# Accuracy of using visual



## Koi (Feb 3, 2020)

Im currently doing an assignment for workshop class and im curious how accurate can light crack indicate .Im using a caliper's body to indicate uneveness and file it down.Apparently i brought my own equipment to school cuz the ones in the workshop are quite beat up the files are dead smooth and the try square rusting and im not bolting the down the vice as well but shouldnt be a problem since im doing delicate filing for now.


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## Koi (Feb 3, 2020)




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## Cadillac (Feb 3, 2020)

Depending how good your eyes are down to at least .001 or better.


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## Koi (Feb 3, 2020)

Cadillac said:


> Depending how good your eyes are down to at least .001 or better.


0.001 sounds unrealistic though is there any evidence to back it up .


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## ub27Rocks (Feb 3, 2020)

You can prove it to yourself by taking a piece of cigarette paper or cellophane, measuring its thickness. Then place the paper at one end between 2 straight items. Shine light from behind.


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## rwm (Feb 3, 2020)

I would believe .001. I want to be like the terminator so I have a digital caliper embedded in my eye.


Robert


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## C-Bag (Feb 3, 2020)

I would suggest investing in a good machinist square. You have to have at least one truly flat surface. My go to for quite a while was a Starrett 6" rule or blade from a Starrett 6" try square. I kept it in a case and it's original cardboard sleeve so it wouldn't get dinged up. It's great you are next to a window, good light is a necessity. I also avoid tilting a straight edge for checking light unless you try it opposite as it can be slightly bent and give you false readings. Small granite surface plates are fairly cheap and are invaluable for checking your work. The side of a caliper was never meant to be used as a true straight edge IMHO.

Problem for me is after roughing in I do better rubbing the work on the file held on a flat surface than holding the work in a vise and filing it. There is a reason the final step for true flatness is to lap. It's hard to file truly flat. Another truly necessary tool is a set of tool room stones to stone your blade/rule because the slightest ding that you can barely feel will cause all kinds of light between the blade and surface giving another false reading. It's very attainable to get to .001 with very careful attention. But to get beyond that is many times harder.


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## Cadillac (Feb 3, 2020)

Don bailey shows on surface grinding videos that checking against a know square one can see the light between the part and square will actual turn a blue when within tenths. I personally haven’t done but I trust his word and he does demonstrate in the videos check them out.


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## Koi (Feb 4, 2020)

C-Bag said:


> I would suggest investing in a good machinist square. You have to have at least one truly flat surface. My go to for quite a while was a Starrett 6" rule or blade from a Starrett 6" try square. I kept it in a case and it's original cardboard sleeve so it wouldn't get dinged up. It's great you are next to a window, good light is a necessity. I also avoid tilting a straight edge for checking light unless you try it opposite as it can be slightly bent and give you false readings. Small granite surface plates are fairly cheap and are invaluable for checking your work. The side of a caliper was never meant to be used as a true straight edge IMHO.
> 
> Problem for me is after roughing in I do better rubbing the work on the file held on a flat surface than holding the work in a vise and filing it. There is a reason the final step for true flatness is to lap. It's hard to file truly flat. Another truly necessary tool is a set of tool room stones to stone your blade/rule because the slightest ding that you can barely feel will cause all kinds of light between the blade and surface giving another false reading. It's very attainable to get to .001 with very careful attention. But to get beyond that is many times harder.


I ordered one few days ago and have to go get it tommorow afternoon .Im studying mechatronic for now in a polytechnic and we have workshop assignment fitting i guess not really expecting to do this there though but since i gout the equipments then i might as well just bring it to my dorm.(sounds kinda crazy.


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## Koi (Feb 4, 2020)

C-Bag said:


> I would suggest investing in a good machinist square. You have to have at least one truly flat surface. My go to for quite a while was a Starrett 6" rule or blade from a Starrett 6" try square. I kept it in a case and it's original cardboard sleeve so it wouldn't get dinged up. It's great you are next to a window, good light is a necessity. I also avoid tilting a straight edge for checking light unless you try it opposite as it can be slightly bent and give you false readings. Small granite surface plates are fairly cheap and are invaluable for checking your work. The side of a caliper was never meant to be used as a true straight edge IMHO.
> 
> Problem for me is after roughing in I do better rubbing the work on the file held on a flat surface than holding the work in a vise and filing it. There is a reason the final step for true flatness is to lap. It's hard to file truly flat. Another truly necessary tool is a set of tool room stones to stone your blade/rule because the slightest ding that you can barely feel will cause all kinds of light between the blade and surface giving another false reading. It's very attainable to get to .001 with very careful attention. But to get beyond that is many times harder.


the vernier is kinda a temporary solution i know it was never meant for the purpose but i didnt know i should not use the sharp edge as a way to see.


