Advice on maintaining surface plate condition - Starrett crystal pink surface plate

apestate

Quite Involved in Discussions
Hello forum

The place I work for has a 9 x 4' Starrett crystal pink surface plate that is about 6 months old. It is grade A, and bought new. This giant monolith is starting to show signs of wear.

In your experience, are there any good ways to get machinists to take care of their surface plate? I try to explain to people that it should be treated as glass, and will even show them how easy it is to chip the pink granite on the sides. Does anything else work?

How much should I sweat over chips and dings? This pink granite has plenty of mica, which will probably migrate out of the plate whether or not it's mothered. Are chips and dings just part of work or strictly verboten?

We really don't even have a use for it. It gets used as a work bench and staging area more than as a surface plate.
 
Re: Advice on maintaining surface plate condition

atetsade said:
We really don't even have a use for it.
I think that may be the basic problem (Why did you get it, btw?). It would make it very hard to get the message across.

atetsade said:
It gets used as a work bench and staging area more than as a surface plate.
I hear you. That, I am afraid is a fate likley to befall any free surface around, and a surface plate has the added disadvantage of looking very sturdy... I have a feeling that many of us have been battling this problem.

I have one horror story: All of a sudden, just minutes after I had explained the do's and dont's of handling the surface plate to some coworkers, two managers decided to make an announcement. I suppose you guessed it? All of a sudden they both stood on the plate, using it as a stage :mg: :frust: The marks caused by their not to clean shoes are there to be seen to this day.:nope: I will not go into detail. but there was a bit of a discussion afterwards...:notme:

Anyway, what I used to do in addition to a lot of explaining was to put big signs on every side of the thing, saying something like "This is a piece of measuring equipment, not a staging area". Well, it helped a bit - sometimes... Nagging works too.

/Claes
 

apestate

Quite Involved in Discussions
Wow, thank you for the reply and amazing story Claes

Maybe management will consider a few ideas
  • Putting up a proper work bench for staging and inspection tool storage
  • Covering a portion of the plate for same, rotating cover periodically
I say we don't really have a use for it because most things are checked on the CMM. We don't have any precision layout tools aside from a twin-beam height stand on it, and 4 v-blocks that are "ok" but not calibrated.

The metrology knowledge is lacking to even attempt surface plate inspection techniques. Is there a good book on advanced surface plate inspection and layout, a classic, so to speak?

If anything, it would be nice to have backup in case of CMM failure.
 
atetsade said:
  • Putting up a proper work bench for staging and inspection tool storage
  • Covering a portion of the plate for same, rotating cover periodically
Sounds like good ideas.

atetsade said:
The metrology knowledge is lacking to even attempt surface plate inspection techniques. Is there a good book on advanced surface plate inspection and layout, a classic, so to speak?
I'm not sure (anyone else?). I would recommend reading up on the standard in question. I.e: Form and position tolerances and so on...

atetsade said:
If anything, it would be nice to have backup in case of CMM failure.
Clearly a good idea. I have ample experience of CMM's going on the blink, and a plate and even rather lmited measuring equipment (like mentioned above) will enable you to manually do nearly anything a CMM can do... It will just take a little longer, that's all. A prerequisite for that, of course, is training in metrology... That would be a good thing anyway: Running a CMM without knowledge of manual measuring is generally a poor idea. It is all to easy to produce street numbers instead of proper data...

/Claes
 

Jim Wynne

Leader
Admin
atetsade said:
Wow, thank you for the reply and amazing story Claes

Maybe management will consider a few ideas
  • Putting up a proper work bench for staging and inspection tool storage
  • Covering a portion of the plate for same, rotating cover periodically
I say we don't really have a use for it because most things are checked on the CMM. We don't have any precision layout tools aside from a twin-beam height stand on it, and 4 v-blocks that are "ok" but not calibrated.

The metrology knowledge is lacking to even attempt surface plate inspection techniques. Is there a good book on advanced surface plate inspection and layout, a classic, so to speak?

If anything, it would be nice to have backup in case of CMM failure.

Mechanical inspection can't be learned by reading a book; a good CMM tech should be able to figure out how to use a height gage on a surface plate. The Quality Technician's Handbook is a good written resource for reference purposes, though.

