How to Accurately Inspect a Flat Surface

[@davidrahn9903]

Hey Joe! I wanted to say thank you before I'm even a full minute into this video. I'm a second semester machine tool student at a technical college and last semester in my blueprint reading course, and my general machining theory course we had not one, not two, not three, but four discussion about this very topic. After spending nearly 4 hours on the subject there was still one of my classmates that didn't understand the concept. I'm gonna send him this and hope it helps him. Thanks a ton Joe!

[@joepie221]

Excellent. Good luck with your schooling.

[@markwatson9816]

Joe, your videos are great, focused, and excellently presented. Each one is like a great lesson in shop class. Thanks for taking the time and effort to do them.

[@tobydulanski9480]

I always check the granite block for high and low spots first. Then the post heights, then the part. Flatness can also be checked from the surface you are checking to itself providing the part is big enough. Thanks for showing this Joe.👍👍👍

[@Sketch1994]

That's the right way to inspect for flatness, but let me add that with some math you don't need a surface plate, or precision stands. Just a fixed route for the dial so it travels on the same surface. If you plot the two measurments at different point you can substract one equation out of the other which eliminates systematic errors and you are left with the surface topology of the part. It's called a reversal method and it's the basis of precision metrology!

[@brucebellows7772]

Great instruction Joe. I'm glad you mentioned the 1-2-3 blocks towards the end. I've seen guys use chrome inspection balls to support their work with the ball sitting in the hole of a block, but that would require and accurate chamfer of the holes on the block so that the tops of the balls are of a uniform height. Your towers are the thing to have.

[@rubarb0406]

Joe, I have two plate glass telescope mirror blanks that are 25" in diameter. They will be used to construct a binocular reflecting telescope. Each blank is a meniscus (contact lens) shape. As one goes through progressively finer grits it becomes necessary to grind down the face of the edges. This is done to avoid spalling of the glass. I have been struggling with how to determine if the edge bevel is consistent (relative to chords) of the sphere curve on the blanks. The method you have shown using the towers and indicating off the bottom of the workpiece is inspirational. Thanks for sharing! My surface plate is barely large enough to pull this off.

[@nevetslleksah]

Gordon Brown - sound like a neat project and perhaps you need a larger surface plate?

[@rubarb0406]

Joe inspired my approach. One of these days I expect to see him wearing a pointy hat and doing his presentation from a corner of the room . . .

[@sinkosav]

Joe,you are the best teacher by far on you tube.....learn from you so much,knowledge you poses is amazing,real pro ...Mr Pete aka Tubalcain cant call him even teacher comparing to you and he have so many subscribers....regards from Croatia

[@joepie221]

Thank you for the compliment. Regards from Austin Texas USA

[@thefixerman1]

Always enjoy watching your channel, learn something new and useful every time, thanks.

[@mrc1539]

Thanks for the tip, I appreciate you videos showing us hobby or wanna be machinists that we can do things without buying high dollar equipment . Your videos are first class in my book !

[@jjhart59]

Ive been in quality 25+ years and this IS the correct way to check flatness, but ive seen a lot of people do it wrong....lol

[@joepie221]

I appreciate the support.

[@ericrichards5862]

Hi Joe, Nice technique I have used 3 jack stands with ball bearings on the center post then I set 0 above each stand by adjusting the jack screw then check the rest of the surface. Thanks again

[@reddogrg]

Eric Richards I've done the same adjust to zero on top of each jack and sweep the top surface.

[@ophirb25]

As usual great simple and useful idea. Thanks.

[@xxxyyy7252]

This is another way: kzbin.info/www/bejne/nF6lnWBoebmckMk

[@krishansikarwar1448]

Nice video Joe...A lot of people get confuse b/w flatness and parallelism during checking

[@joepie221]

Agreed

[@mr1enrollment]

Joe and idea: consider ending your videos with a teaser question which we can think about until you reveal the next video. Doing so would create a game of intrigue, and who could argue with that?

[@ignaciocastaneda5777]

Just starting in quality, this is a great video. Thank you for sharing your knowledge!

[@joepie221]

Glad you enjoyed it!

[@johndn9238]

Very good - three points define a plane, so yes, as long as the jacks are the same height, this is a nice practical way that I can apply to checking a frame I've made. Thanks very much.

