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Thread: Ebay "Precision Granite Square"
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23rd Aug 2019, 12:22 PM #1Most Valued Member
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Ebay "Precision Granite Square"
Hi all,
Been looking for a precision square on and off for a while now. I have a nice Moore & Wright Grade B but would like either a grade 0 or 00 for more accurate work. Also the M & W has a thin bevelled edge and so is very difficult to indicate off.
It won't be used all that often so I can't really justify mega bucks for it, hence why I still don't own one! I have noticed for some time that there are plenty of granite squares on ebay purporting to be grade 00 for very cheap (too cheap I suspect) so for around the $125 mark delivered I bought one of these:
https://www.ebay.com.au/itm/Cake-Pan...EAAOSwZrtcZUst
There are a number of these offered on eBay (all with the same model number HHIP-4901-2705) varying in price from what I paid all the way to around $400 in the UK.
A question for the brains trust out there, is there any way of testing it's squareness without the use of another master square? I have tested my M&W but its easier to do because the blade is parallel, you can test it by using a method similar to this.
https://www.youtube.com/watch?v=Qrxvs0b_ecs
Obviously that method is of little use with a triangle type square like a granite square.
Cheers,
SimonGirl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.
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23rd Aug 2019, 12:27 PM #2Most Valued Member
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I cannot answer your actual question. I do have a mahr 00 grade square to try it against. I can lend it to you and I'm not far away.
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23rd Aug 2019, 02:41 PM #3Most Valued Member
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Would it be possible to check against a cylinderical square. Set it up on your Granite Surface Plate, and slide a feeler gauge between the 2 at the top and the bottom, you should be able to feel the same amount of drag if it's right.
I believe gudgeon pins make good Cylinererical Gauges. For those that don't know, a Gudgeon Pin is what connects the piston to the conrod in an engine. If you went to an engine reconditioner, they'd probably give them to you, heavy truck ones are longer, as they have bigger pistons.
HTH
KrynTo grow old is mandatory, growing up is optional.
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23rd Aug 2019, 02:42 PM #4Most Valued Member
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Thanks Cask,
might be a good excuse for an afternoon get-together in the shed.
SimonGirl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.
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23rd Aug 2019, 02:47 PM #5Most Valued Member
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Thanks for the idea Kryn. Thing is, I still don't know how square the gudgeon pin is. I would rather come away with an actual figure rather than an idea.
Ultimately I would like to use this square as the reference square in my shed but if I really got no idea then it's a bit meaningless.
SimonGirl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.
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23rd Aug 2019, 03:41 PM #6Golden Member
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Here's a suggestion that seems to work in my head; take a straight edge and a parallel and set the parallel square to, and half-way along, the straight edge using your granite square, then move the square around to the other side of the parallel, set it say an inch away and measure the gap at top and bottom with an internal mic, bore gauge or similar. Could be done vertically with a cylindrical gauge on a surface plate, or horizontally if you can clamp the straight edge and parallel in position, say on your mill.
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23rd Aug 2019, 04:38 PM #7Gear expert in training
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If your surface plate is perfectly level, you could sit one of these against the vertical edge of the square and see what adjustment is needed to level the vial https://www.ebay.com.au/itm/MACHINIS...1/153451732884
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23rd Aug 2019, 05:47 PM #8Most Valued Member
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Yep, that should work in theory. I may be a bit clumbsy to make it work in a practical sense but worth a try. The difference between the upper and lower is twice the error of the square from top to bottom.
Hi Elan,
Only issue with that idea is is that it is now relying on the squareness of that item you linked to in eBay. I would be back to square one. No pun intended!
Edit: I think I misunderstood how that plumb gauge works. I'm still not sure but I'm intrigued. You may have something there but I'll have to think about it.
SimonGirl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.
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23rd Aug 2019, 07:26 PM #9Pink 10EE owner
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An autocollimator and a pentaprism will do it very accurately. Bring it over one weekend.
Gold, the colour of choice for the discerning person.
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23rd Aug 2019, 07:32 PM #10Diamond Member
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Do you know the technique to check the squareness of a block with a surface gauge and indicator? If the sides of the square are fairly flat and parallel you could use them to calibrate the indicator and then check the working surface.
I also have a square on the way now.
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23rd Aug 2019, 07:58 PM #11Most Valued Member
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Thanks RC. I'd love to come visit one day!
Simon
Sent from my SM-G970F using TapatalkGirl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.
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23rd Aug 2019, 07:59 PM #12Most Valued Member
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Hey snap,
What sort of square did you purchase?
Simon
Sent from my SM-G970F using TapatalkGirl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.
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23rd Aug 2019, 08:04 PM #13Most Valued Member
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Simon I think you don't have the equipment to test for squareness accurately, if the granite square had perfectly square corners then you might get a close idea by accurately measuring and then using pythagorus theorem.
If you use 2 granite squares on a plate and push them together with a strong light behind them you should see no light emanating from the other side.
If no light is apparent between them and if the hypotenuse of the same brand and model of squares is lapped then to measure them you could sit them one on top of the other, hypotenuse to hypotenuse to make a rectangle, sit them on a plate and run a dti along the top long side and then stand them up and run the DTI along the short side that is now at the top, then you could average the 2 figures, that is if you got any variation on the DTI
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23rd Aug 2019, 08:38 PM #14future machinist
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I bought a square from another Source. With The surface plate Group buy recently. It was slightly more expensive but not much more it's also a grade 00
BETTER TO HAVE TOOLS YOU DON'T NEED THAN TO NEED TOOLS YOU DON'T HAVE
Andre
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24th Aug 2019, 08:27 AM #15Golden Member
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I used my PMC Lonestar SquareMaster to check mine. If I recall, my square was well within the stated accuracy.
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