Checking Table Flatness

[dusty]

I know that this is NOT the intended application BUT could one of these be used to check table flatness by moving it around while watching the dial indicator.

http://www.igagingstore.com/category-s/1841.htm

[jsburger]

I know that this is NOT the intended application BUT could one of these be used to check table flatness by moving it around while watching the dial indicator.

http://www.igagingstore.com/category-s/1841.htm

Maybe. One would have to make sure the mounting arm for the dial indicator does not change position when moving the base/assembly. I am not sure how you could determine that it didn't move with absolute certainty. Hence the results would be questionable. We are talking only thousands for the most part.

[dusty]

I know that this is NOT the intended application BUT could one of these be used to check table flatness by moving it around while watching the dial indicator.

http://www.igagingstore.com/category-s/1841.htm

Maybe. One would have to make sure the mounting arm for the dial indicator does not change position when moving the base/assembly. I am not sure how you could determine that it didn't move with absolute certainty. Hence the results would be questionable. We are talking only thousands for the most part.

You are correct. If the mounting arm moves the reading is useless but if the mounting arm moves I doubt that it would only be thousandths.

Just thinking out load.

[reible]

Simple answer no.

They do make tools to do this but they are not in our price range.

If you know someone with at cnc (and large enough bed) and probe they could give you a good idea but they would have to make sure the surface is flat first..... easier said then done. And you would have to set some grid to test on other wise it could take hours for it to map the surface.

Simple way would be to look for light under a straight edge and then attempt to measure that with possible circular feeler gauges.... again you would only see low spots as measurements the high spots are another matter all together.

Ed

[jsburger]

I know that this is NOT the intended application BUT could one of these be used to check table flatness by moving it around while watching the dial indicator.

http://www.igagingstore.com/category-s/1841.htm

Maybe. One would have to make sure the mounting arm for the dial indicator does not change position when moving the base/assembly. I am not sure how you could determine that it didn't move with absolute certainty. Hence the results would be questionable. We are talking only thousands for the most part.

You are correct. If the mounting arm moves the reading is useless but if the mounting arm moves I doubt that it would only be thousandths.

Just thinking out load.

Probably true for most cases but maybe not all. My reference to thousandths was the flatness of the table not bumping the arm of the dial indicator.

I just think there is no way to guarantee the accuracy of the results.

[jsburger]

Simple answer no.

They do make tools to do this but they are not in our price range.

If you know someone with at cnc (and large enough bed) and probe they could give you a good idea but they would have to make sure the surface is flat first..... easier said then done. And you would have to set some grid to test on other wise it could take hours for it to map the surface.

Simple way would be to look for light under a straight edge and then attempt to measure that with possible circular feeler gauges.... again you would only see low spots as measurements the high spots are another matter all together.

Ed

I used to use a Zeiss CMM machine to measure the concentricity of T-38 aircraft generator main stators. You don't want to know the price. It was computer controlled and in a climate controlled room. The bed on the machine was a 4" thick piece of granite.

[dusty]

Simple answer no.

They do make tools to do this but they are not in our price range.

If you know someone with at cnc (and large enough bed) and probe they could give you a good idea but they would have to make sure the surface is flat first..... easier said then done. And you would have to set some grid to test on other wise it could take hours for it to map the surface.

Simple way would be to look for light under a straight edge and then attempt to measure that with possible circular feeler gauges.... again you would only see low spots as measurements the high spots are another matter all together.

Ed

I have a Starrett straight edge and I have checked the table using it and a set of feeler gauges. However, it leaves me wondering. I know the table is not flat but I would like to know with greater certainty where, how much and in what direction.

Though my tables are not perfectly flat, they all pass a test that was given to me by Shopsmith CS in response to a warranty question. Like a foul, I cannot locate the pass/fail criteria that was given to me. I have it somewhere, I just can not locate it.

[JPG]

Let's take a close look.

Using one area of an unknown flatness object to measure flatness of another area while relocating the initial area so as to measure other areas.

I totally agree with Ed.

Come on Dusty you of all people should know better.

[dusty]

Let's take a close look.

Using one area of an unknown flatness object to measure flatness of another area while relocating the initial area so as to measure other areas.

I totally agree with Ed.

Come on Dusty you of all people should know better.

You may be correct but I am going to pursue this some more anyhow.

I know from previous testing that my tables are not flat. I want to be able to quantify that. You can call it futile experimentation if you will but ....

Remember, this is woodworking equipment!

[dusty]

Let's take a close look.

Using one area of an unknown flatness object to measure flatness of another area while relocating the initial area so as to measure other areas.

I totally agree with Ed.

Come on Dusty you of all people should know better.

This sounds sorta like what one does when using this tool to determine the proper adjustment of the blades on the cutter head of the jointer. The tool rests on one area of the outfeed table while measuring the height of the blade. It is then moved to another location to measure the height of the blade in a different location.

The only real difference, as I see it, is that the integrity of the outfeed table (the reference surface) is assumed.

If the tool is calibrated on the outfeed table of the jointer and then moved to main table, as the tool is moved around the main table in indicates the variances that we all know are there. Those variances are now being quantified.