[@maxcnc777]

Thanks Joe. I have a few sets of these myself. Always handy.

[@barrygerbracht5077]

Interesting idea to measure the underside. How would you go about making the towers if you didn't have a surface grinder? I assume you could turn the bottom with a cup shape so it only registers on the outside and then lightly lap them on the surface plate, but how to make the top perfectly square to the base. Or do you want it ball shaped?

[@PeteBrubaker]

I think I'm going to make some of these. I'm going to try using adhesive to hold small bearing balls in sockets for the points. Then see how close I can get the lengths using a collet stop. I also think you're right on the money with relieving the center and lapping them to final dimension. If the ball bearing and epoxy don't work out, I'll probably order a truncated ball with a blind hole from bal-tec. They make some fantastic and affordable kinematic components.

[@joepie221]

I don't know if my camera angle allowed for seeing it, but the center of the bases of those pins is relieved. Without a surface grinder, trial and error cutting would be the only way. I too like the ball bearing top concept, but remember, less surface area is good, but if it wears, the error would come on pretty quick. I still like the idea, but I'd be sure to use carbide balls.

[@nevetslleksah]

Joe Pieczynski - relieving the base end would be a good idea. But unless I missed it, I saw a center hole in the base of your towers, but did not see a relief. At about 3:04 in the video you show the bottom of the towers. Great work and thanks for the inspiration, I am going to make myself a set.

[@duckslayer11000]

Another priceless lesson taught. Thank you!

[@springwoodcottage4248]

Extraordinarily useful, affordable & doable -- such a super useful video. Thank you for sharing!

[@mxpimp47]

I would like to see some more on that custom base you made. Pretty slick, I need to make some my self. I have some tool steel laying around. Would be a good project. Great video as always. I learned something new.

[@mdshunk]

Clayton Miller There a decent plan for a surface gauge in one of the popular metalworking projects books.... I just forget which one. Sorry. Maybe someone will chime in. In any event, they're super cheap on eBay for used branded ones. If you build one, you'll pay more for snugs than if you'd have just bought one.

[@mxpimp47]

MDShunk oh I completely understand that I would spend more building on than purchasing one on eBay. I look all the time. And I have some rough ones that could be cleaned up that we’re in a lot of an auction I purchased. But at the same time I would enjoy doing a project like that.

[@thetrevor861]

As I expected, Joe is coming at it from a different direction. And as usual - nice one, Joe !

[@ctprjcstv3998]

You can also make three adjustable jacks and then set three zero points on the top side. Then it is possible to move the indicator at the top.

[@joepie221]

On large plates, top indication could be a reach issue. On towers, you have the whole plate to use from below.

[@algirdpatrick5048]

The surface plate obviously needs to be cleaned with sp cleaner and a lint-free cloth.The 3 jacks and the surface-gage need to be " rung-in " on the sp.

[@vladimirbenishek5521]

Hi, I am wondering how you can be sure that the surface of the granite is satisfactorily even and does not affect the flatness measurements (because you are moving the instrument stand on this surface)? As far as I understand, the granite surface represents some kind of reference plane.

[@joepie221]

Based on the grade of surface plate, its certified as a flat surface. Unless it sees aggressive and continuous use, you can trust it to be reliable.

[@divermike8943]

There are several KZbin videos on how to inspect a surface plate and correct it if it is not within spec. But most shops hire someone who specializes in that. It is interesting to see however for knowledge on that.

[@divermike8943]

Looking at other videos I have come to the conclusion that isolating parallelism errors from flatness errors is not easy. Theoretically impossible but practically doable within a tolerance. The plane u make with 3 pts might be parallel to the granite surface plate. But it might not represent the best fit average plane for the surface u want to inspect for flatness. One of your 3 pts could be on a high or low spot on the part. I THINK u need to try several inspections using different sets of 3 pts for that plane. Each time u would get a different maximum out of flat reading. The one with the smallest maximum would be the best fit parallel plane to that surface and that would arguably be your truest flatness. The others just also have more parallelism error on top of the flatness error. Sound correct?

[@joepie221]

Multiple test are not a bad idea, but if your surface plate has low spots, you need to address that. Rotating, and re-checking a thin, large diameter round part is a good idea to see if it is warped.

