Quint, these videos are absolutely amazing. I swear I've been checking RU-vid every 6 months for the last 6-8 years looking for good GD&T tutorials. Please keep going. There is so much to cover and you are doing an incredible job. I would gladly support your videos on Patreon or something if you keep pumping them out.
As a student going in to the second term of Machine Manufacturing Technology at PCC, I can honestly say that this video series is and will be like gold. The faculty members should consider having these added to the GD&T syllabus. Thank you!
I followed each and every video of yours & learned the basic GD &T clearly without spending a penny, thank you Quint for this post. I wish Our would have explaining skills like You.
The amount of effort put into this series is insane. Most people would have just done some nearly-good-enough computer animations. What a great thing to have made.
I finally understand what the heck is a [basic dimension] and why it's confusing. 0.) You still use the +/- tolerance for the hole feature "for size". So, if hole is too large or too small it's rejected. Now, we continue to the issue of "position". 1.) Basic dimensions is really a "short cut" to move the horizontal and vertical datum reference edges/surfaces to a single coordinate point[x], [y]. 2.) It's a "shortcut for calculation" and presenting the tolerance zone "for the hole center=hole coordinate" as a simple "datum point" and the tolerance circle. 3.) However, you still need a pin gauges and you still need to measure the x and y from the gauge to the datum edges for x and y.
I have to do a training session on GD&T, specifically position and bonus tolerancing for people with no real background in it and I think this is going to be a big help. thanks for doing these!
you prolly dont care but if you are bored like me atm then you can watch all of the latest series on InstaFlixxer. I've been binge watching with my girlfriend for the last weeks =)
I like what you show at 12:27. That is exactly the virtual condition for an internal feature(hole). Big diameter(that encircles red and gray circles)=drill hole feature range Red diameter=diameter from tolerance of straightness, circularity, true position,...etc. This in effect "takes up hole space". Gray circle=virtual "pin gauge" that can fit. Thus: Diameter(virtual condition, gage pin diameter) = hole diameter(MMC) - diameter(of slop like straightness tol) The hole analogy is a little "counter-intuitive" than the scenario of external features, because it get's smaller. For the external feature it's more intuitive, which is virtual condition = diameter@mmc(largest) + diameter(of slop)
Cool. I have been highlighted. This means I'm on the right track. There's no one at work who knows this stuff, so I can only rely on our friendly educated cyber community. Keep on.
Hi, I have a question I have a sketch of a structure composed of three sheets metal, one of them is used as based, and the others are above of this one, separates for a specific distance, these two have an orifice plate with the same diameter and they are concentrics. When the welding is applied to the structure, then the assembly will have distortions, and the two orifices plates won’t be exactly concentrics. I would like to know if there exist a minimum tolerance when you're going to apply welding between hole to hole? For any assembly with the same specifications. Something like a table, a thumb rule, handbook or any document that specify some specific tolerance.
I have used tolerances for límits and fits and I choose them base on what the book says now how do you decide the geométric tolerance for something? Is there like a rule or something?
Diameter of virtual circle = diameter of hole(MMC...the smallest) - diameter of slop(like straightness tol value at mmc). This may sound confusing, but if you draw everything out...but especially the gage pin(virtual condition) that will fit it will make sense.
So if I am not mistaken, shaft diameter + position tolerance = virtual condition and Bore diameter - position tolerance = virtual condition? Also, I am assuming the hole and the peg shares the same position tolerance at the dead center location. Is it possible to have two different position tolerances? Finally, does the term virtual condition simply means that that there is a theoretical or invisible point where the peg and hole makes contact? Sorry Im self learning.
So the position tolerance within a GD&T control frame is from one side of the bulls-eye to the other? Or from the middle of the bulls-eye (theoretical dead center) to the outer edge of the bulls-eye?
@@quintgdt8751 Why do they put the diameter of lets say .030 into a control frame if the part can only move from the theoretical center to the outer edge of the bulls-eye ( .015 ) in all directions? So a person always divides the location tolerance in half when measuring for quality control?
@@quintgdt8751 Right that is what I am doing now. I am putting a hole in a part and I will have to calculate the side of the hole to the edge of the part to find out if I am within the .030 which is in the tolerance control frame. And you are saying that number is the amount of movement BOTH ways from the center. Or the diameter. Even though the part is only allowed to move .015 in all directions to be in tolerance.
Amazing video, very informative. Are you able to do one on one GD & T training through skype. I know it wouldnt be free but I really need to get a clear understanding of how GD & T operates. Thank you in advance
One thing that I find that helps is to read "older" GD&T textbooks, because when it was first introduced in 84 they really tried to illustrate very useful sketches. In addition, really focus on terms and definitions. All the more recent textbooks try to "optimize" the written english language to be "lawyer tight"...which doesn't help beginners visualize a full/accurate mental picture.
How does one come up with the position tolerance itself? I know there is limits and fits for holes and shafts are there charts one can use to come up with the position tolerance itself thanks.
@@quintgdt8751 Thanks, If i may ask a fallow up question have you ever heard of using formula like the fixed-fastner and floating-faster formulas to get a simple position tolerance provided one already figured out the limit and fit. here is the formulas i'm referring to images.slideplayer.com/36/10590168/slides/slide_73.jpg
My experience in mfg is trial and error, but companies don't always learn and apply correction. My best case experience is as follows: 1.) R&D being so preoccupied with function of product assumes best case scenario of all the fastener joint position/hole sizes with tight tolerances. 2.) We get the actual parts/they don't fit/we break out the drills. 3.) If we have some time, we may actually carefully measure all the first article parts. 4.) The measurement data can now be easily calculated for average or mean deviation and compared to the drawing dimensions. 5.) Next time we design position and hole size we have a "real tolerance" to apply.
If you can commit to a range as stated at min 9:07, what if variation makes it so you cannot commit to that range? You couldn't commit to a bullseye but some how magically you CAN commit to a range that assures being acceptable?
@@quintgdt8751 I'm just trying to get to the heart of the explanation. Essentially what prevents going outside of any tolerance. What if the drill is accidentally set to repeatedly be on out outside edge of the bullseye? Then you'd still have many outside the red due to variability. And so on no matter how large the red bullseye is. Do you kind of understand my question? Thanks
Quint Crispin Rather than use GD&T on parts to make things fit, why not use it on the parts of the machines that cut and drill. Then you could just use basic dimensions on all drawings. Big money saver.
@@quintgdt8751 Oh right! I think what would help would be a video of sketch concept to CAD to manufacturing to verification of a part with a hole to show how position is verified and with another feature that requires A,B C datums. Showing how tolereances fail but GD&T succeeds in reducing scrap, etc.
