Really appreciate that you aren't just talking to slides, but getting your hands on the simulators and parts, taking measurements, and doing the calcs. Awesome demo with a hole that would otherwise be out of tolerance, but is in due to bonus tolerance.
If you could do more of this type of video, where you are actually showing the way these gd&t functions apply on real parts, that would be awesome, because I learn so much better than when drawing on a white board or something. Thanks though for all this unbelievably free information.
Thank you. MMC and LMC were FOS conditions that I had never fully understood on the practical level. This is the first video I found that has finally helped me understand those callouts.
God bless you! I am learning SO much from watching your videos!! I am starting a Designer/Drafter position at a gear manufacturing facility and I am learning and relearning all the information that I SHOULD have learned in college 15+ years ago! I am so grateful for your demonstrations and teaching and I pray that you are blessed for it!! Side note: I am returning to college at the age of 49 yrs old enrolled in mechanical engineering, and because of your videos, I believe I am learning at an extremely fast pace on the content you are providing as well! I already subscribed to your channel, and you will be seeing nothing but "likes" from me!
Professor, what will be the inspection procedure for the same example of postion control if we have RFS condition instead of modifiers. Will it be the same as you have explained, excluding the bonus tolerance part. Or do we have a different procedure altogether?.
Thank you for taking time and having the patience to teach. You have helped me understand in struggling areas. Some are made to teach and some are not. #TeamProfessorOdell
Thanks so much! I've never had a hashtag before! Good luck with your studies, if you have any questions about specifics, send them my way and I may be able to incorporate them into a video.
Hello Mr Odell, I am fairly new in this field but have great interest in it. I am having trouble with with one of my programs. I have two trihedrons on my CAD model. One set in the direction that is expected and it the other one I think is preventing me from running. I did not intend on two. In the same spot. #1 ZYX(the expected one) #2 XZY(in same direction X in Z axes, Z in Y axes, Y in the Z axes directions) I know I just confused you! Do you know where I went wrong?
@@rosalyncampbell5231 Hi, I’d be glad to help. What software are you using? I have a website if you type my name into google. Send me an email with any information you can provide and I will take a look.
OMG what a wonderful explanation thats what I am looking for u explained very well and also demonstrate with the actual part.Nobody can explain better than you I really appreciate.Thanks a lot
Thank you for taking your precious time to make this video! As a 25-year mechanical inspector I have done this process for many parts and programmed position on the CMM many times. This is the stuff no one knows anymore. We now rely on the CMM like it's a magic. It's as if there is no other way to find the position of features of size.
Excellent job! I would just like to point out that I believe that the tolerance zone applies through the entire thickness of the part. As far as I could tell, you only checked the location to one surface. I think that you would also need to make the same check on the opposite side of the part or make another check from the same side by moving out along the length of the pin a distance that is equal to the thickness of the material. Thanks again for all that you do to help understanding of GD&T!
Hi, After discussing your point with a colleague, I agree that you are generally correct in that both sides of the part should be checked to ensure the holes are perpendicular. I will mention it the next time I make an inspection video. I did look it up in "Dimensioning and Tolerancing Handbook", Chapter 18 Section 18.6.1.2. The author recommends 3D verification for holes longer than 1/2", but qualifies the 2D verification as a judgement call that involves some risk. Thanks for watching and commenting, I appreciate the great feedback.
Checking the pin height at the thickness away from the part would give you the inverse height of the other side of the part at it's surface right? Then you could use the x and y that is the further distance from the basic dimension to determine if it's in tolerance. This would also give you the perpendicularity regardless of thickness, wouldn't it? I'm very new to this so sorry if what im saying doesnt quite make sense.
So, I just want to summarize my understanding of this part of True Position Tolerance Measurement. a.) Get ØHole[meas]. Using pin gage that fits the hole with "tightest" pin gage & seats "square" on the datum/inspection surface. b.) Get X[meas] and Y[meas]. Using X and Y datum surfaces [ - B - ] and [ - C - ] to contact the pin gage outside surface. Then adding the pin gage radius value. "Thus, X[meas] and Y[meas] is effectively the value to the "axis" of the hole[meas]. So, now here is where a little calculations begin. c.) "modify" the true position tolerance value with the bonus tolerance. [modified] True position tol Ø = True position tol Ø + [ meas hole Ø - hole Ø @ mmc] d.) Get ▲X and ▲Y. Just subtract the X[meas] and Y[meas] by the X[basic] and Y[basic] that is specified on the drawing. "Thus, ▲X, ▲Y are distances only from the "center" to the hole[meas] center or axis. "Not distances away from the [ - B - ] and [ - C - ]. d.) At this point, you could "possibly" choose to plot a circle and a point. The circle = [modified]True Pos Tol Ø. The point = ▲X, ▲Y. To see if the point which is the center/axis of the hole[meas] lies in the [mod] True Pos Axial Tol circle. e.) However, an easier method which just requires the Pythagorean equation is applied. R^2 = ▲X^2 + ▲Y^2 Ø=2 x R This Ø is the Ø of the Envelope of the Axis of Hole[meas]. This is a cyl zone! f.) Now compare this Ø[ Axis of the hole[meas] ] to the Ø[modified True Pos Tol Zone]. Phew, that's a lot of text but I hope I specified the "english" accurately. I see the real problem with understanding this concept. There are two distinctly different Diameters Ø. The hole Ø and the Axis Ø. Both are specified in the drawing and both are measured. Actually, the Axis is not a Ø. The Axis Ø is a cylindrical envelope volume. So, not only two distinct Ø's, but we must not forget those Ø's actually apply to Cyl Volume Zones. Yikes!!! I need a CMM!!
