Is this surface plate any good?

Gentelmen,

I'm looking for a surface plate for my home shop. I have to scrape a couple of machines and I also need to check flatness of the parts that I machine.

I'm targeting for 36x24 size, but my eyes were caught by this lot:

Granite Table 48” x 3” x 4” Surface Plate Inspection Isolation on Cart | eBay

It's large, close to my home, reasonably priced and comes with the stand on casters just as I need. The only issue is a big cut off in the middle and a bunch of threaded holes.

Brand is unknown and so is accuracy.

Is it worth buying?

Thanks!

No.




........

I'm with Larry.

Larry Dickman said:

No.

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Thank you for the reply!

I would appreciate if you share the context, that was behind this conclusion, so I know what to look at next time.

A surface plate gains it's utility when scraping by being a nominally "perfect" flat reference, and its smoothness allows for uniform "printing" of the spotting ink to the object being scraped.

When the surface plate itself cannot be proven flat, or has interrupting features like the slot and holes, it takes away the chance to be that flat reference. And ideally the plate is thick enough to maintain it's shape under additional load (the object placed on it), and be supported in the ideal locations underneath to minimize distortion from its own weight and whatever's on it.

This plate fails on all fronts - no idea of flatness, supported on the edges, too thin, slots and holes, etc. Find another plate, there's lots out there.

What Milland sais.

That plate looks a lot like those surplused around here by a local university. They use them for various kinds of lab research requiring mass, and flatness often modified, whatever it takes. Once the research is done they are sold for almost nothing. Accuracy is anybodies guess.

Best to buy new in that size range. Sometimes good used ones can be had at machine shop liquidations. Keep in mind when looking that the plates require supports according to how supported during manufacturer. Often on three supports. A stand made for the plate will reflect those support requirements.

for what it's worth, i bought a 2' x 3' x 6" surface plate for $50.00 and a quote to resurface it for $170.00. The guy will come to my shop.

marka12161 said:

for what it's worth, i bought a 2' x 3' x 6" surface plate for $50.00 and a quote to resurface it for $170.00. The guy will come to my shop.

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You must not be living in California. Here they will charge $170 only for picking up the phone if I call.