How to determine if your surface plate is out of tolerance.

This is a quick way to tell if your surface plate needs reworking.
https://www.youtube.com/watch?v=hui6pPZH36U

1. Where did you get that wild looking height gauge?

2. I think your claim goes like this:

a. We presume the plate was good sometime in the past, this is a "is it worn check" not part of making it to spec in the first place.

b. Measure the repeatability (what you are doing in the video) - in theory a surface plate could actually be a sphere of very large radius, and repeatability would always be good, even though it's not actually flat. But it's just not credible that a plate that started known good flat would wear in to have good repeatability everywhere by being a sphere.

And of course, you could do the height gauge drill when the plate was new, with say two different lengths of indicator reach, and record the answer....

I agree with the idea of often checking your inspection equipment by comparison methods. So I'm not dissenting the spirit of the post. However, I've always been taught that ammonia has no place near a granite surface plate because it will damage the surface.

Yet I've seen posts from both Don an Richard King in the past couple of weeks advocating the use of ammonia in conjuction with surface plates. So I'm confused. Have I been mislead all my career? Is ammonia harmless to granite or not? Is it ok to use Windex on my plates?

I would really like to know what others have to say.

Best Regards,
Bob

bryan_machine said:

1. Where did you get that wild looking height gauge?

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It's really comparator stand I think.

I have one that's the same style made by Verdict.

Nice quick explanation of relative method for routine "sanity check" of the surface plate. I think the commentary about this not being definitive is excellent, although this type of check can be very valuable if done often. The same thing can apply to more complex tools such as a CMM; get a standard of some sort and use it routinely as a double-check to see if there is anything different in the tool behavior.

Regarding the ammonia-based cleaner, I'd be interested in an evaluation of that cleaning agent. I doubt that there is any negative effect, but I'm not certain about the chemical interaction that might be at work. I will say I have used Windex as a cleaner previously with no observed issues, as well as isopropyl and methyl alcohols, and Starrett surface plate cleaner. They all did the job, but I am partial to the Starrett product. It really makes the surface work smoothly.

On the youtube page I posted the below comment, only to have it swiftly deleted. If I'm wrong or you simply disagree, please, I welcome a discussion.

This test is complete inconclusive and misleading. I fear that many of the viewers will immediately try this, and get false reading that will either convince them to unnecessary call for servicing, or convince them that a bad plate is up to the task.

The fault is that this method doesn’t take into account the overall tolerance to the repeat tolerance, and the fact that the perimeter inch of the plate dosen’t need to make a certification.

Example: that plate is about 18X24, and B grade, I’m assuming because it in the shop. And lets say that it meets the federal specification.

That means that the highest peak to the lowest valley is .0003 or smaller irrelevant to shape, concavity/convexity. And the repeat reading (the flatness within a 10 section) of 0.00011” throughout the plate. The purpose of the repeat reading is to ensure there isn’t a washboard profile on the plate, as a single curve is preferred over multiple.

Should the back leg of the indicator holder fall in a .0001 hole, the long are of the holder will double the reading. And should the far end be naturally .0003 higher. (All acceptable of a surface plate)
You could easily have half thousands of total indicated reading, on a certified plate. Add to that the rim may be low in excess of a thousands.

Conversely if you have a washboard surface with the highs and lows in excess .00011 and you happen to have the indicator reading off of correspondingly high spots(or hemisphere). You may have readings less then actual and may convince you not to call for an inspection when its actual desperately needed.

http://static1.squarespace.com/stat...37677518/FEDERAL+SPECIFICATION+GGG-P-463C.pdf

http://what-when-how.com/metrology/surface-plates-metrology/


Concerning the ammonia cleaner debate.
The real enemy of a surface plate is water, in the starrett catalogue the fine grain of their black plaits is advertised as having lower absorption of fluids. As water could aide in rusting gauges left on the plate. Ammonia itself evaporates at -28f so its dissolved in water, at room temperature the most that can be dissolved is 1/3 by weight. For Household cleaners I guaranty that the manufacturers are watering it down, and perhaps adding waxes to make floors and windows shiner.

So short of using the expensive dedicated cleaner, I advise to using any water free hydrocarbon. Acetone, methanol, Alcohol, kerosine, naphtha, mineral spirits, lacquer thiner, etc.

the best way to check a surface plate is a beveled straight edge of good quality (din 00). fast and you see whats going on.