[@xxxyyy7252]

Technique is called: Isolating the plane. Classic way is to use 3 jack screws. Same height 3 stands is a variation. Watch this: kzbin.info/www/bejne/nF6lnWBoebmckMk

[@Steve_Just_Steve]

Great idea! This got me thinkin, if you don't have towers you could put a ball bearings on 123 blocks with holes. Seem like it could work if verified and have a smaller contact area than block alone.

[@sjb_rnd]

Hey Joe, I've used precision ball bearings on matched 123 blocks as a similar setup. The ball bearings were very consistent diameter and I found three holes on the blocks that were very close on height. I really like your three post design. It gives more room to work and easy to setup. Maybe one day you can show an example on how to lap them to be the same length?

[@superdansilverman]

Stephen Brown are the holes chamfered to a precise depth? otherwise the balls would sit at different heights unless I'm missing something.

[@sjb_rnd]

My csk are the same depth. Just compare the ball heights like he did using an indicator to check them first.

[@wernerberry7800]

Well done Joe! Thanks for sharing!

[@bcbloc02]

Good tip. Normally I would just transfer blue it to check flat but this gives you a measured number in case you need it.

[@aceroadholder2185]

His method does give the actual deviation so that a "is it close enough" judgement can be made. Blueing almost works too well... you know where the high spots are, but would you be better off to re-machine or would grinding or lapping the work to obtain the required flatness be the fastest way to get what you need? I've found that unless the material has been stress relieved (especially cold roll and stainless steel) it will squirm every time you skim material off the face and it may not be much better than when you faced it off the first time. It doesn't move much, but if being really flat is important (which is why you'd be checking for flatness in the first place) it can be a problem.

[@wyldanimal2]

At the end of your video, you touched on using 1-2-3 blocks. Using a Steel Ball in one of the holes of three blocks, gives a minimal 3 contact point on the part. Just qualify that the tops of the three steel balls are the same height. edit: I just read more of the comments, and see that others have made the same comment..

[@alandolphinrowland4393]

When measuring the towers as soon as you move the finger clock to a new position the next value is already null & void. If you were an inspector then each tower would be slid under the clock to register a true reading from the surface plate. If you were checking to a specific length over the towers then the clock would have been zeroed on a slip pack first.

[@joepie221]

I'd argue either method is valid. Just don't load the indicator into the pivot. Since the indicator will sweep for this method, moving it isn't a problem. Always sweep under or away. And a correction for your comment. I am looking for a constant value for each tower, I am not measuring them.

[@ChrisB257]

Another gem Joe. :)

[@lucianovasco4654]

Muito bom mesmo. São os jeitos antigos que sobrarão no final.

[@ronpeck3226]

Thanks Joe, Always a treat!

[@outsidescrewball]

Thanks Joe...great lesson and I watched Dan G video as mentioned in one of the viewer comments along with your comment....ATB

[@jy6174]

Thanks Joe , very nice explanation

[@Maxi-hs5nk]

can you not use a proven straight edge or parallel or feeler gauges on the surface and look for wobble or light? I am missing something?Thanks for the vid Joe

[@5954ldydi]

Maxi77 This seems more of an exact way to not only tell if it is unlevel but also by how much. Although I may be missing something. 😋 Hopefully Joe will see and respond to your question.

[@joepie221]

A proven straight edge would probably work if it crossed center and you checked in multiple radial increments. Over the course of my career, this method proved to be the only one the inspectors couldn't argue with. Shimming and leveling is also certainly an approach but would take more time to setup.

[@Maxi-hs5nk]

Thanks Joe for the reply, always learning :-)

[@erikisberg3886]

I really like Your design of the support posts! Will make a set of these. I have been using 3 gageblocks the same way, but as You point out, it is less than ideal to support the piece at the edges where machining burrs and other errors are most likely. I also think the flat top is better than balls since the setup will be more rigid and support the piece better for accurate measurements. Perhaps I missed if You mentioned the ease of measuring parallellism with this setup by indicating the top surface as well, which is another advantage of the method. Thanks again for the idea!

[@rathcorn]

Lol the face in the corner, lol, I don’t usually watch this stuff but, I’m now interested into it.

[@joepie221]

That just showed up one night. I'm afraid to erase it.