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## Mini Cooper S (Feb 4, 2020)

Using the corner of of your caliper is probably not a problem because the bar on a caliper should be straight but I have seen guys use the corner of a bar that was bowed, that won't give you a true reading!  All of my good squares and straight edges have beveled edges on them. I use a piece of .0005" Mylar as a test strip between the blade of my tool and the surface that I am checking.  The picture shows one of my good squares against one of my good angle plates with a .0005" Mylar shim between the two.  It is amazinghow much light comes through that .0005" gap!  Remember also that if you are checking a ground or shiny surface, the gap of light appears twice as wide as it actually is because of reflection.


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## C-Bag (Feb 4, 2020)

Koi said:


> I ordered one few days ago and have to go get it tommorow afternoon .Im studying mechatronic for now in a polytechnic and we have workshop assignment fitting i guess not really expecting to do this there though but since i gout the equipments then i might as well just bring it to my dorm.(sounds kinda crazy.


Another really handy thing is a toolmakers straight edge. It has a built in knife edge and is way stouter than a machinist square. I bought a antique B&S TSE and it is in perfect shape but talk about accurate! I'm am in no way any kind of expert but having dove down the precision rabbit hole a couple of times the things this old TSE revealed were brutal. You start using a knife edge and I was crazy in no time.


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## C-Bag (Feb 4, 2020)

Cadillac said:


> Don bailey shows on surface grinding videos that checking against a know square one can see the light between the part and square will actual turn a blue when within tenths. I personally haven’t done but I trust his word and he does demonstrate in the videos check them out.


Can you direct me to which episode on YouTube he mentions this? I didn't see one that mentioned this directly.


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## Koi (Feb 5, 2020)

Bought a kennedy 3 inch square for Rm130 should be somewhere 24 dollars.


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## darkzero (Feb 5, 2020)

C-Bag said:


> Another really handy thing is a toolmakers straight edge. It has a built in knife edge and is way stouter than a machinist square. I bought a antique B&S TSE and it is in perfect shape but talk about accurate! I'm am in no way any kind of expert but having dove down the precision rabbit hole a couple of times the things this old TSE revealed were brutal. You start using a knife edge and I was crazy in no time.






I have a couple of Mitutoyo ones. I don't use them often & I could live without them but I came across them cheap on ebay. Great to have around when needed.


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## C-Bag (Feb 5, 2020)

darkzero said:


> View attachment 312694
> 
> 
> I don't use them often & I could live without them but I came across them cheap on ebay. Great to have around when needed.
> ...


This describes most of what I have in my shop. And it's been quite a while since I dragged my TSE out but the right tool for the job. And in a hobby shop where you do it all instead of in a production shop where you are doing one thing it takes quite an array. Luckily there's eBay and being able to pick up deals on Old Dead Guy Tools. Bless them and may they rest in peace knowing another old guy appreciates what they passed on.


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## stuarth44 (Feb 5, 2020)

t


Koi said:


> View attachment 312488


here are ways n ways of filing, draw file in the start and yes you can file true, dead true, needs practice, n thas all I  have to say 'bout that)


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## Koi (Feb 6, 2020)

Also how much does a file remove on average for fine file and bastard cut file.


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## stupoty (Feb 6, 2020)

Cadillac said:


> Don bailey shows on surface grinding videos that checking against a know square one can see the light between the part and square will actual turn a blue when within tenths. I personally haven’t done but I trust his word and he does demonstrate in the videos check them out.



yeah if it's real close then optical will show you quite accurately as you start being smaller than the size of light.

red light is bigger than green and blue. hence the shift to blue.

You can see this also with chromatic aberration in lenses and the different focus mark on lenses for infra red.

"The  wavelength of green light is about 500 nanometers, or two thousandths of a millimeter. "






						That's About the Size of It | by Brian Koberlein
					

The writings of Brian Koberlein



					archive.briankoberlein.com
				






Stu


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## stupoty (Feb 6, 2020)




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## T Bredehoft (Feb 6, 2020)

Cadillac said:


> light between the part and square will actual turn a blue when within tenths.


Yeah, that's what I was taught, used it numerous times. You're then measuring the wavelength of the light. or some such.