Don't know much about surface plates, but do know a bit about the various alcohols and ammonia solutions:

• Any alcohol is likely to contain water because the hydroxyl (-OH) group that (as an example) converts ethane into ethyl alcohol or ethanol has a high affinity for water. That's why the best you can usually do at the drugstore is 90% isopropyl alcohol - the other 10% is water. Even if you go through the expense of obtaining virtually water-free (anhydrous) alcohol, it'll begin absorbing water vapor from the ambient air the instant it's applied to the surface.

• The major constituent in household ammonia is water.

Maybe that's why "waterless" and "without water" appear so many times in this: Surface Plate Cleaners

Where did I say this??? Put the link of here. I can't recall ever saying ammonia??

I have used Windex for several years and never had an issue. I just read Windex contains 5% ammonia...I never knew that...But I have never said to use ammonia. To me Windex does not smell like ammonia.

"Yet I've seen posts from both Don an Richard King in the past couple of weeks advocating the use of ammonia in conjuction with surface plates."

Don says in the beginning of the it is not the best method and if you were listening you would have heard that. Don Bailey has forgot more about machine shops then most people know. I go into shops and the plates have not be certified in years and I need to test my straight-edges that were qualified in my shop before traveling. I will clean the plate using Windex, Oh by the way I used to be a distributor for Tru-Stone before Starrett bought them. I have seen several brands of plate cleaner over the years from a paste, powder soap and hot water, seen people use Acetone, alcohol, etc. There is always someone who thinks he knows it all.

I have used 20 to 1 mix of industrial soap and water, never had an issue. After I washed a granite plate using a white towel until it wipes and no dirt sticks to the rag. I set my camel back on a number of locations and check the hinge or some call it the spin test. I use it in the areas where the spin or hinge test repeats. I have also set the straight edge on gage blocks or 123 blocks and measure with a surface gage the parallelism of the 2 surfaces, I have used a .0005 level to graph the plate. I get plates dirty with scraping blue so I am always cleaning plates. I use Windex or a good grade of class cleaner. Never a problem with rust or sticking!

Don shows in his several You Tube and in here helpful tips or tricks to the trade he uses and has used probably years before most of you were born. He is a successful business man and he is teaching us ways he has done it for years.

Some people like to bitch about just about everything. I for one want to thank Don Bailey for everything he does to help people in this trade. Rich

PS: Go to 4:10 into the following You Tube and see how we use a Plankator to test a plate.
https://www.youtube.com/watch?v=-4o4M2zBg6c

Plus you can look in my profile pictures and see how they are lapped and measured. Below is a surface plate lapper who I saw mix his diamond grit with water that he used to lap the plate. Plus use the Windex to wipe it clean when he was done.

Don Bailey said:

This is a quick way to tell if your surface plate needs reworking.
https://www.youtube.com/watch?v=hui6pPZH36U

Click to expand...

This thread has me a little puzzled. I watched the video but unless I missed it there is no mention of what tolerance the granite plate should have. I'm assuming most know that surface plates can be made and bought to several quality levels.

Surface plate - Wikipedia, the free encyclopedia

The surface plate in the video appears to be granite and I'd have to imagine very excessive hard use over a very long time to induce wear. All the granite surface plates I've cleaned and seen cleaned are done by using ordinary liquid soap the same as for hand washing dishes.

Things for me get even stranger when I see a related video where the same guy is using a micrometer with "feel" where it's obvious that the micrometer has a ratchet. That some choose to use a micrometer with "feel" is up to the user but it certainly isn't something I'd do if the micrometer had a ratchet and I'd certainly never recommend that "feel" is preferable to the ratchet. How does he think manufacturers test micrometers? I've seen it done by micrometer manufacturers and so far never seen "feel" used.

Richard King said:

Don shows in his several You Tube and in here helpful tips or tricks to the trade he uses and has used probably years before most of you were born. He is a successful business man and he is teaching us ways he has done it for years.

Some people like to bitch about just about everything.

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Then you won't like what I posted in #11 but I don't regard it as "bitching". I'm both curious and puzzled. If I met him I'd certainly ask him why he does as he does.

Looks good to me as a quick and dirty sanity check.