[@Seek_Peace]

Just watched one of those "shorts" where someone shows doing this with 3 screw jacks calling it "old school method" and I thought there must be a better way, and of course Joe Pie delivered, thanks for sharing your knowledge Joe, it's a resource that keeps on giving.

[@FredMiller]

Brilliant! So simple! So accurate! Thanks Joe!

[@worthdoss8043]

Thanks for yet another informative video Joe. I have a question to ask and a suggestion at the same time.. Do you use a height gauge and you surely do, could you do a video on the many wizard like uses of one? It seems for some reason to be a neglected instrument. I use mine one way to set the height of my cutting tools on the lathe, the number (3.781) is wrote down on the splash guard so I wont forget it. You or anyone else here would laugh at my granite surface plate but it works for what I do at home. It is polished granite siding from a building in downtown Austin I checked out for flatness with a straight edge and a strong light behind it. Not lab quality but darn flat and works for the stuff I do as said. Again thanks. Worth .

[@josefrefuses2go694]

I second that request Joe!

[@johnspargo5876]

Cunning. Devious. Thank you from John Spargo in Cape Town

[@ralphwaters8905]

Very nice and simple, great for smaller items like checking the cross slide on my lathe. I wonder if you would want to stand that surface plate on edge to check something larger like an engine block? Also, stuff I was sort of expecting to see some Prussian Blue paste. Can you comment on when this would be appropriate in terms of accuracy, or is this just used in scraping?

[@markcnc]

so i was like, how the heck is he going to tell which side is out if indicating from the top show something? did not see that coming. Always great info Joe, what will you show next ? ....hmmm ? ..... ? .... ?

[@joepie221]

I plan to attack cosine error when indicating. I'm fired up about this one.

[@michaelhart4075]

20yrs exp....I was taught the same methods as shown. But if you listen when he puts the part on home made blocks he even said he is still checking for parallelism. He is checking the parallelism still from the table to part. The only way i see to do this is put the block and indicator on the surface itself you are checking and move it around to see the highs and lows. This would only work with a large surface area.

[@salvadorebertolone]

i was thinking about this with 123 blocks, and then drilling them to hold a ball bearing on top. im not sure how much variance i would get using the drill hole diamater to locate the vertical plane of the ball bearing, maybe boring it, or regrinding the top of the block to adjust their height to each other.

[@EmmaRitson]

so much to learn. thanks, for such a clear explanation!

[@joepie221]

Thanks for watching. Now send me some of your warm weather. Its in the teens here. Rare for Texas.

[@johnbodmer5645]

Great Idea Joe!!! I must make some towers for myself.

[@georgegreene3685]

Go Air Force! Great video, I need to make some of those towers for flatness demo in class. Thanks for sharing.

[@TJF2005]

Great video, what material are the towers made from?

[@glennschemitsch8341]

I would think that optical flats are the best, but flatness can be a very controversial issue. If supposedly light can bend, then ........you can see where this is going.

[@JohnnyRabbitQC]

I will make a set of towers like this, to much hassle to set the height with the screw jack style towers. Thanks!

[@niltonpolydoro1]

Very nice video. Congratulations from Brazil. Nilton Polydoro

[@David.Munson]

Can I use my wife's granite counter? Great video... Your the smart uncle I never had.....

[@drazenkosutic]

Hi Sir, is there some reason that the top parts of the inspection towers are flat and not spherical? Would it be ok to have a small steel ball (from a ball bearing e.g.)?

[@JaakkoF]

Flats average the machining surface finish and balls have the tendency to squash under the weight of the workpiece and also the tendency to go into the workpiece under the weight.

[@drazenkosutic]

Thanks for the reply, it got me thinking.

[@HungNguyen-qv4qn]

Hi Joe, I have a question what if I have a part that too small that can not use this method to check flatness ( part too small to put in jackscrew) , can I just put it on a gauge block then use indicator to measure flatness??? Thank you.

[@joepie221]

You would have to trust the area making contact with the gage block is flat and only check the overhang, but you may get lucky.

[@benlonghair]

Joe, my teachers have told me bunches of times to always move the part, not the indicator. Do you have any thoughts on that?

[@dwaynebanville8549]

i'm just guessing but your teachers never had to move a 125lbs part . .