Insofar as protecting the surface plate, a few suggestions:
  • If it didn't come with a cover, buy one and keep it on the plate at all times when it's not being used.
  • If people, after being warned, keep putting stuff on it, wait until you see someone doing it, then beat the living snot out of him take whatever he put on it and put it on his desk, no matter how big, dirty, or heavy the thing is. Attach a note that says, "The 'table' you left this on is not a table. It's a precision measuring device. Please find somewhere else to put your stuff." Then sign someone else's name to it.:notme:
 
T

True Position

Good recommendation on 'The Quality Technician's Handbook', that was the textbook my surface plate layout class used, and I keep it near me to this day. The book is a little dated in what it shows, but is designed to cover the ASQ CQT exam Body of Knowledge.

http://www.amazon.com/gp/product/0130416797/102-4120062-0388148?v=glance&n=283155

While the advice everybody has given so far is correct, tell people to treat it well, cover it(if possible), one good thing about granite plates is that when they get dinged around, they remove a pocket of material but don't push up a edge/burr, if you wipe it off you generally have a smooth flat surface to work on.
 

Wes Bucey

Prophet of Profit
I had a much smaller surface plate for day-to-day use, but for it to be worth anything, it has to be in an area where it can be easily accessed and where jigs, drop gages, etc. can be easily moved on and off as well as to bring parts to and from the surface. This means you can't hide it in a lab or obscure corner where folks lose valuable time getting to and from the plate (and thus tend to "fudge" the readings rather than take the time and effort.)

I used to use the wonderful cover that came with it, but still had folks use the handy horizontal surface for temporary storage, then I had a brain wave when we had a cookout on the lawn adjacent to our parking lot!

One of the guys brought a specialty dish for everyone to try and he had this neat little mesh umbrella tent to place over the food dish to keep flies and stuff from settling on the food.

It turned out I only had to set one of these little mesh umbrellas on top of the cover as a visual signal that the surface underneath was to be protected from "pests." I suppose you could add signs to the tent or use folded cardboard tents as well. I just thought the "dainty" look of the mesh umbrella helped convey the "dainty" nature of the underlying surface, without beating folks over the head with signs.

Side notes:
  • Ensure the support table for the surface plate is strong enough for the plate PLUS work pieces, jigs, and instruments.
  • keep proper cleaning materials for the surface plate right at hand and encourage regular use.
  • easy and convenient storage for cover and umbrella is necessary to encourage recovering when finished with measurements and to make it easy to remove cover for working
 

gard2372

Quite Involved in Discussions
atetsade said:
Hello forum

The place I work for has a 9 x 4' Starrett crystal pink surface plate that is about 6 months old. It is grade A, and bought new. This giant monolith is starting to show signs of wear.

In your experience, are there any good ways to get machinists to take care of their surface plate? I try to explain to people that it should be treated as glass, and will even show them how easy it is to chip the pink granite on the sides. Does anything else work?

How much should I sweat over chips and dings? This pink granite has plenty of mica, which will probably migrate out of the plate whether or not it's mothered. Are chips and dings just part of work or strictly verboten?

We really don't even have a use for it. It gets used as a work bench and staging area more than as a surface plate.

We had a crystal pink plate at my last place. We constantly had parts coming out of grit blast (ALO2) Aluminum Oxide straight to the plate for dimension check. Despite the grit blast operators best efforts (also included in their work instructions prior to moving to inspection) they blew out and used rubber hammers covers etc... But to no avail the grit still got entrapped somewhat and a little would come out from time to time at the surface plate. We wiped off the grit and kept on trucking.

Even after a few years of this with noticable scratches on the plate, everytime the cal lab came out to inspect and rehone the plate it was just as servicable as the day we bought it.

This is a quote directly from the Starrett website.

http://www.starrett.com/pages/860_granite_surface_plates.cfm

"However, due to the quartz content of 32% in the Crystal Pink it will outlast the Black 5 to 1. The quartz content is the determining factor in the wearability of granite. Black granite is used primarily for its load bearing capabilities. With any specific weight the Black will be thinner than the “Crystal Pink” because it is literally just a piece of “rock” with no particular mineral content. Whereas, the quartz content of the Crystal Pink permits the instruments to slide much easier without any risk of wearing the plate."
 

Wesley Richardson

Wes R
Trusted Information Resource
gard2372 said:
We had a crystal pink plate at my last place. We constantly had parts coming out of grit blast (ALO2) Aluminum Oxide straight to the plate for dimension check.

Hi Gard2372,

Most likely the aluminum oxide was AL_2_O_3

Wes R.
 
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