Gordon I was not talking about you. I wrote my post before your's.....and I don't read minds.
Don puts his mouth and actions, (time is money) on you tube and I have watched many of his You tube help posts. He spends time helping others with tips of the trade. Bottom line is He is teaching and should be thanked. I read yours and agreed with your dish-washing soap, as I have also used that just last year at American Babbitt where we could not find any Windex in their plant. Worked good. Relax.... :-) Rich

Richard King said:

Gordon I was not talking about you. I wrote my post before your's.....and I don't read minds.
Don puts his mouth and actions, (time is money) on you tube and I have watched many of his You tube help posts. He spends time helping others with tips of the trade. Bottom line is He is teaching and should be thanked. I read yours and agreed with your dish-washing soap, as I have also used that just last year at American Babbitt where we could not find any Windex in their plant. Worked good. Relax.... :-) Rich

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Richard, I'm very relaxed. Watching the couple of his videos I did just made me wonder for the reasons I wrote - especially the micrometer.

As to the granite surface plate it'd be interesting to know the "quality grade", what it gets used for and how old it is.

The two biggest granite plates I've bought were both 6feet x 4 feet and they were handled with care.

Richard
It's not a matter that I have lack respect for Don and his experience, quite the opposite, It's simply a matter of poor details and a few misleading videos he has made. Things like the micrometers as Gordon has pointed out,and the Lapping video where he has made every beginner mistake that the machinery's hand book tells you not to do.

For this primitive surface plate checking technique, I'm fully aware that he has proclaimed it not to be scientific. But for the concerns I listed in the above post, I fell that this technique should not be endorsed. Primarily because I fear that the date may be interpreted literally.

If say 10 people with the same surface plate do this check and get a readings ranging from .0001 to .001 of total indicated reading. Who do you tell to get thier plate professionally inspected or that their plate is fine? It's impossible to know with certainty. Do you otherwise trust this method only to a few thousands? If so there are a number of better techniques, precession spirit level, ground or scraped straight edge for example.


Concerning water on the surface plate. On the large plate at my former technical school there is a large stain in the shape of an indicator stand in the middle of the plate. The origin of the plate is unknown, whether it was in the rain once, or was repeatedly washed with water or water based cleaner. What is know is that the pours of the granite are filed with water, and if a steel item is left there for a prolonged period, it will be rusted in place and a hammer will be needed to get it loose. I will try to get a photo in the coming weak. Point being that companies like Starrett aren't just using a salesman's ploy to get you to buy a "waterless cleaner"

Alex McGilton said:

If say 10 people with the same surface plate do this check and get a readings ranging from .0001 to .001 of total indicated reading. Who do you tell to get thier plate professionally inspected or that their plate is fine? It's impossible to know with certainty.

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Alex,

What's missing is a standard against which to compare the current readings.

The simplest way to establish that standard is to use this test immediately after a plate has been trued and certified.
Record those readings, then compare future readings against them.

The critical factor here is to use exactly the same instruments and technique each time you check the plate.

There's nothing fundamentally "wrong" with the method Don presented.
It's meant to be a quick check to see if anything has changed. Obviously you need high-resolution tools.

- Leigh

GOOP, non-pumice, hand cleaner works great at getting surface plates show room clean if you will.
Rub it on, then rub it off. Kind of like waxing car.

Tom

To further your point, a small shop with multiple plates could zero that gauge on the best plate in the inspection room. Then cary it to all the plates on the shop floor, then bring it back to the inspection room to see if the assembly has moved at all.

Say someone has just purchased a new plate, uses the method illustrated and keeps a log book. They start with .0001 error and every year they notice an additional .0001 of error has gained. After what number of years should they call for an inspection? Where do you draw the line? By checking the GGG-P-463C specifications, a large shop grade plate will allow for several tenths of a thou of error. Do you take the reading literally? What multiplication factor do you use?

The impact of this method on viewers depends greatly on what kind of a shop they have. Professionals who have their surface plates inspected regularly as part of a ISO certification, won't bat an eye at this technique. Those who run a home shop, that got a used plate of unknown condition and not willing to pay for a certification immediately, are most likely to be mislead by this technique.

Going back to this thread, a lot of great insight was used for inspection of a surface plate after lapping it. Any the method involving levels or streaghtedges would be better suited in my my opinion.
http://www.practicalmachinist.com/vb/general/diy-surface-plate-lapping-266508/

67Cuda said:

GOOP, non-pumice, hand cleaner works great at getting surface plates show room clean if you will.
Rub it on, then rub it off. Kind of like waxing car.

Tom

Click to expand...

I think often it will depend very much on the surface plate material as to what should be used to clean.

I doubt very much if I'd clean granite and cast iron (to take just those two plate materials) the same way.

Those two materials have the advantage that, if anything gets dropped on the plate, worst case scenario is that it'll create a chip but not a "bump".