[@deeremeyer1749]

In the "non-precision" world of engines and engine parts a simple straight-edge, feeler gauges and flashlight work great for checking "flatness". And by "straight-edge" I mean a straight-edge" with an actual "edge" rather than a "face" several inches wide.

[@joepie221]

Your method will only indicate linear flatness ( straight line ), not planar ( large surface )flatness. They are 2 different conditions.

[@chrisn3794]

Any tips on reamers? Always seem to get a crappy finish.

[@felixar90]

Never reverse a reamer, even a manual one. It dulls them. Uh... Don't take more than 0.005". Ream immediately after drilling without moving anything. Lube that shit up. Maybe your reamers are bad?

[@joepie221]

Chris N Thats a very open ended question with many variables. Material, RPM, lube, depth of cut, type of hole, type of reamer etc. My depth of cut is usually driven by the diameter I am reaming and the rpm should be much slower than the drill.

[@billdlv]

Good tip.

[@tinkermouse-scottrussell3738]

Thanks for sharing Joe, something I can use in the future.

[@proctor1234567890]

Thank you

[@PowerScissor]

Is there any way to check flatness alone? Been watching videos for days. Everyone seems to have these large expensive certified known flatness surface plates and then check vs the known flat. As just a hobbyist, is it not possible to check flatness without having someone else make something flat and then compare to thst surface?

[@5eZa]

use a straight edge and a flashlight behind it, and/or feeler gauges. or use the 3 plate lapping method to make your own flats

[@TactlessWookie]

3 dislikes? How can anyone not like Joe's wisdom?

[@desertforgeknifetool2142]

Dont even try to figure it out. They are A-holes. Joe is Awesome focus on that!

[@merlinmagnus873]

Vampires hanging upside down from the ceiling watching his vids. They think they are hitting the like button and wonder why so many people dislike his vids.

[@xxxyyy7252]

There are legit reasons to give thumbs down. But psycho-fanboys will not understand.

[@paultrgnp]

xxx yyy Try me..... I am open to logical argument.

[@JDLuke]

The argument was, and I'm not even kidding: "Joe is bragging like he invented this technique".

[@jstirling1209]

Very good idea.

[@akukorhonen5182]

How about putting some steel bearing balls in the holes of 1-2-3 blocks to makeshift pins? Measuring them after that of course, for the exactly same height over the balls.

[@freddepauw]

good alternative option..

[@PeregrineBF]

Won't sag be an issue eventually, making this unsuitable for large or thin parts?

[@joepie221]

If it would sag at inspection, chances are it would conform at installation and a flatness spec would be unnecessary in my opinion. I have checked 14" rings this way at .3 thick without gravity being an issue, but I can see your point.

[@BigEBikes]

Would a leveler suffice?

[@5954ldydi]

Awesome video! 😋

[@AgentWest]

Thank you for the video. As for 1-2-3 block, use three ball bearings in the holes of the blocks. Or if you don't have Swiss Cheese blocks, use flat ones. Put a plain hardware washer on the block and set the ball bearing in it. The washer would only be there to keep the ball from rolling away, so make sure there's free play.

[@iangraham6730]

You are watching a professional!

[@nevetslleksah]

This is a great video and a great idea. But here’s my issue. My old lathe will not face a large diameter perfectly flat. If I face a workpiece about six inch diameter then put the machined surface down on my surface plate it will spin like a top so the center is high (convex). I assume my cross slide must not be perpendicular to the lathe centerline? What is best way to improve this condition (besides getting a new more expensive lathe)?

[@TactlessWookie]

While that is possible you may also be seeing creep in your compound along the leadscrew. One thing you can do to check is to use a crossslide lock if your lathe is so equipped.

[@RobB_VK6ES]

you may see the same symptoms if the headstock is misaligned also.

[@nevetslleksah]

chris0tube - Chris and others, thanks for all your tips, but I think my lathe is facing OK now. I recall one time last year discovering the saddle gib was loose and there was about .020” movement front to rear. I adjusted the gibs. Today I took a 6.5” diameter piece of 6061 aluminum and faced it off to clean up all the way across. My Starrett straightedge and eyes say it looks flat and a dial indicator on the lathe cross slide reads zero from outer edge to center. Disk feels good laying on my surface plate. I have not yet built a set of inspection towers per this video (but my carbide balls arrived from McMaster today) but plan to check with an indicator per this video. Thanks for all your tips on what might have been ailing my lathe. Guess I’ll keep the old gal.

