Surface plate repair

DieselBoot · Sep 1, 2008

I bought a used and dirty Starrett pink granite plate, 2' x 3' x 6", off FleaBay and got it home to discover about 25% of the surface is bad. It's rough like it had acid spilled on it.

The defects are closely spaced in a corner of the plate and a dial indicator deflects about 0.005" as it passes over the worst of them.

Is the plate shot, or can it be filled with a compound of some kind and recertified? Thanks.

DieselBoot · Sep 1, 2008

Devcon?

I have some Devcon wear-resistant putty which is essentially a metal filled epoxy. Would that be a good way to repair this plate? Lapping it back to true is not a problem as I have access to a collimator and diamond lap. Have any of you ever repaired gouges in a surface plate? Thanks.

jalessi · Sep 1, 2008

Hi,

I believe that a margin of 1" around your surface plate is not required to be flat.

See attached Federal Guideline.

Jeff...

Holescreek · Sep 1, 2008

I have never heard of repairing a plate by any means. I have seen them lapped using diamond grit and smaller blocks of granite in order to smooth out the high spots but usually when the pits appear in the magnitude you describe they hit the dumpster. Make a wooden cover for the damaged area? -Mike

DieselBoot · Sep 1, 2008

I've heard of such repairs being done and some of the metrology web sites out there refer to the ability to make such repairs. I'm hoping to find details on what methods and materials are best. Really don't want to trash the plate for defects that seem so shallow, considering its 6" thickness but I'm also aware the possibility that it may not be fixable. A new plate of this kind runs about $800 plus shipping.

Jess10ee · Sep 1, 2008

Starrett Surface Plate Repair Shop

Wonder what the Starrett shop would charge to resurface and re-certify it?

May be a moot point since you have the collimater, etc., but I seem to vaguely recall that their repair shop was in the Southeast - maybe not all that far from you (maybe NC?).

Might be worth checking on.

I priced them doing some work on one of my plates, and IIRC, it seemed quite reasonable.

DieselBoot · Sep 2, 2008

Thanks, Jess. I found them in Duncan, SC, not too far from Macon. I've contacted them and await their reply.

mark thomas · Sep 3, 2008

If you learn of a "standard" filler, do let us know. My plate has lots of small surface dings in it, well over 5 thou deep. It does not affect the flatness or use at all, but it makes cleaning it a bit of a nuisance.

apestate · Sep 3, 2008

Starrett Crystal Pink is utterly fragile.

I had to quit a shop once. They bought a 12' by 5' Starrett Crystal Pink surface plate, Grade A, brand new. The thing was like 2-1/2' thick. It knocked my socks off during the job interview, so perfect!

As it turns out, it was just a work bench. People would eat lunch on it, come in and !#$%DROP&%^ off their parts for inspection, stain it with oil. I started getting anxious and started asking people to keep it down. I'd remind them that the Crystal Pink on the shop floor looks like ASS! It was like the straw that broke the camel's back, I said "screw this, I'm not working with tractor parts even if it is a nice shop."

I'd have it resurfaced. Not sure about the cost involved. If you find out, let me know... You can tell alot about a shop by their surface plate.

http://www.rockofages.com/precision/index.html

and Starrett's high cost services:

http://www.tru-stone.com/pages/faq.asp#question14

14) If my granite surface plate or inspection accessory is badly worn or pitted, can it be salvaged? Will Tru-Stone fix any brand plate?

A) Yes, but only at our factory. At our plant, we can restore almost any plate to 'like-new' condition, usually for less than half the cost of replacing it. Damaged edges can be cosmetically patched, deep grooves, nicks, and pits can be ground out, and the attached supports can be replaced. In addition, we can modify your plate to increase its versatility by adding solid or threaded steel inserts and cutting slots or clamping lips, per your specifications.

mark thomas · Sep 3, 2008

I just got a quote from Standridge at $445 for resurfacing (up to .125" removed) my 8 square foot AA plate.

If one was near Standridge, that's not a bad deal, perhaps 1/3 to 1/2 new.

mark thomas · Sep 4, 2008

mark thomas said:
I just got a quote from Standridge at $445 for resurfacing (up to .125" removed) my 8 square foot AA plate.

If one was near Standridge, that's not a bad deal, perhaps 1/3 to 1/2 new.

fwiw, I also got a quote new from Standridge. 24"x48":

AA $1049
A $856
B $739

plus $230 shipped.