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## Cadillac (Feb 6, 2020)

C-Bag said:


> Can you direct me to which episode on YouTube he mentions this? I didn't see one that mentioned this directly.



Sure the name of the video is how to square a part within .0001 on a SG. He shows all the ways to check about 3mins into the video.


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## stuarth44 (Feb 6, 2020)

Koi said:


> Also how much does a file remove on average for fine file and bastard cut file.


depends on how much weight you apply, use kero or wd40 on soft metals, but you,ve only got to see how many shavings come off when ,say, filing an axe to see how much, btw never file both ways pressure on the away stroke, files are not cheap, as with a hacksaw just pressure on way, lift the tool slightly on back stroke, trade schools are no more here, probs they did not teach these things, but they did 56 years back)


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## Mini Cooper S (Feb 6, 2020)

stuarth44 said:


> use kero or wd40 on soft metals, )



He means soft metals like aluminum, be careful with oil on steel. Some steels (I.E. 4140 and tool steels) can glaze over with oils, even oil from rubbing your fingers over the work, and your file will just slide over the surface. Not good for the life of the teeth on the file.


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## Koi (Feb 6, 2020)

Is there any numbers as a reference


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## darkzero (Feb 6, 2020)

Koi said:


> Also how much does a file remove on average for fine file and bastard cut file.



That's hard to say. As someone mentioned it depends on how many pounds the gorilla weighs who is doing the filing. Also depends on the quality of the file & the brand. Like one brand's fine file may not have the same pitch of teeth as another brand. It also depends on the file size. You can get a 6" & a 12" file, both in bastard cut or whatever, same brand, & the pitch of the teeth won't be exactly the same.


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## Cadillac (Feb 6, 2020)

Koi said:


> Is there any numbers as a reference



Count your strokes be aware of your technique and take measurements. Like said above their are way to many variables. If you wanna get anal weigh the filings after so many strokes.


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## Koi (Feb 7, 2020)

Mini Cooper S said:


> He means soft metals like aluminum, be careful with oil on steel. Some steels (I.E. 4140 and tool steels) can glaze over with oils, even oil from rubbing your fingers over the work, and your file will just slide over the surface. Not good for the life of the teeth on the file.


I remember looking at others forun stating oil will only cause file to glide and use chalk instead.


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## Koi (Feb 7, 2020)

stuarth44 said:


> t
> 
> here are ways n ways of filing, draw file in the start and yes you can file true, dead true, needs practice, n thas all I  have to say 'bout that)


i do it by bringing the surface quite flat with conventional technique by holding my file close to my torso and move my body instead and when im nearly flat i and square i will use the curved part of a needle file to file down the hump and its a bit of guess work and leaves frustrated  me every time when i dealt with a problem and another shows up.


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## Koi (Feb 7, 2020)

Does accidentally tapping an engineer square  affect its squareness like a small sharp tap on another piece of metal tube by accident.


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## stupoty (Feb 7, 2020)

Koi said:


> Does accidentally tapping an engineer square  affect its squareness like a small sharp tap on another piece of metal tube by accident.



maybe but probably not.

if you havn't raised a burr then the tap probably wasn't tooo hard, I find the easiest way to mess up a square is to accidentally put something heavy on the blade part and bend it 

(although I have a china made one that came wavy so I didn't have to wory so much  )


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## whitmore (Feb 7, 2020)

Koi said:


> Does accidentally tapping an engineer square  affect its squareness like a small sharp tap on another piece of metal tube by accident.


That depends on the heat treatment; if the square is properly stress-relieved (good ones are) the amount of energy that
is required to make it change shape is large (and won't result from a small tap); it will rebound elastically to its original
shape.

Old-time piano frames were cast, then left to weather for a few seasons or years, before any machining was attempted,
because a fresh casting could warp in subsequent weeks or months (and lose tune).   Nowadays, they get a heat/chill/heat/chill
cycle and are ready in a few days.


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## Koi (Feb 8, 2020)

stuarth44 said:


> depends on how much weight you apply, use kero or wd40 on soft metals, but you,ve only got to see how many shavings come off when ,say, filing an axe to see how much, btw never file both ways pressure on the away stroke, files are not cheap, as with a hacksaw just pressure on way, lift the tool slightly on back stroke, trade schools are no more here, probs they did not teach these things, but they did 56 years back)


Files and hacksaw has teeth that cuts like endmill right.Thats what i do from the first day i  own a file


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