[@cogentdynamics]

Joe, I have been told it is better to move a part under the indicator vs moving the indicator over each part (I'm thinking of the towers you showed)? Any thoughts on that? Thanks again for making such informative videos!

[@joepie221]

I would respectfully disagree with that. the towers assure 2 parallel planes, and the part being parallel to the surface plate. Sliding the part under the indicator may give a false reading on a flat part if its not parallel to the other side.

[@SoWe1]

@@joepie221 I think he meant while checking "downwards", he wants to have the base with the indicator stationary while you drag the "towers" underneath them - there is no "other side", the tower is on your granite plate and you're checking it's heigth

[@alessio55555]

what criterion do you use to choose the three points?

[@neilkitzler9268]

Would checking the part with an indicator on the machine work after surface cutting it? Or is this mainly for the person doing the first article outside the machine?

[@joepie221]

A part still in the machine is still under the load provided by the chuck or vise. It is better to check it on a surface plate free from clamping pressure.

[@909sickle]

How do I know if my granite is flat???c

[@joepie221]

They usually are unless they have been terribly abused. I believe you can find videos on the subject if you search.

[@MrRctintin]

Great tip as always. Is there a set of drawings available Joe to make an adjustable dti stand like yours? Loving the thumb screw to move the dti into place.

[@joepie221]

Made that as an apprentice some 40 years ago. The drawing is long gone. Maybe I'll re draw it.

[@MrRctintin]

That would be great if you get the time fella. Thanks.

[@hardcase1659]

Don't take this the wrong way, but this is a pretty straight forward part o make. The dimensions aren't even critical except the length of the pieces and parallelism of the top and bottom surfaces.

[@doright6461]

You can even make a round base relieving the bottom face to about 1/4 or whatever from the OD so it will continue to wear flat throughout use.

[@MrRctintin]

It’s the mechanism with what I guess is a compression spring that the thumb screw attaches to that is like to a close up of.

[@nikhilk8457]

which surface need to butted on surface table, the surface which we measure or opposite for flatness inspection?

[@joepie221]

In this setup, you are checking the side in contact with the pins.

[@FrenziedFruitcake]

I've seen another method where you use 3 jack screws and adjust each one with the indicator over it to zero. This creates a plane between the 3 points and you can now sweep the surface from the top side. Is there a downside to this method?

[@joepie221]

Only the time it takes to adjust the screws. Otherwise, it should work the same.

[@ugd240000]

your videos are great

[@MrFlyingB]

All well and good if you have a lathe or mill to make the known piers to set the part on. Why not just put it on a lathe and use your dial indicator if the lathe is true?

[@joepie221]

If you make a part like this, you do have a lathe right.

[@joepie221]

Plus, a chucked part under tension may exhibit a flat reading if you sweep the face in the lathe with an indicator. Only in a relaxed state is a true reading trustworthy

[@huagangyan1449]

we can mannufacture a variety of granite surface plate with high precision.

[@robertoswalt319]

Pure genius. I learn something good from each video.

[@xxxyyy7252]

Not "genius". It's a standard technique in metrology.

[@robertoswalt319]

xxx yyy It may be a standard way to perform a measurement but for a noob to metal working like me, the process is incredible.

[@donnelhuddleston2478]

Thanks for that one.

[@gregkinzebach2040]

Would it work to use jack style stands under the part and create your 3 point level plane on the top and take your reading? Or is that checking parallelism

[@joepie221]

I don't see why that wouldn't work. you just have to be sure the resting surface of those stands can be trusted or the reading will vary as you sweep.

[@gregkinzebach2040]

@@joepie221 thanks for the great videos!

[@rayfletcher8759]

Got another question: how are you not simply translating the plane of the granite surface plate to the plane created by the 3 points on top of the towers?

[@joepie221]

Thats exactly what is happening. Allowing the indicator to pass between them for inspection of the registration surface.