So resurfacing makes sense if you're close, but not if you have to drive or ship the plate very far. The economics might be a little different depending on plate size of course.

howiesatwork · Sep 4, 2008

Mark, I know we used to use PW Calibrators to resurface plates we failed in calibration, but I'm not sure how current failures are done. I'll get with purchasing in the AM to see who our approved vendor is these days.

DieselBoot · Sep 4, 2008

Starrett responded to my request with a quote today. $635 to return the plate to a B grade. Shipping is extra, of course. A new plate is $887.

I somehow feel there must be a cheaper way. Before I toss this plate I will definitely attempt to fill the defects and lap it. There is not much to lose at this point, other than my labor.

rosie · Sep 4, 2008

I haven't read all of the reply's here so don't jump all over me. I have a metrology place within a couple hours of me. I asked them in the past the same question of fixing pecker tracks. They told me that one day they would fill the divits and the next day they would lap it back in.

I've been holding off due to lack of funds for such things. I plan to have it done but my plate is a 4'X8' DoAll.

Rosie

Holescreek · Sep 5, 2008

A quick google search for granite repair material found:
http://www.edisoncoatings.com/Stone/stone.html

might be worth a try depending on the material cost. Let us know how you make out.

mark thomas · Sep 5, 2008

DieselBoot said:
Starrett responded to my request with a quote today. $635 to return the plate to a B grade. Shipping is extra, of course. A new plate is $887.

I somehow feel there must be a cheaper way. Before I toss this plate I will definitely attempt to fill the defects and lap it. There is not much to lose at this point, other than my labor.

Interesting how much more expensive that is than quote I got. I am not accustomed to anything being more expensive in your neck of the woods than in CA.

Are you sure the defects matter? My plate has a zillion 5-25 thou divots that would make an indicator bounce wildly, but they don't affect using the plate. Most use is things like use of a height gage, the 3-4" base of which spans dozens of the "defects". It's the flatness of the high points that really matters. My plate was AA Lab grade NIST-traceable lapped and calibrated without any problem, despite it looking pretty crappy.

The only problem I have found with the all the nicks is that if allowed to collect dust and dirt, running a gage or something over the surface tends to pull the dust and dirt up and it can then get on the surface. So it's harder to keep clean than a perfectly smooth plate is (remember, smooth and flat are not the same thing)

Also, $887 seems pretty expensive for a new plate. Standridge price is $445 for the same plate.

I don't know about where you live, but used ones are not that hard to find here. Here's a nice Starrett pink AA with stand for $100:

http://losangeles.craigslist.org/lac/tls/822894415.html

opticsguru · Sep 5, 2008

DieselBoot said:
I bought a used and dirty Starrett pink granite plate, 2' x 3' x 6", off FleaBay and got it home to discover about 25% of the surface is bad. It's rough like it had acid spilled on it.

The defects are closely spaced in a corner of the plate and a dial indicator deflects about 0.005" as it passes over the worst of them.

Is the plate shot, or can it be filled with a compound of some kind and recertified? Thanks.

My advice is to send it out to get re-ground and calibrated. These plates should be calibrated every year for ISO certification. It sounds as though one trip will do for this plate.

DieselBoot · Sep 6, 2008

mark thomas - Wow. That Craigslist floored me. They are just giving that plate away. Never seen anything close to that in these woods and I've looked for a plate for months - they all seem to be in Ohio

I paid $250 for this plate and it was dirty, and without a stand. . .

A close acquaintance of mine owns a metrology shop nearby and will eventually have a look at this plate. I'll trust his judgment on the question of whether the defects matter, but you present a possibility I had not considered - that of the defects being inconsequential.

Holescreek - thanks for the link to Edison. I had missed them in my previous searches for a compound. What they are selling appears to be a stone-filled epoxy . . . exactly what I imagined would be suitable. I will investigate further.

All of you have been most helpful and I thank you.

DieselBoot · Sep 8, 2008

Photo of damaged plate

I took this in the very best light possible to highlight the defects. Consider this a 'before' photo, as my intention is to fill these pocks.

mark thomas · Sep 9, 2008

Interesting... I wonder how that happened. That's a lot worse than mine, and yours does look to me like it's going to affect reliable measurement in that corner.

I think if I were you I'd probably toss the thing and buy a new 24"x36" from Enco for $124.95. Hate to say it, but I think you got ripped off on that.

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