomeric pad bonded at an airy point) and enjoy.

 

[j. vibert]

The problem with being lost is that we can be deep into it before we realize.

I like that, and it's extremely true.

I'm guessing that your plate came from an industrial environment.

The company which liquidated their assets produced audio recording medium, such as cd, dvd, vhs..... There were several surface plates that were on the block. I won the plate grouping so had the first choice of all the plates in the room. All of which were smaller in dimension then this Collins. This was my undoing as with the smaller perimeter dimensions come thinner plates. This Collins (because of the ledges) appeared to sitting on another lot. Uneducated mistake on my part. At any rate I only choose this Collins because of the 36" dimension. My hope is to dabble on some hand scraping in the foreseeable future. Figured the larger plate would be more useful in that regard.

On edit: I just saw numerous photos that were not posted (I missed?) when I read earlier. That is a 4 ledge plate. It isn't a bonded assembly. If you look at the "Rock of Ages" tag, it says RESURFACED. Conclusion; it's a Collins plate that was resurfaced/upgraded/calibrated by Rock of Ages. It's a nice piece. Make/buy a great stand for it (I see at least one elastomeric pad bonded at an airy point) and enjoy.

Nope you missed nothing. I braved the cold later in the day and snapped some more pics. I tend to be a video kind of guy so I didn't have stills available when I first posted the thread.

Although the plate is much beefy than I anticipated. I see no reason to flip it (so to speak) and start my search for a cheap/good reference surface again. The only real pain I'm suffering is the likelihood of moving from my current home within the next large handful of months. Makes lugging this plate downstairs and then most likely back up again in relatively short order an annoying venture.

 

[extropic]

At .00034" accuracy, per the Rock of Ages tag, it's about a grade "B" (.0004") plate. A "AA" Laboratory grade plate is .0001". The grade "B" may be suitable for your stated usage but it would be good to have a map of your plates surface. With a map, you can choose to work in the "best" area. Maybe that area is within .0001". Getting an accurate map will probably involve a profe$$ional calibration $ervice. There may be "DIY" mapping techniques but I'm not familiar.

I don't know what your needs and priorities are, but I would seriously consider making a wooden box, on a pallet, and store it until you move to the new house. If the storage needs to be outside, I would insulate the box (inside the box) with rigid foam sheet just to smooth out the temperature extremes. It's a rock after all.

There's always the option of offering it for sale at a profit and, later, buying a new Starrett Crystal Pink grade "AA" for about $2K delivered to your new home. Your wife (assumed) will like the color but what ever you do, never let her find out what it cost. You would also probably have quite a few new friends standing around, putting fingerprints all over it and making manly sounds (think Tim Allen, Tool Time).

Good Luck.

 

[j. vibert]

There's always the option of offering it for sale at a profit and, later, buying a new Starrett Crystal Pink grade "AA" for about $2K delivered to your new home. Your wife (assumed) will like the color but what ever you do, never let her find out what it cost. You would also probably have quite a few new friends standing around, putting fingerprints all over it and making manly sounds (think Tim Allen, Tool Time).

Good Luck.

Ah ha... You did miss something. "Cheap/good" are the only real criteria...lol. The first being mandatory, the second ballpark requirement. Pretending I managed to earn 75% of the cost of buying the Starrett plate by selling this Collins, I still wouldn't invest that much cash into a lab grade replacement. Just not in the cards for me. "Good" is good enough for this hobbyist.

...and unfortunately my close friends are still trying to figure out why I didn't just pick up an off cut from the local granite counter place....lol

 

[markknx]

Not sure if this will get it hot enough but seems like it could. If you can got the plates to a warm shed or garage, let them warm up to the temp. of the space this will take some time (like 12 hours). prop them up on their side in a way that protects both plates. Then aim a torpedo heater at them from say 5' (1.5 m) as the plates heat up slowly move the heater closer. The idea here is to slowly heat the plates so they don't crack, take your time. Not sure at what temp. the epoxy will give but once it does it sould also scrape off pretty easy at that temp. I think once the plates are hot to the touch would be a good time to try to gentely separate them.
Mark
PS I was going to say piano wire also till you changed to epoxy.

One more thought if heating does not work and you decide to destroy the small plate. A tile or masons table saw that can be set to cut as deep as the smaller plate is thick, could be used to take cuts every 1/2" or so. then these thin strips could be snapped off easy and safely. A concrete grinder could then be used to finish.