[@11Aldebaran11]

Hi there Joe, another great video goes in my educational library. Actually I was searching the KZbin to find someone and show me, how to test my Granite if it's true flat. You see I don't have any true flat surface so I can use it as reference. Do you have any method to do that. Thanks anyway. Keep walking (I mean videoing)...... :-)

[@spencerr505]

You can check out robin renzetti's video on lapping his surface plate flat and how he checked for relative flatness with a precision level. kzbin.info/www/bejne/bJ-8aKiNZtp6b9U

[@11Aldebaran11]

OMG, this is a very complicate and sophisticate procedure, I just need to check my 45x45x4cm granite if its true flat, to be a trustful tool for me. Anyhow thanks for the try.

[@kimfucku8074]

This is usally done using highly accurate electronic inclination measuring sensors in a temperature controlled environment. Check out wyler.com/en. They produce such plates and the sensors.

[@hatersaywhat8986]

Another great "online store" item. Doors a knocking

[@cpeterson4290]

where can you buy these?

[@rayfletcher8759]

Is it more accurate using only 3 towers instead of say four?

[@joepie221]

3 towers will never rock on an uneven surface. Stick with 3.

[@ralphwaters8905]

In the world of geometry, 3 points will define a plane in 3D space. Any other number will defeat the strategy, just like a shopping cart with 4 wheels often has one that's shorter and wobbles.

[@thatsthewayitgoes9]

I'm never sure how to turn relatively large diameter but thin (say 3/4" - 1" wide) discs , so that the faces are square with the O.D. . I usually just rotate & wiggle the disc in the jaws as I carefully tighten the chuck jaws down onto the O.D. - hoping the jaws will pickup the outside diameter and square the part to the squareness of the jaw surfaces... But, I don't think this is the best way. Anyone have a good way to do this? As example: a round CRS work piece 6" O.D. x 1" with both 6" surfaces saw cut ( not flat, not parallel ) . How would you turn to true up each face so they are parallel with each other and square with the O.D. ( total unparallel / square .002" over the 6" )? thank you. Roger Williams, NorMag Gunsmithing, Fredonia WI

[@joepie221]

Floating in a part as you have described is a solid way to allow the chuck jaws to help with the OD squareness to the face you are about to cut. If you can't turn the OD, it's just about the best way to do it. This video shows a setup that will help finish the backside if you don't use soft jaws. kzbin.info/www/bejne/i2TbaXtnjcdgoMk

[@thatsthewayitgoes9]

@@joepie221 Thank you Joe. You answered SO quickly. You confirmed with the method i use to 'float' the work piece to the jaw faces to get the disc aligned fairly good. AND, your video link was EXACTLY, not only the answer to my question; but, the stand-off tip was outstanding! I will be D/T some of my chuck faces. Your work, thinking process and your help to our community is beyond outstanding. thank you.

[@joepie221]

Happy to assist. thanks for watching.

[@eltigre6446]

Do you make the pins or are they available like 123 blocks?

[@joepie221]

I turned them , then ground all 3 at the same time for accurate height match.

[@taystew]

i hope you dont mind my reference to Dan Gelbart's video kzbin.info/www/bejne/majHoIigrtOje80m40s im guilty of spending too much time on youtube and think your demonstration is a good accentuation of this 'reversal method' . no judgement passed on my end, but if someone needs related content i think this needs to be in the comments.

[@joepie221]

He gets to the point towards the end and I totally agree with his presentation. However, his method, in my opinion only, seems way more applicable to a linear measurement as opposed to a large planar surface such as this. It almost seems you would need a computer or CMM to evaluate all the data points collected to come to a conclusion. Thanks for pointing me there.

[@armdaMan]

Another great "how to" Video, Cap'n. Brilliant Thanks a stack for taking time to show and share. ATB aRM

[@jasnmar]

"Take your 3 pins, and put them in a 3 point shape" 3 pins are always in a 3 point shape :). Just giving you a hard time. Nice tips for checking flatness without "high end" tools to do it.

[@joepie221]

Busted. Keep me honest.

[@johnwinter9399]

I got confused, so you've machined both sides and the A B side is facing down when using the towers? If you had left one side not machined it would have made it very clear why this method works.

[@joepie221]

True.

[@TrojanHorse1959]

Great video Joe, thanks for sharing!

[@weslage]

You're checking parallel. You need jack stands on 3 points. Zero the 3 points to the indicator which would make it a flat plane, then move your indicator across the surface. Just an FYI

[@joepie221]

Doesn't a parallel reading to a known flat surface indicate the surface being checked is also flat?