Just bought a Collins Microflat 18 by 6 by 3. Anyone familiar with this piece?

[lowcountrycamo]

I bought a Collins Microflat parallel 18 by 6 by 3 here.

http://www.ebay.com/itm/201016158088?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

Maybe not a deal but cheaper than shars granite parallels. The unusual shape (to me) makes me wonder if it is also square at one end such as a granite knee would be. If not it is still useful to me but square would be a plus. I have done much searching and it seems this company is closed. At least it is usa made. When it comes I'll do my best to check but I have no real accurate square. Only "close to" squares. Anyone ever used or familiar with these? Thanks.

[TGTool]

I don't know what the squareness specs are for that but you can check it yourself to the limits of you measuring equipment without an outside reference. Squareness has the quality of being self-checking, so some parallels, some odds and ends and your best indicator should tell you how square it is.

[lowcountrycamo]

I do not follow. Without another square how would I check? I have indicators, mics, and a surface plate. I know if you have a square reference you can zero indicator on surface gage and check other parts for square. Thanks for your help.

[The Artful Bodger]

If you have just one square make two others to match against the one you have then compare those new ones against each other.

All you need to make a square is a plain surface, but you do end up with three squares!

[TGTool]

I don't know what the squareness specs are for that but you can check it yourself to the limits of you measuring equipment without an outside reference. Squareness has the quality of being self-checking, so some parallels, some odds and ends and your best indicator should tell you how square it is.

You'd use a setup something like this:



A surface gauge and indicator can be set up to touch at two points, bottom and top. Then with parallels, blocks or whatever organized to butt up against the square-to-be-checked at the same height as the indicator, bring the blocks and square to touch. Now using the indicator check the square and then the blocks (don't let them move). The indicator will show double the out of square error at that height.

[lowcountrycamo]

You'd use a setup something like this:



A surface gauge and indicator can be set up to touch at two points, bottom and top. Then with parallels, blocks or whatever organized to butt up against the square-to-be-checked at the same height as the indicator, bring the blocks and square to touch. Now using the indicator check the square and then the blocks (don't let them move). The indicator will show double the out of square error at that height.

TGTool, thank you for taking the time to create that diagram! Very generous of your time. And a very clever idea. I will do just that.

[boslab]

If you have just one square make two others to match against the one you have then compare those new ones against each other.

All you need to make a square is a plain surface, but you do end up with three squares!

Open to correction but was told we can thank mr Whitworth for that when doing the three surface exercise in a training centre!
Also turns out that you cannot see engineers blue on the earpeice of a black telephone, you only get to see the guy with the blue ear in the canteen at lunchtime, you can guess how i found that out
I soon learned to wipe the earpeice before answering the phone, but it also turns out that you cant see engineers blue on the rubber eyecups of a toolmakers microscope, you get to see the blue panda guy in the canteen at lunchtime, nobody will tell you, then you realise why the mirror is missing in the toilets!
Mark

[TGTool]

TGTool, thank you for taking the time to create that diagram! Very generous of your time. And a very clever idea. I will do just that.

The idea isn't new, but it's a useful concept to keep in mind. If you had something like a box square instead of the angle block it gets even easier. You check first to make sure that two sides are parallel (indicator work) then set the block with those two sides vertical and check it by swiveling 180 degrees.

I think Michael Ward describes this in his HSM series on scraping a year or two back but it's common to scrapers and machine tool rebuilders who need to have a good grasp of basic geometric principles. And it probably showed up in high school geometry but no one ever relates those boring proofs to the real world.