Thank you very much for putting this knowledge available. I'm entry level on this subject and I find this extremely helpful. My only comment is that the sharpie writing gives me the shivers lol
Excellent! one other thing to consider if the same gage pin will be used for all holes. After zeroing the height gage on the surface plate, drive it up .1255 inch and zero it again! now you will have a center reading for each hole without the need to subtract the constant .1255.
I think the bonus tolerance should be calculated as soon as the pin gage is checked for size and perpendicularity. Thus, if pin gage exceeds the hole size tolerance then you can stop. If pin gage is within, then determine Ømmc. Then Bonus tol = holeØ - mmcØ Then, add that to the original specified T.P. tol. So, [mod] T.P. Tol = [specified] T.P. Tol + Bonus Tol. Then [mod] T.P. Tol, which is actually a Ø will be used for the final determination against the calc [meas] hole axial cycl zone Ø.
This video was tremendously helpful! I do have a questions though: I have some control frames with composite position tolerances. I understand the concept of what the intent is, but I haven't found an online resource that explains exactly how to measure them. I basically need the last 5 minutes of this video (where you go over the exact calculations required to qualify a part, but for the FRTZF of a feature control frame. Any suggestions?
Hi, I am working on a video to address your question. The short answer is that if the features pass the lower segment to the upper segment DRF, the part is good. It’s only when that does not occur that the segments need to be verified separately.
Using a gage pin does not check the size of the hole, it checks the VC condition. ASME Y14.5 says parts are to be inspected in a free state unless otherwise specified. Also, you cannot change the setup part way through the inspection, unless you start over. Thanks for explaining about the orientation of symmetric parts, this is a concept people often seem to struggle with.
Hi, the size of a hole is supposed to be based on 2 point measurements of local size like you mention. I would argue that it is very common to check hole size with gage pins and it is functionally accurate. I could see there being an issue if there is a potential wall thickness breech that a 2 point check might catch. I agree that parts are inspected in the free state by default, but there has to be some force applied to make sure the part is contacting the datum feature simulators in the correct order of precedence. I would argue that the part I am measuring in the video is rigid and not affected by light clamping pressure, where a floppy gasket would be treated differently. I change the setup to access the height gage from the plate. When I move the part, I reset it in the correct order of precedence so that the measurements will be repeatable by myself or anyone else checking the same part. Thank you for your feedback and input!
@@RDeanOdell Actually, using a pin which checks the VC of the hole is more restrictive than what ASME states. I think ASME botch Bonus since the size of the hole at each cross section does not account for imperfections in the form of the hole. It seems that Bonus should be based on the VC condition to assure assembly. I still have an issue with this inspection. I don't see any way that the gage pin is perpendicular to the primary datum plane. The tolerance zone for Position is a cylinder which is perpendicular to the primary datum. If the pin were set in a hole perpendicular to the primary datum, then finding one point would assure that a mating part such as a screw would assemble. When the pin is fit into the hole, finding one center point does not check the intention of Position. The single point could be spot on, but the axis could be angled such that a point on the side contacting the primary datum is out of tolerance. Using a VC pin needs a second point checked, either somehow find a center point on the other side of the part (challenging) or find a second point further from the top surface so you can trig out the angle of the pin relative to the datum. This way you know that both ends of the actual mating envelope are within the tolerance zone perpendicular to the primary datum.
Thanks @Dean for the video. I've a question, since the hole is positioned at MMC we could have used virtual condition to check the hole position right? My second question was, is there any options to use virtual condition gauge pin for LMC modifier of a hole?
Can we get a similar process involving a measurement of a hole position with a datum being a slot midplane with a MMB modifier? Cause I really can't figure out what is an implication of a MMB modifier in such case.
What to call this type of mating envelope, is it unrelated type in which the axis is not perpendicular to primary datum or is it related type where axis is perpendicular to datum.
Is the orientation aspect of the position tolerance considered neglible? I'm asking because the measurement is based on a single sample point on the gage pin for each hole.
He answered that in Chris Sherkel's comment: you really should check the position in two points along the axis to make sure the length of the hole lies completely within the position tolerance zone, but for short holes, sometimes people skip that check.
Great vids. If I have access to a height gage that will measure the ID of the hole I wouldn't need the gage pin right? Just measure the ID and the distance to the plate?
Hi, great question. The gage pin is used to capture the actual mating envelope of the hole. This makes measurement of the axis possible. I will address the measurement of the surface of the hole to the surface plate in a future video. Thanks for watching!
Hi, I meant the maximum pin gage that actually fit the hole I was inspecting. I tried a few different pins from my set, and .251 was the largest, ergo that is the MMC size for that hole.
so if the tolerance is 0.007 and the number is greater than that it is ok? so the calculation you added to 0.001166 was good and the MMC you added after is just to show us what you do if it was under 0.007?
Hi Mr. Odell, I have a question about the formula. So to get the deviation of X,Y you will get the actual measurement number then subtract the basic number or do it opposite way ? I'm getting confused because some of the sources ( from the books, internet) gives me the different information. Some say basic number subtract actual number. Thank you
Hi, It doesn’t really matter as long as you are consistent about which one goes first. You are looking for the deviation from true position, so the sign usually doesn’t matter.
It’s the Pythagorean theorem, arranged to solve for the hypotenuse, which gives the radius. We multiply that by two to reach the diameter of the tolerance zone consumed.
@@RDeanOdell Hello RDean 👋, i work for a company here in india, we supply plastic parts to AGCO,the same company that makes Messy ferguson and fendt tractors,they have highlighted positional issues with the parts we have sent, I'm not good at GD and T, hence i saw your video on positional tolerance to understand their concerns, there's a long way for me to go and your video helped me also thanks for the response, appreciated
